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Eruption and decay of the permanent teeth in primates.

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TEE
PUBLICATION OF THIS B S B a B C H WAS FINANCBD IN P U T BY
CARLOS F. MACDONALD
RSSEARCH FUND”
“Tax DOWB
ERUPTION AND DECAY OF’ THE PERMANENT
TEETH I N PRIMATES
ADOLPH H. SCHULTZ
Laboratory of P h y k a l Anthropology, Johns Hopkind University
TWENTY-ONE MQUBES
INTRODUCTION
Comparative investigations on the morphology of the teeth
in primates are much more numerous and extensive than are
studies dealing with the eruption, wear, decay, and loss of the
teeth. I t is the purpose of this paper to contribute new data
on what may be termed the life history of the teeth of primates. Information on this subject is very much needed in
order to demonstrate t o what extent eruption and decay of
the human dentition follows the rules prevailing among primates in general and how far the conditions in man may have
become altered in response to human specializations.
The writer’s interest in these problems started many pears
ago during his earlier comparative studies on the growth of
primates, when it became necessary to estimate the relative
or physiological age of monkeys and apes. Such age estimations are based in part upon the state of eruption or upon
the degree of wear of the teeth. It soon became evident that
the reliability of conclusions in regard to age from even the
most careful examinations of the dentition must remain very
limited until we are in a position to make fewer assumptions
and, instead, actually know more about the relative age and
sequence of eruption of the teeth in different types of primates.
489
AMERICAN JOUBNAL O F PHYSICAL ANTHROPOLOGY, VOL. XIS, NO. 4
JANUABY-MARCH, 1035
490
IIl)OLPH H. SCHULTZ
Facts for the solution of these problems can be gathered
chiefly from two sources : periodically repeated examinations
of the teeth of living primates and observations on the teeth
of large series of dead specimens of differing ages. Both
these sources were utilized by the author, but opportunities
f o r dental examinations on living monkeys and apes are scarce
and the study of dead material is limited by the fact that
most collections contain relatively few skulls of juvenile primates. For these reasons, as well as on account of the very
marked variability of some phases of tooth eruption, the
observations recorded in this paper are at times only fragmentary and in part permit merely tentative conclusions.
This study started with and emphasizes the collection of
new data bearing upon the relative ages and the sequence
of eruption of the permanent teeth in different primates.
Material for a corresponding study on the deciduous teeth
is not yet available in a sufficiently large amount to justify
more than a few preliminary and generalized statements.
During his examinations of various collections of skulls of
monkeys and apes, the author has recorded all deviations
from the usual and normal condition, i.e., all cases of variations in the number and, position of teeth and all instances
of pathological changes in the teeth and the alveolar processes. These data are in a sense a mere by-product of this
study and are presented, without going into many details,
as a basis for the evaluation of the corresponding conditions
in man and in order to complete the picture of the fate of
the teeth during the lives of their simian owners.
This investigation does not extend to the sub-order of the
prosimians because the accessible material is too scanty,
particularly in regard to juvenile specimens, for the establishment of representative averages. In an attempt to recognize and demonstrate the role of a simian heritage in the
life cycle of man’s teeth, this exclusion of all Lemuroidea is
a negligible factor because these primitive primates are unquestionably far removed from that part of the entire primate
family tree to which man must be assigned.
ERUPTION AND DECAY OF TEETH IN PRIMATES
491
The literature on the eruption, irregularities and decay of
teeth in primates has been consulted and is quoted wherever
comparisons with the author’s findings seemed desirable. It
will be noted that, unfortunately, there exists a considerable
number of more or less significant disagreements between
the writer’s results and those of some other investigators;
these will be discussed in their proper places, though in some
few instances it is impossible to suggest any possible cause
f o r such discrepancies beyond the general statement that in
the study of eruption of teeth one deals with a variable process
and that the frequency of diseased teeth can apparently differ
within wide limits in different groups of the same primate
genus or even species.
All the new data obtained by the writer are presented in
such a manner that future investigators of additional material
will be able to combine their observations with those recorded
here and thereby will be in a position to base their new conclusions upon more ample evidence. Certain reports on primate
teeth could not be utilized, because their authors failed to
state whether the particular conditions discussed had been
observed in one or in a great many cases, so that it cannot
be decided whether they were describing possible exceptions
or well-founded rules.
MATERIAL
The new data regarding the absolute ages of eruption of
the permanent teeth are chiefly based upon t.he author’s observations on the growth of ten living rhesus macaques, born
in the Carnegie colony of these monkeys, and of two living
chimpanzees, kept at the Department of Anatomy of the Johns
Hopkins University. The author is greatly indebted to Dr.
G. L. Streeter and Dr. C. G. Hartman for having been given
the rare opportunity to follow the growth of these macaques
of known ages. These studies will be continued until more
animals have acquired thetr full permanent dentition; data
on tooth eruption in these macaques, appertaining to a shorter
average period of growth, have been published by the author
(’33) in a previous report.
492
ADOLPH H. SCHULTZ
In addition, it has been possible to make a few scattered
observations on the age intervals between different phases
of the dentition in various living primates, examined repeatedly at different times, and on the state of the dentition
in a few other primates of actually known age. F o r these
opportunities the writer is indebted chiefly to Dr. H. Fox of
TABLE 1
List of primate skulls emmined in the direrent eollectiona
YUSLEY
DOXPABA
TNX
ZaOaLWY
HdRVABD
u. 8.
BIOYUSXUY
aOGIOAI
SUEVZY
COLLEGZ
Gorilla
Pm
Pongo
Hylobates
50
31
75
135
Pithecus
Papio
Lasiopyga
Colobus
Nasslis
Pygathrix
237
52
201
61
43
316
Ateles
&bus
Alouatta
Saimiri
Oedioomidas
Total=
I
32
52
70
18
17
1390
..
259
108
17
16
..
..
..
..
12
36
1
10
5
16
..
..
..
..
..
10
94
..
492
38
..
I
..
..
4
8
..
..
..
..
..
..
..
..
..
..
26
19
39
..
3..
8'
..
PHYSICAL
ANTEEOPOUXIY
ABOMTOBY
HOPXIrr8
UNIVERSITY
:OLLXCTION
A E.
SCHULTZ
TOTAL
12
28'
1
6
'
2
7
2
13
323
212
95
170
60
11
6
233
24
26
3
1
3
542
123
234
74
48
336
1
10
141
71
169
53
10
757
200
156
286
71
38
2908
..
..
..
..
1'
137
..
'Including
15 specimens loaned by Field Museum, Chicago.
Including some young embalmed specimens.
the Zoological Park in Philadelphia and to-Dr. W. M. Mann
of the National Zoological Park in Washington.
The largest part of the data to be discussed are based upon
the examination of the dentitions of the skdls of primates
in the collections listed in table 1. For having been permitted
to study the primate material in the different museums the
author wishes to express his sincere gratitude to Mr. G. S.
Miller, Jr., Prof. T. W. Todd, Mr. H. H. T. Jackson, and
ERUPTION AND DECAY OF TEETH IN PRIMATES
493
Mr. H. J. Coolidge, Jr. The enormous and splendid collection of skulls of wild gorillas and chimpanzees in the Hamann
Museum of Anatomy and Comparative Anthropology proved
to be of particular value for these investigations, since it
contains such large numbers of specimens with incompletely
erupted dentitions, as well as of really old specimens.
The names of the genera of the primates in table 1, as well
as the names of the species mentioned in the text, follow
consistently the convenient and well-known review by Elliot
('13). The first four genera in table 1 represent the higher
primates which are unquestionably much more closely related
to man than any of the lower forms. The genus Symphalangus has not been included, because no sufficiently large
series of skulls of particularly young animals could be obtained. The following six genera are Old World monkeys,
the first three belonging to the subfamily Lasiopyginae and
the last three to the subfamily Colobinae. The last five genera
in table 1 are New World monkeys which are distinguished
from those of the Old World by possessing three, instead of
only two, permanent Premolars on each side of each jaw.
The last genus (Oedipomidas) belongs to the family Callithrichidae which is characterized by the lack of third permanent Molars.
The total number of 2908 primate skulls examined contains
2394 wild specimens, killed in their native habitat, and 514
captive specimens which had lived for varying and in most
cases unrecorded periods under more or less suitable conditions in captivity. All these skulls possessed at least two
of the permanent teeth, the comparatively few younger specimens in the collections having been omitted in this report.
The permanent dentition is incomplete, or even the last teeth
are not fully erupted, in 982 skulls of which 587 are wild
and 395 captive specimens. This is the material used for the
study of the sequence of eruption of the permanent teeth.
Among the remaining 1926 skulls, in all of which the permanent dentition is completely erupted, there are only 119 captive,
whereas 1807 wild specimens.
494
ADOLPH H. SCHULTZ
EXPLANATIONS
It is necessary to define the exact meaning of some of the
terms, as used in this paper. In most instances considerable
time elapses between the first appearance of a permanent
tooth and completed eruption, as indicated by accomplished
occlusion. In living or in embalmed primates a tooth is recorded as erupting not when merely the first, small, white
tip of a cusp appears through the gum, but rather when the
entire top of the crown has just pierced the gum, though the
tooth is still far from functioning by meeting its antagonist
in the other jaw. In the skulls of primates a tooth is considered to be erupting when the uppermost portion of its
crown reaches clearly above and not merely to the alveolar
margin. In many juvenile skulls one or more permanent
Premolars can be seen underneath the corresponding deciduous molars which are evidently almost ready to drop out.
Even though a Premolar actually projects above the alveolar
margin, it is not counted as an erupting tooth until the deciduous molar to be replaced has definitely lost its hold by even
the last of its roots.
In the relatively few cases in which the right and the left
halves of the jaws differ significantly in regard to the state
of eruption of the teeth, the side with the more advanced
condition is utilized for recording.
The state of attrition of the teeth has been noted on each
skull and it was found that it suffices for the present purposes
to divide the various degrees of attrition into only two general classes, designated as ‘slight’ and ‘much.’ All cases in
which the degrees of attrition of the permanent teeth range
from no macroscopically visible signs of wear to at most very
moderate wearing of the crowns of usually only the first
Molars, Incisors and Canines are placed in the group of skulls
with slight attrition. As soon as more than the just-mentioned teeth bear readily noticeable signs of advanced attrition, accompanied by at least partial exposure of the dentine,
the cases are included in the group with much wear of the
teeth. This, as most classifications, is somewhat arbitrary,
since a small percentage of the specimens could with equal
right be assigned to either of the two classes. Only after
ERUPTION AND DECAY OF TEETH I N PRIMATES
495
considerable experience is the observer in a position to make
consistent decisions in all cases in which there is any doubt
regarding the degree of attrition. For this reason the writer
reclassified his first 260 records after all the other material
had been examined, changing ‘much’ to ‘slight’ wear in
eighteen cases.
The primate skulls have been divided into three age classes :
‘young,’ ‘adult’ and ‘old.’ All skulls with permanent dentition started, but not completed (including cases in which all
permanent teeth have appeared, but not all completely
erupted), are classified as ‘young,’ all those with completed
eruption of all teeth and with open base suture (synchondrosis
spheno-occipitalis), or closed base suture, but only slight
attrition of the teeth, are classified as ‘adult,’ and all those
with completed dentition, closed base suture, and much wear
of the teeth are classified as ‘old.’ For the purpose of this
study, a suture is considered to be closed if at least threefourths of its entire extent have become obliterated on the
ectocranial surface.
In order to save space, particularly in the tables, the following abbreviations have been adopted in this paper: The
names of deciduous teeth begin with small letters and those
of permanent teeth with capital letters, thus avoiding endless
repetition of the words ‘deciduous’ and ‘permanent’ (except
a t the beginning of a sentence). In the dental formulae only
the initial letters of the names of particular teeth are given
and those of the upper jaw stand above the horizontal line,
whereas those of the lower jaw below this line. In the text
the names of the general types of teeth (e.g., Premolars) are
not abbreviated, but wherever the name of a specific tooth
(e.g., second Premolar) is mentioned it is abbreviated according to the following list:
Deeiduour 168th
medial incisor = il
lateral incisor = i2
canine = c
firat molar = m l
second molar = m2
Pmmanent taeth
medial Incisor = I1
lateral Incisor = I2
Canine = C
first Premolar = P1
second Premolar = P2
first Molar = M1
second Molar = M2
third Molar = Ed3
Appertaining to upper jaw = u.
Appertaining to lower jaw = 1.
Wild specimen = w.
Captive specimen = c.
496
ADOLPH H. SCHULTZ
AGE OF ERUPTION OF TEETH
Deciduous dentition
The ages of eruption of the deciduous teeth in primates
with known date of birth have been recorded in very few instances. As far as the author can ascertain, these ages are
unknown in all the lower primates, except the macaque and
one New World monkey. According to Scheff ( '13), the first
deciduous teeth of a rhesus monkey erupted on the thirtieth
day and according to Lashley and Watson ('13), in another
rhesus monkey, on the thirty-first day. Spiegel ( '29) reports
that in a female Pithecus irus the first teeth appeared on the
eighteenth day after birth and the last deciduous teeth on
the 142nd day. Quite recently, Spiegel ('34) has published
new data for the ages of eruption of the deciduous teeth in
twelve to thirteen Java macaques and h d s that the first dentition erupts on an average between the ages of 1.9 and 23.4
weeks, but can individually be as late as 3.6 weeks at its
beginning and as late as 40 weeks at its completion. According to the writer's ('33) data on ten to eighteen Pithecus
rhesus, born in captivity, the eruption of the deciduous teeth
occurs in this species on an average between the ages of 2.8
and 25.2 weeks, but varies individually to a very marked
extent.
It is very interesting to find that at least in one of the
platyrrhines these teeth appear at a much earlier age than
in any of the catarrhines for which we possess information.
According to English ( '34), the i l appeared in a captive-born
male night monkey (Aotus) on the second day and all deciduous teeth were present in the tenth week after birth.
There exists little more information regarding the actually
known age of eruption of the deciduous dentition of the higher
primates besides man. For the gibbon we possess only two
records: Robinson ('25) states that a Hylobates lar had only
four incisors at the known age of 6 weeks, and the author
( '33) found in a Hylobates leucogenys that the upper middle
and all four lower incisors have already erupted at the age
ERUPTION AND DECAY OF TEETH IN PRIMATES
497
of 29 days. If both these observations are taken into consideration and compared with the author’s data on macaques,
it can be tentatively stated that the first few deciduous teeth
of the gibbon appear only slightly later than those of the
macaque.
According to the excellent report by Brandes (’28) on an
orang-utan, born in captivity, the deciduous dentition of this
ape began to appear in the fifth month and was complete
a t the end of the first year of life. The author (’30) has
already reported that in another orang-utan only the eight
incisors and all the m l had erupted a t the known age of 1year.
Two other orang-utans of known age have been examined by
the writer at the Philadelphia Zoological Garden, a female
aged 18 months and a male aged 204 months. In both the
deciduous dentition was complete and no permanent teeth had
appeared as yet.
For the chimpanzee we possess one complete and two incomplete records on the eruption of the deciduous teeth in
animals of known date of birth. According to Jacobsen,
Jacobsen and Yoshioka (’32) the first milk teeth of the chimpanzee ‘Alpha’ appeared at the beginning of the third month
and the last at the beginning of the seventeenth month. The
chimpanzee ‘Julius ’ of the Philadelphia Zoological Garden
possessed only five incisors at the age of 6;)months (Schultz,
’30)’ a t which age ‘Alpha’ had already fourteen of her deciduous teeth. I n the chimpanzee ‘Aprilla’ of the Philadelphia
Zoological Garden‘ the first incisors (u. i l ) appeared at the
age of 34 months and all eight incisors were present in the
middle of the 6fth month. She was examined again at the
age of 22 months, when her deciduous dentition was seen to
be complete, and a t the age of 3 years and 8 months, it was
observed that all her first Molars were fully erupted.
For the gorilla there exist as yet no data on animals of
actually known age, since none have ever been born in captivity. Brandes (’30)’ basing his conclusions partly upon the
‘‘Aprilla’ was examined by the author on two occasions; other data were
obtained by a keeper and kindly sent to the writer by Dr. H. Fox.
498
ADOLPH H. SCHULTZ
observations by Reichenow on the age intervals between the
eruptions of the deciduous teeth in a captured gorilla infant,
estimates that the first teeth appear in the third month and
that all milk teeth are present at the age of 1year.
Judging by these meager facts, the period of eruption of
the deciduous dentition varies very considerably in all these
primates, but appears, in general, to start and to be completed
at earlier ages in the macaque and gibbon than in the three
large apes. Even in the latter this period begins earlier and
is much shorter than in man, in whom it extends approximately from the beginning of the seventh to the thirty-first
month.
Permanent dentition
Our knowledge of the ages of eruption of the permanent
teeth in primates of known age is unfortunately limited to
the macaque, the chimpanzee (appearance of Ml),and man.
I n addition, it has been possible to collect some observations
on the age intervals between the eruptions of different permanent teeth in a few of the higher primates besides man.
The data f o r the macaque are listed in table 2. Even these
few cases show conclusively that the ages at which the various
permanent teeth erupt can vary very considerably in different
individuals. The sequence of eruption, however, is comparatively stable, with the exception of the Premolars which follow
one another in particularly rapid succession. It is quite
evident that the average ages, as given in the table, can be
regarded as merely tentative values, but they are very much
preferable to the previously published estimates. There exists
apparently a long resting period before the eruption of the
last permanent teeth, the M3. These teeth had not yet appeared in an animal nearly 6+ years old and not in three
others more than 5 years old, but erupted in a fifth animal
during its seventh and eighth year. It is quite possible, of
course, that the last mentione’d ages may lie above the average
age of eruption, or may be typical for males only. The author
cannot agree, however, with the statement (as far as ‘erup-
W
(0
*
35
41
53
64
65
P
I
35
25
34
27
33
34
36
27
36
I1
12
0
P1
P2
-
UPPEU J A W
M1
M2
.__
40
i2
40
41
39
38
I2
m2
1112
46
56
P2
39
47
42
48
M2
1
?
41
21
43
19
39
-__.
9
7
4s
a1
2
8
21
20
20
23
M1
20
24
22
16
90
?
1
?
?
?
1
1
?
?
?
90
M3
I1
I2
0
I1
35
35
27
36
41
38
33
38
I2
ml
ml
45
49
P1
ml
ml
49
61
61
13
5
I
12
5
60
44
--
46
44
47
c
c
c
55
62
c
c
Pl
-
11
5
49
-
m2
m2
48
48
43
P2
59
m2
m2
48
P2
M1
M2
M3
38
46
41
51
M2
9
?
?
?
79
1
90
7
49
15
-
79
1
?
19
18
?
?
19
?
39
?
42
20
40
1
19
--9
7
1
24
20
18
22
M1
-- -- - -- -
LOWEU J A W
mmlceys ( P i t h e m rhesue) of known age
? = tooth has not yet appeared at maximum age observed.
ml
ml
42
48
42
P1
ml
ml
48
57
m2
m2
46
47
47
49
48
43
-5
5
5
47
68
48
9
14
10
c
c
c
55
65
c
c
- -- - --
37
38
0 ~-37
pecimens
9
8
Average age (months)
33
s9
Sequence
1 3
6
?
?
9
65'
72
97
76
73
B
J
H
42
47
65
76
106
6
6
6
6
6
G
X
-
___-
8EX
NO.
KAXIYUY
AOE
3BSEEVED
TABLE 2
The oge of eruption (in months) of the permanent teeth in them
500
ADOLPE H. SCHTJLTZ
tion’ is concerned) by Marshall (’33) that “Normally at five
years the eruption and calcification of the permanent teeth
is completed, . . . .” and doubts that this conclusion is based
upon observations on macaques of actually known, instead
of merely estimated, ages.
After this paper was written there appeared a report by
Spiegel (’34) containing valuable data on the ages of eruption of the permanent teeth in three to eleven Java macaques
(Pithecus irus). The approximate average ages of eruption
for this material are as follows (changed from Spiegel’s lunar
months into calendar months ; number of specimens in parentheses) : 1. M 1 = 19 months (ll), u. M 1 = 19 months (lo),
u. and 1. 11= 31 months (8), 1. I 2 =34 months (8), u. I 2 =
38 months (6),u. and 1. M2 =43 months (6),u. and 1. P1 and
P2 =52 months (5),u. and 1. C =53 months (4), 1. M3 =70
months (3), u. M3 =76 months (3). A comparison between
these data and those in table 2 shows the close agreement
between the corresponding results of Spiegel and those of
the writer. All the major points regarding the sequence of
eruption are identical and the average ages of eruption differ
in most cases by only 1 or 2 months, though the individual
values vary very considerably and both of the series are
extremely small for the higher ages. Three males among
Spiegel’s animals have reached an age at which the last permanent teeth are erupting, namely, 74, 76 and 78 months,
respectively. Even the highest of these ages lies 1 year below
the corresponding single record of the writer. This, however,
is not surprising, in view of the general rule that the higher
the average age of eruption of a tooth the greater are the
individual variations of this age.
According to the figures in table 2 as well as according to
the data of Spiegel, the Canines of the males erupt considerably later than those of the females.
The ages of eruption of the permanent teeth in chimpanzees
are listed in table 3. In none of these animals are the dates
of birth known. Their ages at the beginning of observation
can be estimated with a fairly high degree of accuracy on
g
c1
TABLE 3
72
Pan
I1
-
i2
i2
73
74
70
72
66
67
r.
r.
1.
71
6
70
70
69
71
C
74
74
90
89
M1
M1
M1
M1
78
83
36
36
36
36
36
36
33
33
91
91
76
80
78
76
84
84
m2
m2
m2
m2
ml
ml
ml
ml
93
93
-871
871
C
C
C
ml
ml
mS
m2
P2
78
78
85
87
73
73
1
1
P
I
1
1
M2
118
118
1
1
1
1
7
1
I
?
1
1
Y3
62
64
69
62
68
70
67
67
57
57
57
57
I1
90
92
95
95
99 1
95 1
C
C
C
C
C
C
-
0
--
65
66
69
68
73
73
70
70
62
i2
60
60
I2
LOW=
89
89
76
78
m2
m2
m2
m2
m2
m2
JAW
M1
M1
35
35
35
35
36
36
33
36
-
84
84
73
73
1
?
1
?
1
1
M2
104
-
104
126
126
1
1
1
1
1
7
1
1
M3
- -
- -
68
74
M1
74
79
80
74
M1
- - 7s
81
s5
77
7
11
1
8
SO
81
79
80
71
71
57
61
ml
ml
P1
- -
4
90
8S
78
56
79
118
6S
67
94
116
13
9
12
2
10
16
3
5
14
15
-- 1 (without accompanying figure)= tooth has not yet appeared at maximum age observed. The data for the Arst four chimpanzees
(except the ages of eruption of C in ‘Dwina’) have been calculated from the dates in the report by Bingham ( ’29).
66
66
66
r.
1.
133
nayton
Average age (months)
Sequence
68
68
r.
1.
126
1.
i2
i2
61
58
1.
C
C
r.
1.
il
il
i2
i2
21
UPPEE J A W
- -
0
I2
r.
- -
SIDE
Evo
98
62
Wendy
Dwina
60
MAXIMUM
AQE.
OBSERVED
Billy
NAYE
The age of eruption ( i n months) of the permanent teeth in chimpanaees (Pan spec. ?) of estimated age, but known age intervals
between eruption o/ different teeth
-
502
ADOLPH H. SCHULTZ
the basis of the following facts. Through the courtesy of
Prof. Robert M. Yerkes the writer was informed that, according to the observations by Doctors Yoshioka, Jacobsen and
Nissen of the Anthropoid Experiment Station of Yale University, the M1 appeared in three female chimpanzees with
known date of birth between the ages of 32 and 35 months
aud at 36 months all four M1 have erupted. According to
the records of Bingham ( ’29), on four living chimpanzees
(table 3), the eruption of the first I1 follows the appearance
of all M1 in 21 months in two of the animals and in 31 months
in the two others, i.e., on an average of 26 5 months.
The dates of eruption of the M1 have been recorded by
Bingham for all four of his chimpanzees. In the author’s
estimation of the ages of these animals, as used in table 3,
they are considered to have been 3 years old when all four
M1 had appeared. The two Hopkins chimpanzees (‘Evo’ and
‘Dayton’) were obtained when they already had their M1.
Their ages had to be estimated, therefore, as having equaled
approximately 62 months (all M1= 36 months first I1 =
26months) at the date of eruption of the first 11. Bingham’s
report was concluded when his oldest animal (‘Dwina’) had
reached the estimated age of 80 months. Through the kindness of Prof. Robert M. Yerkes, the author received Dwina’s
body after her death which occurred at the estimated age
of 98 months. At the latter age Dwina had as yet no M3
and of her Canines the upper two were fully erupted, but
the lower left was only partly out and the lower right had
barely reached the alveolar margin. The ‘probable ages’ of
eruption of Dwina’s Canines are given in table 3 accompanied
by question marks.
Judging by the fact that the upper M3 did not appear until
14 months after the lower M3 in Dayton, it may be assumed
that the upper M3 of Evo will not erupt until at least 1 year
after the appearance of her lower M3; i.e., not until she is
approximately 138 months old. This estimate is, furthermore,
+
503
ERUPTION AND DECAY OF TEETH I N PRIMATES
supported by the finding that in another female chimpanzee2
which cannot have been less than 11+and not more than
123 years old, the lower M3 are not yet fully erupted and the
upper M3 reach barely beyond the alveolar margin, though all
other permanent teeth are fully out. The following justifiable
estimates result in averages for the ages of eruption of the
M3 in chimpanzees which are somewhat higher than the corresponding figures in table 3 :
Cbimpanzss
Dayton
Evo
P. A. L. 128
Average age of eruption
1. ius
u. M8
104 months
126 months
approx. 126 months
118 months
approx. 138 months
approx. 138 months
119 m o n t h
131 months
Some further information regarding the ages of eruption
of the teeth in chimpanzees became available during the final
writing of this paper, when the author obtained the large
bodies of a male and of a female chimpanzee (Hopkins collection, nos. 391 and 392, not included in table 18) which he had
examined 6 years and 10 months before their death. At this
first examination both animals had their complete deciduous
dentitions, but as yet no M1. They were then, therefore, not
over 3 years of age but, judging by their size and by the
degree of attrition of their teeth, they were certainly over
2 years old. At the time of their death their ages must have
amounted to not less than 9 and not more than 10 years. At
this age both apes possess all their permanent teeth (the
Canines in even the male fully erupted), except the M3, of
which no trace can be seen in either jaw.
It is of interest to mention in this connection that the duration of time between the first appearance of a tooth and its
completed eruption differed very considerably in different
'The remains of this specimen (P. A. L. 128) were very generously given t o
the author by Prof. J. F. F'alton, who had received the animal from Mr. E.
Joseph, who states that he had obtained this chimpanzee originally 10) years
before ita death and that upon arrival it had been about 18 m o n t h old. As
experienced a man as Mi. Joseph would not likely have made a mistake i n his
original estimate, amounting t o more than 6 months. This ape reached, therefore,
a n age of 12 ( 26 months) years.
504
ADOLPH H. SCHULTZ
teeth of the two Hopkins chimpanzees. I n general, t h i s duration was shortest in the Premolars, only slightly longer in
the Incisors, and longest in the Canines. I n Evo the upper C
took nine months and the lower C 7 months for their full
eruption, whereas in Dayton these durations lasted approximately 3 months longer.
Since it is one of the purposes of this study to compare
t.he ages of eruption of the permanent teeth in man with the
corresponding ages in other primates, it is necessary to obtain
values for the ages of eruption in man which represent the
approximately average conditions of different races and of
the two sexes. Table 4 contains the data from the literature
which have been utilized for the calculation of such generalized averages. The first seven rows are based upon table 13
by Suk ( '19), omitting the column for Filipino boys as too
incomplete. The figures in table 4 are the arithmetic means
of the minimum and maximum ages listed by Suk. The two
question marks of Suk in his column for Czech boys have been
arbitrarily replaced by 240 ( ?) and 228 ( ?), respectively, in
order to introduce values for the ages of eruption of M3 in
whites. The eighth row is inserted for the same reason; it
represents a statement by Daffner ('02). The ninth row in
table 4 gives the averages of the preceding rows. Next follow
the averages of Rose's ('09, table 14) data. Since these are
based upon very much more extensive series than the data
of Bean and of Suk, and because they are real averages,
rather than means of ranges of variations, they are treated
as equivalent values to the averages in the ninth row. The
last averages in table 4, therefore, are the arithmetic means
of the preceding three rows only and are intended to show
the approximate average ages of eruption in man in general.
For quick, clear and complete comparisons between the data
presented so far, the drawings in figure 1 are most suitable.
The absolute ages of eruption in the three types of primates
are compared in the left part of the figure. It is seen that
the anthropoid ape is properly placed haif-way between the
representative of the lower Old World primates and man.
a
P
!4
F
4
8 g
$
i
F
E
Rase
Riiae
German
Daffner
21,139 European
19,882Europern
I
Average of above 3 row8
S a m in years and monthu
Elequence of eruption
I
Average of above
Zulu
ZllIU
American
American
German-American
German-American
Czech
Suk
Suk
andEluk
Bean
Bean
Bean
Matiegks
Bean
BACE
TABLE 4
d
0
SEX
90
90
108
102
102
96
102
I2
.126
120
138
126
138
132
136
a
126
114
126
120
132
120
126
P1
7-5
4
89
10s
8-7
6
107
92
89
102
--
M1
M2
11-0
10
1st
77
6-5
2
10-3
7
us
139
11-7
12
153
149
13A
138
156
150
150
150
156
12-6
14
160
--
79
78
66
78
78
66
78
78
78
125
136
121
-- 133
146
139
126
120
132
126
132
126
132
P2
..... . . .. . . ... -.....
-99
85
131
123
75
128
148
-- -- - --
66
78
90
90
90
90
90
It
-- -- - --
UPI'EB JAW
82
95
78
78
96
90
96
90
90
I2
134
126
114
138
120
138
126
126
135
126
114
132
120
138
126
132
P1
144
126
120
138
126
138
138
138
77
86
66
78
66
78
78
66
147
138
138
150
132
150
138
150
...
216
216
2461
2281
...
...
...
...
.. .. ... ... ---........
73 88
127
127
132 71 142 226
- - - - ----
66
66
78
66
78
78
78
11
--
LOWEB JAW
9-11
16
dS9
91
18.9
1so
1S8
6-6 7-7 10-8 10-10 11-6
8
3 5 9
11
-
78
74
145
886
6-2 11-11 18-10
1 . 13
15
... _-79 91 123 139 75 141
...
- 128 ----
...
239
228
228
258
2401
...
...
...
...
M3
--
Approximate average ages (in monthe) of the eruption of the permanent teeth in man
506
ADOLPH H. SCHULTZ
The beginning of the eruption of the permanent dentition
occurs in the macaque at the age of 1+ years, in the chimpanzee a t twice this age, i.e., at the end of the third year, and
in man at twice the latter age, namely, at 6 years. The completion of the permanent dentition, however, is accomplished
in the chimpanzee at an age which is relatively nearer to the
400
U. M
U.M
UM i
Fig.1 Diagrammatic representation of the absolute and the relative ages of
eruption of the teeth in macaque, chimpanzee and man, based upon the averages
in tables 2, 3 and 4.
corresponding age in the macaque than to that in man. It
is of particular interest to note that not only in man, but
also in the two other primates exists a very considerable
resting period before the eruption of the M3. A similar resting phase occurs after the eruption of the M1 in the macaque
and the chimpanzee, but not in man. These periods of rest
ERUPTION AND DECAY OF TEETH IN PRIMATES
507
during the process of eruption of the permanent dentition
are even more clearly apparent in the drawing on the right
of figure 1. In this drawing the age of eruption of the last
permanent teeth (u. M3) is assumed to represent what may
be termed ‘dental maturity’ and is shown to equal 100 on
the scale which starts with birth equal 0. On this scale of
relative ages the periods for the eruption of the deciduous
dentition differ comparatively little in man and chimpanzee.
The resting periods between the completion of the deciduous
and the commencement of the permanent dentitions are approximately the same in all three types of primates, amounting
to roughly 15 per cent of the ages between birth and dental
maturity. The Incisors appear at very similar relative ages
in man and in the macaque, but in the former they follow
immediately after the M1, which erupt comparatively late,
whereas in the latter there exists a striking period of inactivity
between the eruptions of M1 and of Incisors. The last mentioned resting phase is even more pronounced in the chimpanzee than in the macaque and, as will be shown later, seems
to be characteristic of all Old World primates, except man.
That this intermission in the process of eruption of the first
few permanent teeth exists also in the gorilla can be definitely
stated on the basis of the following observations which indicate in addition the duration of time between the completion
of the deciduous dentition and the first appearance of permanent teeth: The male lowland gorilla ‘Bamboo’ of the
Philadelphia Zoological Garden possessed only his incisors
and m l in August, 1927; Four months later, when weighing
17+ pounds, his deciduous dentition was completed. In
November, 1929, Bamboo had as yet no permanent teeth, but
all his M1 were seen to be fully out in June, 1930, and had
most likely started to appear in January of that year, or 25
months after the deciduous dentition was complete. Only
the upper and the lower I1 had been added to Bamboo’s
dentition in the middle of December, 1931, i.e., not until 23
months after the beginning eruption of his M1. The male
lowland gorilla ‘N’gi’ of the National Zoological Park had
508
ADOLPH H. SCHULTZ
gained his complete milk dentition early in 1928 (probably
in February). His M1 were found to have erupted (the lower
ones completely, the upper ones partly) in March, 1930, or,
as in Bamboo, 25 months after the completion of his milk
dentition. At the death of N’gi, in March, 1932, only the I1
of both jaws had been added to the permanent dentition, i.e.,
the resting period between the eruption of M1 and of I1 was
24 months, or practically the same as in the other gorilla,
and strikingly like this period in chimpanzees.
That there exists a resting stage between the eruption of
the M1 and that of the Incisors in Old World monkeys and
apes was recognized by Krogman ( ’30), who had examined
fairly extensive series of juvenile skulls of these primates
and has clearly indicated this resting stage in his table on
the sequence and rate of eruption of the teeth. This same
table, however, does not show the long resting period preceding the eruption of the M3 in the macaque and the chimpanzee.
I n man there is found a definite resting period between the
eruption of the Incisors and that of the subsequent permanent
teeth, a period which has no equivalent in chimpanzees and
in macaques. I n the latter two the M2 appear comparatively
early and the C relatively late, whereas in man the reversed
conditions form the rule. This is discussed more f d y in
the chapter on the sequence of eruption.
In this chapter it remains t o refer briefly to two recent
publications which contain statements in regard to the age
of eruption of the teeth in apes. Zuckerman (’28), after
repeated examinations on some chimpanzees of estimated
ages, concludes, that: “The available data indicate that the
durations of the chimpanzee tooth stages are practically the
same as in Man. The first permanent molar erupts between
five and six years, and the last molar at fifteen, or later.”
I t is evident from the data presented in this paper that the
writer cannot agree with the statement of Zuckerman which
must have resulted from erroneous age estimates and perhaps
have been influenced also by abnormally retarded eruptions
of certain teeth in one or more of his few captive animals.
ERUPTION AND DECAY OF TEETH IN PRIMATES
509
Without giving his evidence, Sir Arthur Keith ('31) has published a diagram showing the periods of eruption of the teeth
in anthropoid apes. I n this figure it appears that the permanent teeth of, e.g., the chimpanzee start to erupt in the
middle of the fifth year and have completely erupted not
until the end of the fourteenth year. These and many other
incorrect details justify the assumption that this comprehensive, but, unfortunately, premature diagram is based largely
upon estimates, rather than on observations on animals of
known age.
SEQUENCE O F ERUPTION O F PERMANENT TEETH
The following data appertaining to the sequence of eruption of the permanent teeth are based upon the study of dead
specimens of differing ages. For this study records were
made not only of each individual dental formula, but also
of the teeth which had not yet fully erupted a t the time of
death of the animal. I n each instance of incomplete eruption
of a tooth the degree of eruption was recorded as being approximately one-fourth, one-half or three-fourths complete.
Though these degrees had to be omitted in the final tables,
they have been given thorough consideration in arranging
the probable normal sequence of the different dental formulae
and in constructing the generalizing diagram in figure 2. If,
e.g., the upper M1 are only one-fourth erupted, whereas the
lower M 1 are three-fourths out, it is fully justifiable to assume
that the lower M1 had appeared before the upper ones. The
frequency distribution of the different dental formulae within
a large series of juvenile specimens permits conclusions in
regard to the rapidity with which certain teeth follow each
other. For instance, among 315 young macaques (table 15)
there are only 5 in which merely the upper P1 of the Premolars are present, and only 5 other specimens in which also
the upper P2 and lower P2 have erupted. This is a reliable
indication that the eruption of these Premolars takes place
in rapid succession, namely, at the ages of 47, 48 and 49
months, as shown by table 2. On the other hand, since there
510
ADOLPH H. SCHULTZ
are (in table 15) 69 macaques in which only all M1 have
appeared, it is safe to conclude that there must occur a very
marked resting period before the dental formula becomes
changed by the addition of further permanent teeth. The
correctness of this assumption can be verified by the data in
table 2, according to which this particular resting period
averages in macaques 11 months.
The tables of the dental formulae of dead material contain
a column for ‘exceptions’; i.e., unusual cases found only in
single specimens, which most likely do not represent the average sequence of eruption. The relative frequency of exceptions indicates the degree of variability of the sequence of
eruption in a particular primate genus, and any restriction
of all or most exceptions to certain ages tends to show which
phases of tooth eruption are most likely to proceed in irregular fashion.
Before discussing the findings regarding the sequence of
eruption of the permanent teeth in primates it would have
been desirable briefly to review this sequence in other mammalian groups, in order to be able to decide afterward whether
the particular modes of eruption in primates represent a general mammalian feature or are characteristic for only the
order of primates, or even only the suborder Simiae. Unfortunately, information on this subject is extremely scanty and
the author can merely contribute new data on one mammal
besides the primates. These data are collected in table 5 and
are the result of the writer’s examination of the dentitions
of twenty-six freshly killed dogs, in none of which all of the
permanent teeth had completely erupted. Based upon this
table the sequence of eruption of the permanent teeth of the
dog can very tentatively be given as follows: u. P1; 1. P1;
u. and 1. 11; 1. 12; u. 12; n. and 1. 13; 1. M1;u. M1; u. P4;
1. M2; 1. C; u. P 2 ; 1. P 2 ; u. C ; u. P3; u. M2; 1. P4;1. P 3 ; and
1. M3. As will be shown later, this sequence of eruption in
a carnivore differs very significantly from the sequence in
any of the primates studied. In contrast to the latter, in the
dog the P1 are the first permanent teeth to appear and these
511
ERUPTION AND DECAY OF TEETH I N PRIMATES
are followed by the Incisors and not until afterward are the
M1 added to the dentition.
According to the table given by Ellenberger and Baum
('15), the first and second Molars erupt before any other
permanent teeth in domesticated ungulates. These Molars
TABLE 5
Dental formuhe of twentysix dogs with at least purt o f the permanent deatition,
arranged to show the sequence of eruption of the teeth
(for abbreviations see chapter on Ezplanativns)
NUYBLB Or
SPECIMENS
1
I
DENTAL
Tommu
i i i c P1 m l m2 m3
iiic
mlm2m3
INCOYPLliTliLY
EEUPTID
u. P1
2
i i i e P 1 m l m2 m3
i i i c PI m l m2 m3
n. and 1. P1
1
I i i c P 1 m l m2 m3
I i i c P1 m l m2 m3
u. and 1. P1 and I1
1
I I i c P1 m l m2 m3
I I e P1 m l m2 m3
u. I2 and 1. P1
I I i e P1 PB m2 m3
IIicPl ..dm3
1
I I l c P1 m l m2 m3
I I1 c P l m l m2 m3 M1
u. and 1.13; 1. M1
1I I c P l m l m2 m3 M1
i i I e P1 m l m2 m3 M1
2
I I I c P1 m l m2 P 4 M1
I I I c P 1 m l m2 m3 M1 M2
u.and1.13; u.P4 11 I I e P1 m l m2 P 4 351
1. M2
I I I C p1 m l m2 m3 M1
1
I I I e P1 m l m2 P 4 M1
I I I C P l m l m2 m3 M1 M2
u. P1; 1. C; 1. M2
1
I I I c P1 P 2 m2 P 4 M1
I I1 C P1 P 2 m2 m3 M1 M2
u . m d l . P 2 ; 1.c;
1. M2
1
I1 I C P 1 P2 P 3 P4 M1 M2
I I I C P 1 m l m2 m3 M1 M2
1
I I I C P l P 2 P 3 P 4 M1 M2
/ I I I C PI m l P 3 P 4 M1 M2
u.andl.P3; u.M2
I
1. M3 (in all eases)
10
-
I I I C P 1 P 2 P 3 P 4 M1 M2
11I C P l P 2 P 3 P 4 M1 M2 M
1. M2; u. P 2 and
P3
..
I I I C m l P 3 P 4 MI. MO
I I I C P 1 P3P4MlM2
I
1
..
512
ADOLPH
E. SCHULTZ
are followed in cattle, e.g., by the I1 and 12, then by the P1
and P2, then by the M3 and P3, and finally by the I3 and 14.
That this order of eruption differs also from the typical
sequence of the appearance of teeth in primates will be evident from the discussion to follow.
NEW WORLD MONKEYS
The entire material of primate skulls which the author was
able to study contains only three specimens of marmosets
(Oedipomidas) in which not all of the permanent teeth had
fully erupted. It is impossible, therefore, to give more than
very fragmentary information regarding the sequence of
eruption in these primates, which are the only available representatives of the family Callithrichidae. The youngest of
these three specimens shows the following dental formula:
IIcmmmMM
I I c P m m M Y the lower P1 being only partly erupted. I n the
two older specimens all the permanent teeth are present, but
the upper C are only one-fourth out. As a tentative conclusion, it may be stated that in Oedipomidas all M2 appear
before any of the Premolars and that the Canines are the
last teeth to erupt completely.
I n the platyrrhine genus Saimiri (table 6) the M2 erupt
before any of the Incisors have appeared and the lower M3
erupt before any of the Premolars, though these statements
are based upon only single specimens and have to remain
very tentative until codrmed by observations on additional
material. As will be shown, these particular conditions represent exceptions among New World monkeys, but repeat what
forms the rule in langurs. The most probable, normal
sequence of eruption of the teeth of squirrel monkeys is shown
in figure 2. As in all other genera of the platyrrhine family
Cebidae, the Canines of Saimiri are considerably larger in
males than in females. Judging by the details regarding
incompletely erupted teeth (table 6), this secondary sex difference is not correlated with any clear sex difference in the
relative age or sequence of eruption of the Canines.
EBUPTION AMD DECAY OF TEETH IN PIUMATES
513
The platyrrhine genus Alouatta (table 7) shows some minor
peculiarities in the sequence of eruption of its permanent
teeth. As summarized in figure 2, the lower I1 are followed
not by the upper 11, as would be expected, but by the lower 12.
The upper I2 do not appear until the lower M2 have erupted.
In both sexes the upper C complete their eruption after that
TABLE 0
Dental formulae of twenty-three a p i w e l monkeys (Saimiri) with at least part of the
permanent dentition, arranged to shoru the sequence of eruption of the teeth
I
INCOMPLETELY LBUPTED
I
iicmmm
i i c m m m ~
L MI
iiemmmM
iicmmmM
u. M1
IiemmmMM
iicmmmMM
u. I1
IIemmmMM
LIcmmmMM
u. I2
IIcmmmM M
IIemmmMMM
L M3
3dand3Q
IIePPPMM
IIePPPMMM
In 4 caee8 u. P1 and in 2 of
these 1. P1
ldand2Q
IICPPPMM
IICPPPMMM
In 3 caeea u. and L C
5dand39
IICPPPMMY
IICPPPMMY
In 1 Q u. M3; in other 2 Q and
in 5 6 u. C; in 2 Q and 3 d
1
IcPPPMMM
d w.
IePPPMMM
(alwaye 1. C farther out)
1.
c
of the lower M3. I t is noteworthy that the three ‘exceptions’
are wild specimens and represent only minor variations, occurring during stages of growth characterized by rapid changes
in the dentition.
The capuchins represent probably the least specialized
genus of the platyrrhine subfamily Cebinae. Their sequence
of eruption is practically identical with that occurring in most
AYEOICAN JOUBNAL OW PHYSICAL ANTHBOP0U)QY. VOL. XIX, XO.
4
514
ADOLPH H. SCHULTZ
-M4-Mc 11
GORILLA - Mi
Ii
-7-
12
cn
I2
M4
12
Ii
11
M
2
M2
m
Pr Pf C
M2
I2
M2
P2
rt
C
Ms
M3
Ft
M4
b I2
MiC
Mi
PAN -:
M4
M3
M4
PON60 - M~
M4
HYLOBATES M4
Ii
14
14
I2
I2
I2
14
Mi
P4
M3
C
M3
C
M3
P2
M2
I2
M3
c
P2Yi
M2
M2
Ii I2
C
Mt-2
M2
PITHECUS 4
Mi
2 4
3
14 I2
M2
PC P2 C
M3
MC
PAPIO - M,
14 I2
M2 P4 R C
M3
M4
I4
I2
M2 R R
c
M3
LASIOPYGA
2 4
M
- T
M4
14
12
C Ma
CoLo6us - M~
h M2I2
P4 P2
Ms
NASALIS - Mi
I4 -ii-i% In5
ItM2
CZR P2
M2 Ir 12
M3
MI
C
Ii
Mi
M
Mj
S
Pz Pi c
PYGATHRIX h
M,
Ma
2 4
MC
ATELES- M~
M4
CEBUS --H4
-M2R R P3
CM3
f i R P3 C M3
M2 P4 Pz P3
c M 3
M2
P4 P2 P3 .c
M3
12 M2
Pi P2 P3
cM3
14 12
fi
I412
I4
I2
14 I2
M4
ALOUATTA M~
~
M4
SAIMIRI - M~
I1
4
I2
4
M2 14-2
M2
14 I2
fi
2
3
m
p
I
P2 P3 PI
.
3
cM3
SEQUENCE OF ERUPTION
Fig.2 Diagrammatic survey of the sequence of eruption of the permanent
teeth in m e r e n t genera of primates, based upon tables 4 and 6 to 19. Resting
periods are indicated by blank spaces between the symbols for successive teeth.
The thin horizontal lines above some of the letters indicate that the particular
upper and lower teeth underneath the line ean vary markedly i n their sequence of
eruption and this, usually, in connection with a rapid succession of eruption.
ERUPTION AND DECAY OF TEETH I N PRIMATES
515
TABLE 7
Dental formulae of seventy-k howlers (Abuatta) with at l m t part of the
permonen: dentition, arranged to show the sequence of w p t w n
of the permanent teeth
~
NUKE= OI
BPICIYENB
INCOYPLITELY EBUPFEI)
'INTu mBYULA
I
I
6
iiemmm
iiemmmM
3
iiemmmM
iicmmmM
In 3 cases u. M l
6
iicmmmM
IiemmmM
In 2 easea L I1
2
iiemmmM
IIemmmM
In 2 eaaea 1. I 2
3
/I
I I c m in m M M
em
IIem mm M
IIemmmMM
5
In 5 eaaea 1. M 1
111 3 eases 1. M2; in 2 cases u. I1
IIcmm mM M
IIemmmMM
7
IIemmmMM
II ePm m MM
In 7 esaes1.Pl; in 2 eaaeau. M2
5
IIePmmMM
IIcPm mMM
In 5 eases n. and 1. P1
1'
I
I II e P P P M M
In 4 cases u. M2 and in 1of thes
u.12
In 1 case u. P 2 and 1. P 3
2
IIePPmMM
In 2 eases 1. Cand u. and 1. P 2 ;
I I C P P m M M M in 1 ca8e 1. M3
2
I I C P P P M M In 2 eaaeau. Cand L M3; in 1
I I C P P m M M M caael. C
12
[icmmmhI
W.
LicmmmMM
In 3 eases u. 12 and in 2 of these
1.M2
7
2
LXCIRTIONII
(BINOLE OAeES)
I
I I C P P P M M In 11 cases u. C; in4 cases L C;
I I C P P P M M M in 2 eases 1. P 3
I I C P P P M M M I n 10 eaaeou. C; i n 5 easea u.
6gand5p I I C P P P M M M
M3:inleaaoI.P3
CI c P P PMM
C I e P m m M M"'
CIePmPMM
1I C P P P M MW.
516
ADOLPH H. SCHULTZ
the catarrhine genera. According to table 8 and as shown in
figure 2, the sequence of eruption of the teeth in Cebus is:
M l , I l , 12, M2, P1, P2, P3, C and N3. The order of appearTABLE
8
Dental formulae of flfty-one cupuchins (Cebus) with at leqst part of the permanent
dentition, arranged to show the sequence of eruption
of the permanent teeth
gsfi::
DENTAL FORMULA
I
INCOMPLETELY EgUPTED
iiemmm
iicmmmM
In 2 cases 1. M1
IiemmmM
IiemmmM
u. and 1. I1
l2
II emmmM
IIcmmmM
kn 5 emes u. I 2 and in 1 of
these u. M1
lo
IIemmmMM
IIemmmMM
In 3 c88es u. M2
IIemmmMM
IIcmmPMM
II e P P m M M
IIcPmmMM
IIemmmMM
ldanal?I I C P m m M M
2d
I IePYP M M
IIcPPPMM
2p
IICPPPMM
IICPPPMM
’
EXCEPTIONS
(SINQLX OASES)
I
/I
P3
u. P 2
In 2 cases 1. C and 1. P1
J.n lcaseu.
1. P1 a r c [ I e P P P M M
ps
In 2 cases P.and 1. C
[IemmmMMM
[ICPmmMM
mmM M M
[ 1 C.P
IICPPPM M
In 4 easee 1. M.7 nnd in 2 d
i I C a p P M M M of ,these u. C
CIcmPPMM
[ICPPPXMM
I I C P P P M M M In 7 cases u. M3;in 3 d
CIemPmMJdM
[IemmPMMM
dand 0 11 I c P. P P M M M
cases u. C
W.
ance of the Premolars can vary a good deal, the different
teeth most likely ernpting in rapid succession. All ‘exceptions’ belong to the phase of dental development after the
eruption of all M2. Only one of the four exceptions is a
ERUPTION AND DECAY OF TEETH I N PRIMATES
517
captive specimen, and this is a normal animal in every respect,
except that some of the deciduous molars have b.een retained
abnormally long-a condition which has caused also the three
exceptions in wild capuchins. Judging by the cases in table 8,
TABLE 9
Dental formulae of forty-two epider monkeys (Atelee) with at least part of the
permanent dentition, arranged to l o % the sequence of
emption of the pewnanent teeth
~~~~E~~
DENTAL MBYULA
INCOYPLETELY EPUPI%D
iiemmm
iiemmmM
In 3 cases 1. M1
iicmmmM
iiemmmM
I n 2 caaea u. and 1. M1
iiemmmM
IIemmmM
1. I1 and I3
IIemmmM
I I e m m m ~
In 1cage u. and 1. I 2
IIcmmmM
IIcmmmMM
In 2 eases 1. M2
IIePmmMM
IIcPmmMM
u. and 1. P1 and u. M2
2dand4p
IIePPPMM
IIePPPMM
In2caeeal.P2andP3;in
1casel.PT
2 dana 6 p
IIcPPPMM
IICPPPMM
[n 8 eases 1.
3
2d
1d a n d 5 0
3dandlO
C
EXOEPTION9
(9INOLE O U M )
IIePPPMM
IIemmPMM
w.
IIePPPMM
- w.
IIePPPMMM
g
IIePPPMM
In 2 case9 1. C and M3
IICPPPMMM
IICPPPMM
In 1 d a n d 19 u. C a n d L M
IICPPPMMM
IICPPPMMM
it seems highly probable that the Canines start and complete
their eruption slightly later in males than in females.
I n the last and most highly developed genus of New World
monkeys, Ateles (table 9 ) , the order of appearance of the
518
ADOLPH H. SCHULTZ
permanent teeth is practically the same as in Cebus. In the
former the upper C seem to erupt after the lower M3 and,
therefore, relatively late. The available material of Ateles
does,not permit a safe conclusion in regard to a possible sex
difference in the relative ages of eruption of the Canines,
such as has been demonstrated for Cebus. Again it is found
that the ‘exceptions’ are wild specimens, so that it can be
stated that among platyrrhines irregularities in the sequence
of eruption are not in any sense caused by conditions of
captivity, such as faulty diet or disease. That these exceptions do not represent by chanceqecies differences is proved
by the fact that the great majority of the specimens in table 9,
including the exceptions, are of the species Ateles geoffroyi.
In none of the primate genera studied has it been possible
to demonstrate species differences in the sequence of eruption.
It is conceivable, however, that a great deal of suitable additional material might reveal slightly different rules for the
order of appearance of some of the teeth in different species
of the same genus.
As far as the writer can ascertain, No11 (1866), Huxley
(1871) and Bolk ( ’26) are the only authors who have made
some previous statements ‘in regard to the sequence of eruption of the permanent teeth in platyrrhines. Noll, based upon
observations on the juvenile skulls of only one Cebus and
one Lagothrix, concludes correctly that in platyrrhines the
M1 appear first, t o be followed by the Incisors and immediately thereafter by the M2. Huxley merely mentions that in
Alouatta (=‘Mycetes’) and in Ateles the Canines usually
make their appearance before the M3, a statement which
agrees with the corresponding findings of the writer. Without recording the number of specimens examined, Bolk claims
that in Saimiri (=‘Chrysothrix’) and Cebus the teeth of the
lower jaw erupt in the following sequence: 11, 12, M1, M2,
P1, P2, P3, (all P simultaneously), C, M3, and adds that in
Ateles the Premolars erupt at the same time as the M2. Bolk
repeats clearly that, in contrast to catarrhines, in the platyrrhines the M1 do not appear until after all Incisors have
ERUPTION AND DECAY OF TEETH IN PRIMATES
519
erupted. How Bolk could have arrived at this particular
conclusion is a mystery, since it is not supported by a single
specimen among the 195 young platyrrhines examined by the
writer. Bolk’s claim is specially puzzling in regard to Saimiri,
because in this genus the Incisors do not appear until after
the eruption of even the M2. It may be mentioned in this
connection that this (quite evidently erroneous) h d i n g of
Incisors being followed by M l in platyrrhines, whereas by
&I2 in catarrhines, is regarded by Bolk as a remarkable support for his well-known hypothesis, according to which the
M1 of catarrhines are supposedly homologous to the m3 of
platyrrhines.
OLD WORLD MONKEYS
The Asiatic genus Pygathrix shows an extreme departure
from the general rule regarding the sequence of eruption of
the permanent teeth in primates. As is evident from table 10,
in the langurs all M2 erupt before any of the Incisors and
all &I3 before any of the Premolars and Canines. There are
some isolated exceptions to this generalization, but two of
these occur in captive specimens and in the single wild specimen, not conforming to this rule, only the upper M3 are
unusually late in appearance. On the basis of the data in
table 10, it seems probable that, in general, the Canines of
males erupt slightly later (or more slowly) than those of
females.
Bolk (’26) states that he had at his disposal a series of
successive stages representing the sequence of eruption of the
teeth in a langur and pictures eight specimens with incomplete
permanent dentition. According to this material the teeth of
Pygathrix aurata (=‘ Semnopithecus maurus’) erupt in the
following order: M1,11, 12, M2, P2, P1, C, M3. Again, this
finding of Bolk does not agree with the corresponding result
of the writer (fig. 2 and table 10). This discrepancy might
possibly be due to some species difference, though the writer’s
series of sixty-three young Pygathrix contains many different
species (but no P. aurata!) without showing different se-
520
ADOLPH H. SCHULTZ
quences of eruption ;or it might be explained in part by assuming that Bolk speaks only of the completed, rather than
started, eruption of the teeth. That Bolk generalizes without
giving consideration to the degrees of eruption is evident,
TABLE 10
Dental formzllae or eizty-three langura (Pygathriz) with at least part of the
permanent dentilion, arranged to show the sequence of
eruption of the permanent teeth
~
DENTAL
~ mBMULA
~
E
l4
1'
iicmmM
EXCEPTIONS
( S I N O W CASES)
INCOYPLLTELY
L
~
EPUPTID
~
/In 2 easeY n. M1
iiemmMM
iiemmMM
I n 2 cases u. M2
3
I
IiemmMM
In 2 easesn. 11
IiemmM
e.
IicmmM
3
IiemmMM
IlemmMM
[112~aWs1.12;in1~ase(e.)
u.M2
IiemmM
IIemm MM
a
I Iem mM
IIemmMM
In 3 eases u. 12
2
I Iem
In 2 eases u. I 2 and 1. M3
IIemmMMM
3
IIemmMMM
IIemmMM
W.
II
In 2 cases u. M3
lIemmMMM
'*
[I-mmMMM
1. C and P1
LICPPMMM
I1'
I
I I C P P MMM
I
p p M3f
~n 3 easeel. C; in 1 ease u. ~3
1 I e P P lv, hi M w * d
IICPPYMM
cp
[ICmPMMM
Iu. and 1. C andn. PI
I I C P P M M M I n 4 and 4 Pu. M3;in 13 6
and 3 9 u. C; in 3 3 1. C
IIC PPM MM
IICPPMM
I I C P PMMM
I
e.g., from the fact that in the text he claims that all I2 erupt
before the M2, but in his corresponding drawing (pl. .I,fig. 7)
the upper I2 are barely visible, whereas the upper and lower
M2 have nearly one-half erupted.
ERUPTION AND DECAY OF TEETH IN PRIMATES
521
For the second genus, Nasalis, of the subfamily Colobinae,
there are not enough young specimens available to study the
sequence of ‘eruption in more than an incomplete and tentative
manner. According to table 11 and the records on the degrees
of eruption, the lower M2 appear simultaneously with the
upper I 2 and the upper M2 follow immediately after the latter.
Again it is found that the Canines of males seem to erupt
somewhat later than those of females.
TABLE 11
Dental formulae of seven proboscis monkeys (Nosulk) with at lea& part of the
permanent dentition, arranged to show the sequence of eruption of the
permanent teeth. There are no ‘exceptions’
NUMBBE O F
SPPCIYINS
1
1
19
2Jand19
i
1
DENTAL FOEMULA
I
IXWOOMPLETLLY EBW-D
IIemmM
I I c m m If
c. I 2
IIemmMM
IIcmmMM
11.
and 1. I2 and u. M2
IIemmMM
IICmmMM
IIePPMM
IICPPMM
I rCPPMMM
IICPPMMM
ITnl O u . * n d I . M 3 ; i n ~ d u . a n d l . C
I n the genus Colobus (table 12) the M2 erupt immediately
before the I 2 of the corresponding jaw. This is of special
interest, because it permits the generalization that at least
the three genera Colobus, Nasalis and Pygathrix of the subfamily Colobinae have in common the tendency to have their
M2 erupt unusually early. This tendency is least pronounced
in Nasalis, in which the M2 follow immediately after the 12;
it is quite evident in Colobus, in which the M2 appear before
the 12; and it is most pronounced in Pygathrix, in which the
M2 precede even the I1 (fig. 2). The same tendency exists
also in Saimiri among the platyrrhines.
522
ADOLPH H. SCHULTZ
Selenka (1899), based upon his examination of only four
guereza skulls, has claimed the following order for the eruption of the teeth in Colobns: u. M1,l. M1, u. 11,l.11,u. 12,l. 12,
u. M2, 1. M2, u. C, 1. C.,u. P1,l. P1, u. P2, 1. P2, u. M3, 1. M3.
TABLE 12
Dental fornwlae of Pfteen guereaas (Colobus) with at least part of the permnent
dentition, arranged to 8how the 8eqvence of eruption of the
permanent teeth. There are no ‘ezceptions’
DENTAL M B Y U l d
INCOYPLLTELY LPUPTED
1
iicmm
iiemmM
4
iiemmM
iicmmM
1
IicmmM
IIcmmM
I2
1
IicmmMM
IicmmMM
.M2
1
IicmmMM
lIcmmMM
12 and u. MZ
1
IIcmmMM
IIcmmMM
.I2
2 5
IIcPPYM
IICPPMMM
n 2 cases 1. C and 1. M3
Id
IICPmMMM
IICPPMMM
P2
3d
IICPPMMM
IICPPMMM
n 3 cases u. and 1. C (1. C more out
than u. C)
M1
n 1 case u. M1
I n comparison with figure 2, it is readily seen that Selenka’s
data do not agree with the writer’s findings. There can be
no doubt, e.g., that Selenka is mistaken in his claim that all
the upper teeth erupt before the corresponding lower ones,
and it is d a c u l t to understand how such a definite conclusion
can possibly be reached from a study of only four specimens.
ERUPTION AND DECAY OF TEETH I N PRIMATES
523
The following three genera, representing the subfamily
Lasiopyginae, show practically identical sequences of eruption of their permanent teeth. This particular type of sequence is also found in the gibbons and the three large apes
and, with only insignificant alterations, in the platprrhine
capuchins and spider monkeys. I n all these primates the M1,
as the first permanent teeth, are followed by the 11, then by
the 12; after the Incisors appear the M2, to be followed in
varying order by the Premolars, afterward by the Canines,
and finally by the M3. The lower teeth erupt with few exceptions before the corresponding upper teeth. These rules are
clearly illustrated by the successive dental formulae of Lasiopyga (table 13). That there occurs a considerable resting
period between the eruption of the M1 and the I1 is indicated
by the fact that there are eighteen guenons with only all M1
out, whereas only two specimens showing the additional
eruption of the 11. I n a similar way it may be concluded
that in Lasiopyga, as in Pithecus (fig. l), there occurs a
second marked resting period before the eruption of the lower
M3 since all permanent teeth, except the M3, were found in
twenty-six guenons, the highest number of specimens with one
and. the same dental formula. A studymf .the data in table 13
reveals the fact that the Canines of males erupt relatively
later than those of females.
As mentioned above, Papio (table 14) shows practically the
same sequence of eruption of its teeth as does Lasiopyga.
There may exist a slight difference in the order of appearance
of the Premolars, but in view of the marked variability in
this particular sequence, which takes place in rapid succession, such a difference is still far from being definitely established. Again it can be stated that the Canines of the males
make their appearance slightly later than those of the females,
at least according to the data in table 14. The material in
this table contains thirty-four captive specimens, yet there are
only two ‘exceptions,’ only one of which being a captive speaimen and both representing only slight departures from the
usual sequence of eruption.
524
ADOLPH R. SCHULTZ
TABLE 13
Dental formdue of 100 guenone (Losiopyga) with at leaat part of the permanent
dentition, arranged to show the sequence of eruption
of the permanent teeth
NUYBEB OP
SPECIMENS
--
INCOYPmTtLY tPVPT6D
EXCEPTIONS
(SINOLE OASES)
4
iicmm
iicmmM
I n 4 cases 1. M1
18
iicmmM
iicmmM
In 3 cases u. M1
1
IiemmM
iiemmM
u. I1
1
IicmlnM
IicmmM
u. I1
1
IicmmM
IIcmmM
1. I2
5
IIemmM
IIcmmMM
I n 5 cases 1. M2; in 3 cases
11. I 2
6
IIcmmMM
IIcmmMM
I n 4 cases u. M2
2
tIcPmMM
IIcmmMM
In 2 cases u. P1; in 1case
u. M2
2
IIePPMM
CIcmPMM
In 2 cases u. P1, u. P2 and
1. P 2
IIcPPMM
IIcPmMM
2d
IIcP P MM
IIcPPMM
In 1case 1. P1
IIcmmMM
I ICPm M M "
iicmmM
IIcmmM
W.
'-
5dandlO
IIcPPMM
IICPPMM
I n 6 cases 1. C ; in 3 eases
9 dand 1 7 p
IICPPMM
IICPPMM
I n 9 6 and 119 u. C; in 9 8
1.C; in 2 91. P1
5dsnd79
IICPPMM
IICPPMMM
In4du.C;inl~l.Pl;in IICmmMM
10 cases 1. M3
I I C P P M M MW'?
8dandlP
IICPPMMM
IICPPMMM
In8du.C; in4Sand1?
1. P1
u. M3
IICPPMMM
I I C P P M M . w.?
525
ERUPTION AND DECAY OF TEETH I N PRIMATES
TABLE 14
Dental formulae of #fty-five baboons (Papio) with at least part of the permanent
dentition, awanged t o show the sequence of eruption
of the permanent teeth
INCOYPLETBLY EEUPTID
4
iiemm
iicmmM
In 4 c u e s 1. M1
13
iicmmM
iicmmM
tn 4 eases u. M1
1
iicmmM
IicmmM
1. I1
3
IiemmM
IicmmM
In 1 case u. 11; in 1ease 1. I1
5
IicmmM
LIcmmM
In 4 cases 1. I2 and 2 of these
eases u. I1
1
IIcmmM
1 1 c m m b1
11.
3
IIemmM
IIcmmMM
I n 3 eases 1. M2 ; in 1 case u. I2
3
IIemmMM
IIcmmMM
In 1ease n. and 1. M2
19
IIcmmMM
IICPmMM
u. M2; 1. C; 1. P1
19
IIcPmMM
IICPPMM
u. P1;1. C; 1. F1
IIcPPMM
IICPPMM
I n 1 S 1. C a n d l . PI
ldandl?
3 d and 6 9
IIICPPM
'1
3d
M
111C P P M M
I
IXCIPTIONS
(SINOLE OASES)
icmmM
:IemmM
C
I%
I n 3 d a n d 1 9 u . a n d l . C ; in
19u.Y2
IICPPMM
ICPP MM Y
I n 3 9 1. M3; i n ' l 8 u. and, 1. C
IICPPMMM
IICPPMMF
T% 3'cases u. M3 : in 1 case u. C
LICPmMM
L I C P m M M m"o
526
ADOLPH H. SCHULTZ
Huxley (1871)has stated that in baboons (=‘Cynomorpha’)
“the permanent canines make their appearance before, or,
at least, contemporaneously with, the hindermost molar in
both jaws.” The formula of Krogman (’30)for the sequence
of eruption of the permanent teeth in baboons agrees, in
general, very closely with the corresponding findings of the
writer, though Krogman did not recognize that, besides the
Incisors, also the Canines and Molars erupt in the lower jaw
slightly before the same teeth appear in the upper jaw.
For this study it was possible to examine a series of 315
skulls of young macaques3 (table 15), besides the living
macaques (table 2), so that the sequence of eruption of the
permanent teeth can be established more definitely for Pithecus than for any other genus of primates, besides man.
There can be no doubt that the first permanent teeth to
appear in macaques are the lower M1. They erupted before
the upper M1 in all the living specimens studied (the differences between the ages of eruption of the lower M 1 and the
upper M1 varying between 1 week and 2 months), and in
31 (17 14) of the skulls in table 15. No skulls were encountered showing indications of the upper M 1 having appeared before the lower M1. The second group of teeth to
be added to the permanent dentition are the medial Incisors.
The lower I1 appeared before the upper ones in 3 living
animals (table 2) and in 7 of the skulls (table 15, considering
also differing degrees of eruption). The reversed relation
existed in 4 living specimens and in 13 skulls. The upper
and lower I1 erupted simultaneously in 2 living macaques
and most likely in at least 16 of the skulls. The last condition
may be accepted as the general average for Pithecus and is
shown in this way in figure 2. Of the lateral Incisors the
lower ones precede the upper ones in the vast majority of
the cases (in 41 of the skulls, considering again the differing
degrees of eruption). In living macaques the lower I 2 erupt
+
‘The dental formulae of 200 of these young macaque skulls had already been
utilized and briefly diecussed by the author (’33) in his study on th- growth
and development of the macaque.
TABLE 16
Dental formulae of 315 macaques (Patheew) with at least part of the permanent
dentition, arranged to show the sequence of eruption o f the permanent teeth
INCOMPLETELY EBUPTED
17
69
6
3
22
17
20
23
iicmm
iicmmM
iicmmM
iicmmM
IicmmM
iicmmM
iicmmM
IicmmM
IicmmM
IicmmM
IicmmM
IIcmmM
IIcmmM
IIcmmM
IIcmmM
IIcmmMM
IIcmmMM
IT1c m m M M
IIcPmMM
4dand1P I I c m m M M
IIcPPMM
5d
IIcmPMM
19
IIcPmMM
4dand3Q L I C m m M M
IIcmmMM
IICPmMY
IIePPMM
4d&nd1Q I I C P Y M Y
"
LXCEPTIONS
(SINQW OASES)
Cn 11cases 1. M1
[n 14 eases u. M1
In 3 easea u. I1
In 3 eases 1. I1
In 11cases u. 11,in'5of these
cases 1. I1
In 1 3 caaes 1.12, in 3 of these
cases u. I1
I n 16 cases u. 12, in 7 of these
cases 1. I 2
I n 1 8 cases L M2, in 10 of thesc
cases u. 12, in 2 of these
cases 1. I 2
In 18 cases u. M2, in 4 of these
cases a I2
iicmmM
IIcmm M
'.
IicmmM
i I c m m M b a c.
IicmmM
W.
IIcmmMM
IIcmmMM
I I c m r n M M M w'
IIcPmMM
IIcPmMM
IIcmPMM
IIcmPMM
IIcPruYsL
I I C m P M M w*Q
'-
I n 5 eases u.p1
I n 4 e a s e s a P1; in 2 cases u.
P2;in2casesLP2
In 6 cases 1. C, in 5 of these
cases u.P1
I n 3 cases 1.C; in 2 cases 1. P1
I n 5 caws 1. C; in 1Q u. and 1. I I e P P M M
P1 and P 2
I I C m P M M w*
IICmmMM
In 2 cases n. c; in 1case u.
IICPmMM
2Q
I I c P P M M w-Q
IICPmMM
and 1. P1
In 15 d a n d 4 Q u. C, in 12 of
IICPPMM
l8dand 2 3 p I I C P P M M
these d 1. C
I I C P P M M - I n 3 d and 12 Q 1. M3; in 6 d I I C P m M M
and 17' I I C P P M M M
I I C P P M M M'.Q
11C P P M M M I n 1 3 cases u. M3, in 5 of these
cases 1.3f3: in 5 2 u. C
I I CP PM M M
I
bE7
"
528
ADOLPH
E. SCHULTZ
on an average 3 months before the upper ones (table 2) and,
according to Spiegel (’34, average of 6 specimens recalculated for calendar months), this difference is even 4 months.
The Incisors are very soon followed by the M2, the lower
ones appearing slightly before the upper ones (in 37 of the
skulls and in 5 of 7 living animals). In all the living macaques
and in all the skulls which permitted a decision in regard to
this problem the deciduous molars were not shed and the
replacing Premolars had not actually erupted until after the
M2 had appeared. It will be shown later that some authors
have claimed that the eruption of the Premolars precedes that
of the M2 - a conclusion for which the writer has f o m d no
evidence among his material which exceeds by far the series
utilized by other investigators. The writer has examined the
dentition in over 100 young macaques immediately after their
death and again when the skulls had been returned from
maceration, and thereby it was found that in many instances
some deciduous molars may be held merely by the gum and
one or two, partly resorbed, slender roots and might consequently very easily become lost after death, in which case
the Premolars underneath might erroneously be regarded as
erupting. The detailed order of appearance of the Premolars
varies a great deal, occupying on an average a period of only
3 months. It can be stated, however, that, as a rule, the upper
P1 erupt before any of the other .Premolars. The lower C
follow immediately after all the Premolars have appeared
and the upper C are added to the permanent dentition shortly
afterward. In ’some instances the upper and the lower C
can erupt simultaneously, but not a single case was encountered in which there was evidence that the upper C erupted
before the lower C. I n Pithecus, as in so many other primate
genera, the Canines of males erupt relatively later and somewhat more slowly than those of females (tables 2 and 15,
column ‘Incompletely erupted’). The last permanent teeth to
be added to the dentition of macaques are first the lower M3
and then the upper M3. That the former appear a considerable time before the latter is proved‘not only by the author’s
ERUPTION AND DECAY OF TEETH IN PRIMATES
529
records on a living animal of known age and by Spiegel’s
(’34) data on three other living macaques, but also by the
fact that in a total of twenty-seven skulls only the lower, but
not the upper M3 were out and that in eight additional skulls
the lower M3 had completely erupted at a time when the upper
M3 were only partly out. I n no skull was the reversed relation observed.
I t is interesting to note among the ‘exceptions’ two cases
in which the lower M2 had appeared before all of the Incisors
and two other specimens in which the lower M3 had erupted
before all the Premolars. These unusual cases resemble the
condition prevailing in the Colobinae.
Bolk (’26) was the first author to study the sequence of
eruption of the permanent teeth in macaques. Without stating
the number and distribution of specimens examined, he gives
the following formula for the order of appearance of the
teeth in the lower jaw of Pithecus irus (=‘Macams cynomolgus’): M1, 11, 12, M2, P2, P1, C, M3. This agrees exactly
with the corresponding findings of the author (fig. 2). In a
total material of sixty-three Pithecus rhesus, of which only an
unrecorded part were skulls with incomplete permanent dentition, Krogman (’30) studied the order of eruption of the
teeth, arriving a t the following conclusion : 1. M1, u. M1, - - u, 11, 1. 11, u. and 1. 12, -- u. P1,1. P1, u. P2, 1. P2, - 1. M2,
u. M2, - u. and 1. C, - u. and 1. M3 (- =resting period). The
most significant difference between this formula and the corresponding findings of the writer exists in the middle period
of dental eruption, for which Krogman states that the Premolars precede the M2 and that there even elapses some time
between the appearances of the former and of the latter teeth.
Krogman’s conclusion finds support in the following formula
for also Pithecus rhesus (=‘Macaca mulatta’), as stated by
Marshall ( ’33) : Ml, 11 and 12, P1 and P2 (twenty-third to
twenty-fourth month), M2 (twenty-eighth to twenty-ninth
month), C, M3. It is not quite clear, however, exactly what
Marshall meant by ‘eruption, and he mentions that “The
available data on animals between two and four years are
A X W C A X JOWNAL
OF PHYSICAL AXTHBOPOIl)QY, POL. XIS, NO. 4
530
ADOLPH H. SCHULTZ
somewhat fragmentary . . . .” The writer can merely repeat
that his seemingly ample evidence forces him to disagree with
the claims of the two last-mentioned authors that in macaques
the Premolars erupt before the M2. This discrepancy cannot
be explained as being due to some species difference, because
the large majority of the specimens in table 15 are also of
the species Pithecus rhesus. Furthermore, the recent investigations by Spiegel (’34) on living Pithecus irus have established the same sequence of eruption for this species as was
found by the writer for Pithecus rhesus (table 2). Spiegel
states specially that the Premolars do not appear until 1 to
12 months after the eruption of the M2.
HIGHER PRIMATES
The sequence’of eruption of the permanent teeth of gibbons
(table 16) is practically the same as in the subfamily Lasiopyginae. The upper and lower I1 erupt simultaneously in
most cases. All other teeth seem to appear, as a rule, slightly
sooner in the lower than in the upper jaw. The Canines
erupt before the M3 and somewhat earlier in females than
in males. The latter difference is particularly noteworthy,
in view of the fact that in Hylobates the Canines are of practically the same large size in both sexes.
Huxley (1871) mentions that “ I n the Gibbons, the permanent canine emerges contemporaneously with, or before, the
last molar.’’ Based upon his study of fifteen young skulls
of Hylobates concolor, Kirchner (1895) gives the following
sequence of eruption: 1. 11, u. 11, 1. M1, u. M1, 1. 12, u. 12,
1. M2, u. M2, u. P1,l. P1, u. P2, 1. P2,l. C, u. C, 1. M3, u. M3.
The small number of cases examined may explain the erroneous conclusion of Kirchner that the I1 are the first permanent
teeth to appear. With the exception of this reversed relation
in the order of appearance of the I1 and the M1, and the
claim that the upper Premolars appear before the lower ones,
Kirchner’s formula agrees very well with the author’s findings (fig. 2). The latter are in general agreement with the
following formula for Hylobates (and Symphalangus !) given
ERUPTION AND DECAY OF TEETH I N PRIMATES
531
-
by Krogman ( '30): u. and 1. M1, -- 1.11, u. 11,u. and 1. 12,
u. M2,l. M2, - u. and 1. P1, u. and 1. P2, -- u. and 1. C, u. and
1. M3. This formula differs from the writer's results merely
TABLE 16
Dental formulae of forty gibbona (Hylobates) with at least part of the permanent
dentition, arranged t o show the sequence of eruption
of the permanent teeth
NUYBEB Or
SPICIYENS
DENTAL M B Y U L A
INCOMPLETELY m U P T E D
1
.iemm
.iemmM
1
iiemmM
iiemmM
1
[icmmM
iicmmM
4
IiemmM
liemmM
I n 3 cases u. and 1. I1
6
IiemmM
LlemmM
I n 1 m e 1. I 2
4
IIemml
IlemmY
I n 4 cases ILI 2
1
IIcmmM
[IcmmMM
1. M2
3
IIemmMM
IIePmMM
In 3 c a m 1. P1
2d
IIcPPMM
IIePPMM
I n 1 case u. P2
30
IIcPPMM
IICPPMM
I n 2 saseg 1. C
2 dand 1 5
IICPPMM
IICPPMM
In 1 dand 10 u. C
ldand35
IICPPMM
I n 1 0 u. C; in 1 d u. and 1. C, i x
IICPPMMM
both these eases 1. M3
4Jand25
I I C P P M M M In 6 eases u. C; in 2 d and 2 Q
IICPPMMM
u. M3
EXCEPTIONS
( S I N Q W OAeES)
1. M 1
IcPPMM
Ic P P M M M
.
'
532
ADOLPH H. SCHULTZ
in regard to the relations between corresponding teeth in the
two jaws and in regard to the occurrence and relative duration
of the time intervals.
The orang-utan (table 17) shows essentially the same order
of appearance of the permanent teeth as the gibbon. Of the
two (wild) ‘exceptions’ the first is of interest because, as in
so many other exceptions, it demonstrates a tendency to retain
some deciduous teeth for an abnormally long period. The
second case is probably not a real exception at all, but shows
that in some females the upper and lower C can erupt before
all Premolars have appeared.
Owen (1840 to 1845) and Nagitot (1869) are probably the
first authors who have attempted to study the sequence of
eruption of the teeth in anthropoid apes. The former author,
after examining some skulls of young orang-utans, gives the
following sequence of eruption for the teeth of this ape:
M1, 11, M2, 12, P1 and P2, M3, C. He states specifically
that (apparently in a living animal) the lower I 2 erupt 8
months after the upper M2. This, however, must be a very
exceptional and probably abnormal occurrence. Magitot bases
his conclusions upon an examination of the juvenile skulls
of 3 orang-utans, 3 chimpanzees and 6 gorillas. Of this total
of 12 specimens 7 possessed only the M1, whereas 3 had all
permanent teeth, though not all completely erupted. This
leaves only two specimens for the entire period, covering the
eruption of all Incisors, M2, all Premolars and Canines! I t
is not surprising, therefore, that later and better substantiated investigations did not support most of Magitot’s conclusions in regard to the order of appearance of the permanent
teeth in the large apes in general. This order he states to be
‘‘absolument dans le m6me ordre que chez l’homme, c’est;-dire :” - M1, - I1 and 12, P1 and P2, C, - M2, - M3 - (- =
terminating Magitot’s ‘periods of dental development’) .
Huxley (1871) mentions that in the large apes, in contrast
to the gibbons, “the last permanent canine is cut, ordinarily,
only after the appearance of the last molar.” This statement, too, is not in agreement with the findings of later
authors.
ERUPTION AND DECAY OF TEETH I N PBIMATES
533
On a very considerable series (the total number of available
specimens is not recorded) of young orangutan skulls Selenka
(1898) has studied the sequence of eruption of the teeth.
According to his tabulated data, the M1 are always the first
permanent teeth to appear, to be followed by the lower I1
TABLE 17
Dental formulae of twenty-eight orang-utans (Pongo) with at leaat port of the
permanent dentition, arrolrged to 8 h w the sequence of
eruption of the permanent teeth
INCOMPLETELY EBUPTED
'I
13 and 2 9
4'Md
"11
iicmm
iicmmM
Iu 1 ease 1. Ml
iiemmM
iicmmM
In 1 case u. M1
IicmmM
IicmmM
In 2 w
IIemmMM
IIcmmMM
In 2 eases u. M2 ;in 1 case u. I2
IIcPmMM
IIcPPMM
1. P1
IIcPPMM
IIePPMM
In 1 case 1. P1
IICPPMM
I CP P M M
In 3 'and 1 9u. and 1. C
I1
iicmm MM
C I c m P M M w'
CICPPMM
I: I C P m M M w'p
IICPPMM
In 2 enses u. C; in 1 case 1. M3
IICPPMMM
2g
l'
s u. and 1.
I
IICPPMMM
u. and 1. C
IICPPMMM
in five cases and by the upper M2 in six other cases. The
detailed order of appearance of the different Incisors and
the upper and lower M2 Selenka found to vary a great deal,
so that in quite a number of skulls the upper and (or) lower
M2 seemed to have actually erupted before all the Incisors
had appeared. This constitutes the chief discrepancy be-
534
ADOLPH H. SCHULTZ
tween the results of Selenka on one side and those of Krogman, Keil and of the writer on the other. The appearance of
all M1, Incisors and M2 is followed in all of Selenka’s cases-by
the Premolars and Canines, the latter erupting in the great
majority of the cases after the former. The M3 are recorded
as the last normal teeth to erupt in all but one instance, in
which the lower C had been delayed in their usual order of
appearance. Selenka mentions also that supernumerary
Molars erupt always after the usual permanent dentition has
been completed. He distinguishes different phases in the
process of eruption which are separated by intermissions of
varying duration. The first of these intermissions follows
the eruption of the M1, the second that of the Incisors and
M2, and the third that of the Canines. Between the last two
intermissions occur the third and the fourth phases of eruption which are described as follows (in free translation):
“Third phuse. After a considerable intermission appear the
anterior and posterior Premolars, in varying order, but in
rapid succession. Fourth phuse. The Canines are added
immediately, but they grow extraordinarily slowly in males.’’
According to the findings of Krogman and those of the writer,
there exists no significant period of inactivity preceding the
eruption of the Premolars, i.e., at the time for which Selenka
claims his second intermission.
Krogman (’30), who has studied a total of 134 orang-utan
skulls (again it is impossible to find out in how many of these
the permanent dentition is as yet incomplete), gives the following formula for the sequence of eruption of the teeth:
u. and 1. M1, --- 1.11, u. I1,l. 12, u. 12, - u. and 1. M2, u. and 1.
P1, u. and 1. P2, -- u. and 1. C, - u. and 1. M3 (- =relative
time interval). This formula agrees in nearly all essential
points with the corresponding results of the wfiter (fig. 2), the
only and as such minor differences exist in regard to the detailed order of appearance of the Premolars and of some of
the same teeth in the upper and in the lower jaw.
Recently Keil ( ’33) has re-examined the Selenka collection
of orang-utan skulls ( sixty-five young specimens), obtaining
535
ERUPTION AND DECAY OF TEETH I N PRIMATES
TABLE 18
Dental formulae or eighty-aiz chimpawees (Pan) with part or the permanent
dentition, arranged to show the . 9 e & ~ ~ eof eruption
of the permanent teeth
INOOMPLETILY EEUPTID
LSOEPFIONS
( SINQm OASES)
2
iicmm
iiemmM
33
iicmmM
iicmmM
2
IicmmM
IicmmM
In 2 case8 u. 11; in 1case 1. I1
3
IicmmM
IIcmmM
I n 1case u. 11;in 1 m e L I 2
2
IIcmmM
IIcmmM
I n 1case u. I 2
2
IIcmmM
IIcmmMM
In 2 cases 1. M2
iicmmM
iicmmMM
5
I I c in m M M
IIcmmMM
I n 2 cases u. M2
t-I-c P m M
IIc-PM
1
IIcmmMM
IIcPmMM
1. P1 and u. M2
11-PPY
c. P
11--PMM
2
IIcPmMM
IIcmPMM
I n 1case u. P1 and 1. P2
IIcmmMM
IIcPPMM
2
IIcPPMM
I I e I? ni M M
In 1case u. P1 and u. P 2
IIcPPMM
IIcPPYM
In 1case u. and 1. P1; in 1case
u. P 2
IIcPPMM
IICPPMM
I n 2 cases 1. C, in 1 0 u. P1
IICPPMM
IIcPPMM
In 2 ages u. C
IICPPMM
IICPPMM
In 1dand 3 ?u. and 1. C;in
29 u. c
IICPPMM
1 I C P '1 M M M
I n 1d a n d 1Pu. and]. Cand
1.M3
In 1m e 1. M1
In 6 cases u. M1, in 2 of these
1. M 1
C.
C.
IV'
536
DOLPH H. SCHTJLTZ
the following formula for the sequence of eruption of the
permanent teeth: M 1 - - I1 I2 M2 -- (P1 P2) - C -- M3.
This formula agrees with the corresponding conclusions of
Krogman and of the writer with the exception of the resting
period after the eruption of the M2.
The sequence of eruption of the permanent teeth of the
chimpanzee (table 18) is, as a rule, practically the same as
that of the orang-utan. I n captive specimens, however, there
can occur a signillcant difference, consisting in the eruption
of some of the Premolars earlier than some of the M2 (table 3
and ‘exceptions’ in table 18). Such an order of appearance
of these particular teeth has not been observed by the writer
in any wild chimpanzee and does not occur in all of the captive specimens. It seems that some consequences of captivity
(rickets?) can in chimpanzees produce the occasional delay
in the eruption of M2 or, possibly, an abnormally early shedding of molars, thereby facilitating an earlier appearance of
the replacing Premolars.
The long resting period in dental eruption, following after
the appearance of the M1, is unmistakably indicated by the
fact that in thirty-five of the eighty-six chimpanzees with
incomplete dentitions the M1 are the only permanent teeth
present. This resting period has actually been found to last
considerably over 2 years (table 3). It is to be expected that
a dental formula, remaining unchanged for such a long time,
should be encountered in a much higher percentage of specimens than the formulae which undergo alterations in comparatively rapid succession. A sex difference in the relative time
of eruption of the Canines, existing in many other primate
genera, is not clearly defined in the author’s material of
chimpanzees.
Selenka (1899) gives in form of a diagram the following
sequence of eruption of the permanent teeth of chimpanzee
(only three skulls!) : u. M1, 1. M1, 1. 11, u. 11, 1. M2, u. 12,
1. 12, u. M2, 1. P1, u. P1, 1. P2, u. P2, u. C, 1. C, u. M3, 1. M3.
I n two other skulls he found that the last six types of teeth
appeared in the following, slightly different order: u. P2,
EBUPTION AND DECAY OF TEETH I N PRIMATES
537
1. P2,l. C, u. C, 1. M3, u. M3. This agrees in most the major
points with the corresponding results of the writer, the only
essential difference consists in the early eruption of the lower
M2 according to Selenka - a condition found by the writer
in only one captive specimen and hence listed as an exception.
Based upon his study of a series of twenty-seven chimpanzee
skulls with incompletely erupted permanent dentitions, Zuckerman ('28) concludes that the usual order of appearance of
the teeth is as follows: M1, 11, 12, M2, P1, P2, C, M3. This
is in complete accord with the corresponding results of the
writer (fig. 2). This particular sequence is furthermore supported in its major points by the report of Krogman ('30),
who has studied a very considerable, though unnaxqed, number of young chimpanzee skulls, and summarizes his findings
in the following formula: u. and 1. M1, --- u. and 1. 11,u. 12,
1. 12, u. and 1. M2, u. P2, 1. P2, u. and 1. P1, -- 1. C, u. C, u. and 1. M3 (- =relative time interval).
The order of appearance of the permanent teeth of gorillas
(table 19) is the same as that in the other large apes, except
in the detailed sequence of eruption of the Premolars which
has been found to be particularly .variable in all the primate
genera investigated. Among the gorilla skulls examined there
are thirteen in which the M2 are either at least incompletely
erupted before any Premolar has appeared, or else they are
completely out before the Premolars, which have appeared,
have completed their eruption. I n not a single skull has the
reversed relation been observed. This is specially mentioned,
because Krogman has claimed that in the gorilla the M2 do
not erupt until some time after all the Premolars have appeared. The data on the degrees of eruption support the
conclusion that in the gorilla the large Canines of the males
erupt slightly later and much more slowly than the small
Canines of the females.
Selenka (1899)' gives two diagrams for the order of appearance of the teeth of gorilla. The first, based upon only four
skulls, shows the following sequence :u. M1,l. M1, u. M2,l. M2,
u. 11, 1. 11, u. 12, 1. 12, 1. P1, u. P1, 1. P2, u. P2, u. c, 1. c,
-
538
ADOLPH H. SCHULTZ
TABLE ID
Dental formulue of seventy-eight gorillas (Gorilla) with part of the permanent
dentition. arranged to show the sequence of eruption
of the permanent teeth
INCOYPLITSLY SPUPTED
EXCEPTIONS
(S110QW CASES)
6
iicmm
iicmmM
I n 6 casea 1. M1
14
iicmmM
iicmmM
I n 1 case u. MI
3
iicmmM
IicmmM
I n 2 casee 1. I1
3
I i c in m M
11i c m m M
In 1 case u. I1
1
IiemmM
l'IemmM
u. I1 and 1. I 2
2
ITemmM
IIcmmM
I n 1case u. I 2
1
IIcmmM
LIcmmMM
1. M2
5
I Iem'm M M
IIcmmMM
In 2 cases n. M2
2
IIcmPMM
IIcmmMM
In 2 cases u. P 2
1
IIcPmMM
IIcmPMM
u. P1 and 1. P 2
3
IIcPPMM
11 I c m P M M
I n 1case u. P1; in 2 eases
u. and 1. PO
11-PmMM
11-PPMM
28and59
IIcPPMM
IIcPPMM
I n 3 cases 1. P1
IIcPPMM
11C P P M M M
11-PPNM
IICPPMM
In 2 cases 1. C; in 1 ease u. P2
IICPPMM
I I c P P M M **'
IICPPMM
IICPPMM
I n 2 d a n d 1On. and 1. C
IICPPMM
IICPPMMM
I n 12 cases 1. M3 ;i n 6 6 u.
and 1. c
29
2dand69
6 d and 7 91
I-cmmM
W.
iicmmM
IIcmmMM
I I c P m M M w*
IICPPMMM
IICPPMM
lv-
0
ERUPTION A N D DECAY OF TEETH IN PRIMATES
539
1. M3, u. M3. The second and incomplete diagram, composed
of the dentitions of only three additional specimens, gives the
following sequence: 1) u. M1, 2) 1. M1, 3 ) u. 11, 4) 1. M2,
5) u. M2,6) 1.11, . . . . 13) 1. C, 14) u. C, 15) u. M3,16) 1. M3.
One wonders whether Selenka regarded an M2 as ‘erupting’
when merely visible in the depth of its open alveolus, or
whether he has had to estimate the relative order of eruption
of the M2, since his far too small series may have lacked
the necessary stages showing the actual, normal order of
appearance of these particula’r teeth. It is interesting to note
that Selenka considers the M2 the second (upper and lower)
teeth to appear, whereas the writer assigns them to the fourth
place and Krogman even to the sixth!
Virchow ( ’20) mentions that in the gorilla (two specimens)
the M2 erupt before the Premolars. Krogman’s (’30) formula
for the sequence and rate of eruption of the teeth of
gorilla, derived from his examination of a very considerable material (actual number of skulls unrecorded), is here
transcribed as follows: u. and 1. M1, --- u. and 1.11, u. and 1.
12, - u. and 1. P2,l. P1, u. P1, - u. and 1. M2, -- 1. C, u. C, ‘or’
u. and 1. M3. As mentioned above, the writer is forced t o
disagree with this formula chiefly in regard to the order of
eruption of the M2, and also in regard t o the reversal in
the order of first appearance of the Canines and the M3.
That the M3 may erupt simultaneously with, or even slightly
earlier than the Canines is admitted as a possibility for an
exceptional caae (table 19, ‘Exceptions’), but never as a sufficiently frequent occurrence to constitute a tppical condition.
The sequence of eruption of the permanent teeth of man,
as shown diagrammatically in figure 2, is based upon the data
assembled in table 4, which represent a general average condition for the recent races of the genus Homo. As in nearly
all the other primates, in man the permanent dentition starts
with the eruption of the M l and is completed with the appearance of the M3, but the middle order of eruption differs from
that of all other primates in several very significant respecfs.
The Incisors follow the appearance of the M1 without any
540
ADOLPH H. SCHULTZ
resting period, the Premolars and Canines erupt early, and
the M2 unusually late. According to table 4, the average ages
of eruption of the lower I1 are in many instances the same
as the average ages of eruption of the upper M1. It is to be
expected, therefore, that individually the former teeth can
frequently appear even somewhat earlier than the latter teeth,
and such a relation does, indeed, constitute another unique
condition among all primates.
PHYLOGENETIC CHANGES I N SEQUENCE O F ERUPTION O F TEETH
I n view of the extreme scarcity of information in regard
to the sequence of eruption of the teeth in mammals besides
the primates and the complete lack of data for the suborder
of prosimians, it is as yet impossible to decide which general
type of sequence represents a primitive and original condition
and which other types must in consequence be regarded as
phplogenetic specializations. As a mere working hypothesis,
however, it may be assumed that the most primitive sequence
of eruption consists in an initial simple addition of teeth
( M l , M2 and M3) of the second generation to those of the
first generation and only subsequently in a replacement of
deciduous teeth by permanent ones, and this beginning with
the I1 and 12, followed by the various Premolars, and ended
with the Canines. With advancing specializations of the primates appeared a trend toward marked prolongation of the
period of individual growth, so that the deciduous teeth
would have had to function for steadily increasing periods
if their replacement had not gradually become shifted to progressively earlier places in the entire order of appearance
of the permanent tee’th. If this hypothesis is tentatively
accepted as plausible and as not contradicted by known facts,
the formulae assembled in figure 2 can be interpreted in the
following manner (fig. 3) : All the primates investigated have
retained at least a part of .the hypothetical, original sequence
of eruption of the permanent teeth, this part consisting in
the initial addition of the M1. Saimiri and Pygathrix adhere
still further to the primitive formula by adding next the M2.
541
ERUPTION AND DECAY OF TEETH IN PRIMATES
I n the other genera this second step has become delayed by
the accelerated beginning of the replacement of deciduous
teeth which, however, starts in the assumed original order,
i.e., with the 11, followed immediately by the I2 (except in
Colobus in which the M2 follow the 11). After this newly
acquired, early appearance of the Incisors there occurs a
return to the primitive condition of adding, rather than replacing, teeth in all the primates, except man. I n Pygathrix
all M3 are being added, in Saimiri at least the lower M3, and
HYPOTHETICAL
ORIGINAL FORMULA
PY6ATHR'Xs
SAlMlRl
(L.JAW)
y' y2
A,
A 2
4
COLOBUS
MI ?IM*
c
HOMO
$
M< >I2
Tp
14Gh
iP
4
It
PP
/
;5
5
i2
F M y
l
o
-
4
/I2
P C P M2
SEQUENCE OF ERUPTION
M4 14
c' I -
h +I
Fig.3 Condensed and generalized representation of the different degrees of
evolutionary change in the sequence of eruption of the permanent teeth in primates. The unaltered order of appearance of a tooth is indicated by a perpendicular arrow, a shifting in this order by a diagonal arrow.
in the other monkeys and apes all the M2. I n man alone has
the original order of eruption become even more specialized
at this point, inasmuch as the addition of the M2 is postponed until the deciduous molars and canines have been replaced. The primitive, rapid addition of the M3 has become
relatively retarded in all primates, but decidedly less so in
Pygathrix and (regarding the lower M3) in Saimiri than in
any of the other genera. This is due to the comparatively
early replacement of the molars and canines. The order in
the latter replacement follows in all monkeys and apes in
general the primitive formula, i.e., the Premolars appear
542
ADOLPH H. SCHULTZ
before the Canines. In man, on the other hand, even this
sequence has become changed, inasmuch as particularly the
lower Canines erupt frequently before all Premolars have
appeared.
These considerations lead to the hypothetical and general
conclusion that the sequence of eruption of the permanent
teeth is most primitive in Saimiri among the platyrrhines
and in Pygathrix among the catarrhines and that it is most
specialized among all primates in the recent representatives
of the genus Homo. I t is of great significance in this connection that, according to Virchow ( 'ZO), in the fossil child
of Ehringsdarf the M2 erupt before the P1 and P2, and not
afterward as in modern man.' The human specializations
consist in the rapid succession in eruption of the M1 and 11,
in the complete replacement of the deciduous dentition before
the M2 are being added to the permanent dentition, and in
the appearance of the lower C before at least the P2. I n
other words, it is unquestionably a new and exclusive aquisition of man that his M2 erupt comparatively late and his
Premolars and, particularly, Canines relatively early. I t is
perhaps more than a striking coincidence that this comparatively 'premature' appearance of the Canines of man is associated with a relative size of these teeth which is so markedly
smaller than in any other primates of at least the male sex.
These conditions are shown diagrammatically in figure 3,
where it is seen that any shifting in the order of appearance
of the teeth which are being added to the dentition (Molars)
proceeds from left to right, whereas all shifting in the general
sequence of eruption of the teeth which replace the deciduous
dentition takes place in the opposite direction, i.e., from right
to left. Figure 3 shows also very clearly that in man alone
becomes the deciduous dentition completely replaced by permanent teeth before the M2 are being added to the dental
arches. I n the large majority of the primates the process
of replacement is interrupted, instead of followed, by the
'Spiegel ('34) has recently called attention to the fact that the picture by
GorjanoviE-Kramberger ('06) of the fossil human mandible ' C ' from Krapina
ehowa an erupted M2 alongside an m2 (and not a P2).
ERUPTION AND DECAY OF TEETH IN PRIMATES
543
addition of M2. I n conclusion it must be emphasized that
in regard to these conditions the large apes fall into one group
with the majority of the monkeys and are sharply separated
from man. This is not the place for following the temptation
to speculate on the possible tames and consequences of this
highly specialized sequence of eruption of the teeth of man.
It may be pointed out, however, that in man the tremendous
and unique lengthening of the duration of postnatal growth,
accompanied by corresponding increases in the ages of dental
eruption, has brought about a dangerously long period of
functioning for the deciduous teeth without any improvement
in the durability of the substance of these teeth. If the completed replacement of the deciduous dentition had to wait
in man, as in other primates, until after the addition of the
M2, the life span of some of the milk teeth would have to be
lengthened by several years, even though this span is on an
average already more than twice as long in man as, e.g., in
the macaque.
CORRELATIONS BETWEEN ERUPTION AND ATTRITION OF TEETH
AND CLOSURE OF SOME CRANIAL SUTURES
As mentioned in. the chapter on Explanations, for each
skull the state of attrition of the teeth and the ectocranial
closure of two of the sutures has been recordecl and this,
chiefly, for the purpose of classifying the material according
to age.
I n the first age group, containing all specimens with incompletely erupted permanent dentition, noteworthy attrition of
the teeth is rare. In skulls still lacking the M3 one can observe occasionally a slight degree of wear on the M1 and the
I1 and in a few cases even on the I 2 and the C. Such premature attrition of teeth among ‘young’ specimens occurs
somewhat more frequently in the large apes and the gibbons
than in the lower primates. Among the latter it has been
observed in a total of only six cases in the entire material
of ‘young’ platyrrhines.
544
ADOLPH IT. SCHULTZ
As a rule, the base suture and the sagittal suture are
(at least partly) open during the entire period of dental
eruption. The following exceptions to this rule have been
noted in the material listed in tables 6 to 19, and referring
invariably to specimens from the last two rows of these
tables, i.e., to the very oldest specimens with incompletely
erupted dentitions :
Gmus
Gorilla
Hylobates
Pithecns
Colobns
XpccimsM with dosed
Bore ruture
8agittal ruturd
2
4
0
5
3
2
0
2
After the completed eruption of the entire permanent dentition, the attrition of the teeth becomes rapidly more noticeable
with advancing age, beginning generally on the teeth with
comparatively early ages of eruption, i.e., the M1 and the
Incisors, though the Canines are also among the first teeth
to show marked signs of wear in a considerable percentage
of the cases. I n practically all primates the M2 become worn
only after attrition is clearly recognizable on the M1, Incisors
and Canines, but before it is seen on the Premolars and the
343. In many old specimens it is observed that the Incisors
and Canines have become reduced to mere stumps, the crowns
of these teeth having nearly or entirely disappeared, and yet
the M3 and at least some of the Premolars show but a moderate degree of attrition. I n even more extreme cases all teeth
can be worn to the gums. Such extremes have been found
with surprising frequency among the higher primates, they
are slightly less common among lower catarrhines, and they
did not occur among any of the platyrrhines examined, except
in the genus Ateles.
The percentage distribution of the degrees of dental attrition and of the closure of cranial sutures in primates with
completely erupted dentitions is shown in table 20. The data
in this table are of manifold interest, but will be discussed
very briefly and without considering the sequence of suture
545
ERUPTION AND DECAY OF TEETH IN PRIMATES
closure or the literature on the latter problem.6 In contrast
to the lower primates, the higher forms contain generally
very few specimens in which both the base suture and the
sagittal suture are still open after all the permanent teeth
TABLE ao
The correlations between the degree of attrition of the teeth and the closure of two of
the cranial sutures in specimens with oompletely erupted permanent dentition.
The pgures represent the percentages of specintau showing particular
colnbinutions in these conditions
Open
QINUS
TOTAL
IUYBEB
OP
IXULLS
Gorilla
245
Pan
126
67
Pongo
130
Hylobates
227
Pithecua
68
Papio
134
Lasiopyga
59
Colobus
41‘
Nasalis
273
Pygathrix
158
Ateles
105
Cebus
Alouatta
210
Saimiri
48
OcdiDomidar
35
Mean
I (1926) I
ClOSed
Open
Ilight
-
Jlight Mu&
Bdult
Adult Adull
4
12
6
2
25
22
62
31
51
26
32
45
19
69
11
28
--
..
..
..
..
6
..
5
..
2
2
1
1
-18
34
9
1
7
7
..
3
5
14
0.4
..
3
..
5
3
..
..
7
5
.. ..
.. ..
.. 1 ..
.. .. ..
..
1
slight
..
6 1 2
0.8
11
..
6
7
2
7
27
’
BASE SUTUBB
Clmd
Much
..
2
..
..
Blight
Much
Adult
Old
3R
39
36
32
49
30
44
10
9
27
32
3
8
35
-37
25
42
7
19
2
25
13
3
14
5
3
5
5
2
14
37
27
12
33
1
2
13
30
17
14
3
11
72
-15
8
16
..
BAQITTAL SUTlJm
--
..
..
D=QBP= or ATTRITION O r TIPTH
AQE
..
3
21
have completely erupted. Only 2 per cent of the gibbons,
4 per cent of the gorillas, 6 per cent of the orang-utans, and
12 per cent of the chimpanzees have both the sutures still
open. In none of these specimens do the teeth show ‘much’
61t must be emphasized that, as stated under ‘Explanations,’ a suture is here
considered to be closed only when at least three-foiirths of its length have become
entirely obliterated. The selection of this definition for the present purpose may
in part explain certain apparent discrepancies between the results of the writer
and those of hrogman (’30), who has studied in great detail the suture closure
in anthropoids, macaques and baboons.
546
ADOLPH H. SCHULTZ
wear. I n lower primates, on the other hand, ‘much’ wear
does occur, though rarely, among the high numbers of adults
with both sutures still open. Even if the sagittal suture is
already closed, ‘much’ wear is found but rarely as long as
the base suture is still open, namely, on an average in only
2 per cent of the specimens. The orang-utan stands out among
all the genera examined as the primate with by far the highest
percentage (37) of cases showing the combination of closed
sagittal and open base suture and as the only primate in
which the reversed combination could not be observed. I n
Oedipomidas, on the other hand, not a single specimen showed
the former combination, whereas the latter was encountered
in 83 per cent of the cases. With the exception of Alouatta,
platyrrhines are characterized by the very late, and hence
rare, closure of the sagittal suture. The gibbons are distinguished by having the highest percentage (91) of adult
and old specimens with both sutures closed; gorillas (77)
and chimpanzees (73) rank next in this respect, to be followed
by Alouatta (65), Papio (63), and Pongo (57). I n the remaining genera these percentages are much smaller, reaching their
lowest values in Ateles (3) and in Saimiri (0).
Even after both sutures have become closed, the teeth are
not or only ‘slightly’ worn in mostly very considerable percentages of the cases of nearly all the genera. It is, however,
the group of skulls with obliteration of both sutures which
shows on an average the highest percentage (24) of cases
with ‘much’ wear of the teeth. This average percentage of
cases showing ‘much’ wear decreases to 8 if only the base
suture is closed, and to 1 if neither of these sutures has as
yet become obliterated.
DEVIATIONS FROM THE NORMAL CONDITIONS OF THE PERMANENT
DENTITION
I n the course of the examination of the permanent dentitions of primates a very considerable number of records
accumulated, showing the frequency with which different
variations in size, number and position of certain teeth occur
ERUPTIOX AND DECAY OF TEETH IN PRIMATES
.. .. .. ..
2
: :$
9 m
or(
- k
*rl
.. .. .. .. .. ..
AYPRICAN JOURNAL Olr PHYSICAIA ANTHROPOLOGY, VOL. XIS, NO.
.. .. .. ..
4
547
548
ADOLPH H. SCHULTZ
in the various genera. Special attention was also paid to
crowded and impacted teeth and to abnormally long retained
deciduous teeth. The percentage frequencies of these deviations from the normal conditions are listed in table 21.
Striking reductions in size are found chiefly in the 113, but
occur also, though very rarely, in other teeth. Thus, the upper
I2 are vestigial in one gorilla6 and in one Oedipomidas; in
one macaque a rudimentary Canine was encountered and in
one gibbon and one baboon a P1 is clearly of diminutive size.
Abnormally small M3 with reductions in the number of cusps
Fig.4 Upper jaw of Alouatta palliata
left M3.
0
w. (A. S. 777)' showing vestigial
and of roots are quite common among gibbons, as has already
been convincingly demonstrated by a number of investigators
(Schultz, '33). I n all other catarrhines (besides man and
gibbon) rudimentary M3 are extremely rare, having been
found in only one chimpanzee and one macaque. In platyrrhines, 011 the other hand, striking rediictions in the size of
the M3 (fig. 4) occur in all genera, manifesting a general
trend toward the elimination of these teeth, an elimination
which has already been accomplished in Oedipomidas and all
other Callithrichidae. The most extreme reduction in size,
i.e., the complete absence of one or more M3, is also very
This specimen has been pictured in another paper by the author ( '32, fig. 1).
Rudimentary upper I2 in another gorilla are mentioned by Regnault (1893).
EIlUPTION AND DECAY OF T E E T H I N PRIMATES
549
rare in lower catarrhines, fairly rare in the large apes (only
in 3 chimpanzees and in 1 orang-utan?), but quite frequent
in gibbons. Among the latter &I3are missing in 5 out of 130
specimens examined by the aut,hor and in 2 out of 68 specinlens
(adult Hylobates concolor) examined by Kirchner (1899). I n
the New World genera Ateless and Cebus the congenital lack
of M3 is much more frequent than in any other primate genus,
except Homo. I n man one or more M3 are undeveloped in
as much as 19 per cent of the cases (de Terra, ' l l ) , though
some recent studies have resulted in smaller frequencies ; e.g.,
Fig. 5 Upper jaw of adult &bus unicolor
tal lack of both M3.
9 c. (P. A. L. S l ) , showing congeni-
according to Goblirsch ('30), one or more h13 were seen to
be lacking on roentgenograms of 2112 adult white patients
in 9 per cent of the cases. In extreme cases, as shown for
instance in figure 5, even the M2 of platyrrhines may bear
signs of marked reduction. That the complete suppression
of M3 is a hereditary character in man has been demonstrated
'Bateson (1691) has reported the congenital lack of the upper r. M3 in an
orang-utan and Briihl (quoted by Zuckerkandl, 1896) nientions another orang-utan
skull with the complete absence of both upper M3.
Buteson (1894) records the congenital lack of M3 in 3 out of 60 Ateles skulls.
He did not encounter any such cases among the adult skulls of 66 Cebus and of
81 Alouatta. A series of pictures, showing different variations regarding the
reduction in size of the M3 in Ateles and in Cebus have been published by the
author ('25) i n a former paper.
550
ADOLPH H. SCHULTZ
by a pedigree published by the author ('34). That it is of
a hereditary nature also in monkeys, appears probable, in
view of the fact that in the species Ateles geoffroyi the M3
were found to be congenitally lacking in 3.5 per cent of the
author's series from Chiriqui, Panama, whereas in 15.4 per
cent of the specimens collected in one locality in eastern
Nicaragua.
The addition of fourth Molars, o r the manifestation of an
increased developmental activity at the aboral ends of the
dental laminae, occurs with surprising frequency in the large
apes, but is rare in man, gibboiis, and most lower primates.
I n the series studied by the author one or more M4 were
observed in 14 gorillas (138 and 1 9 ; 12 times upper and
2 times lower jaw; in 7 cases bilateral and in 7 cases nnilateral occurrence), 4 chimpanzees (18 and 3 0 ; 2 times upper
and 2 times lower jaw; in 2 cases bilateral and in 2 cases
unilateral occurrence) and 4 orang-utans (48 ; 1 time upper,
2 times lower, and 1 time upper and lower jaw; in the last
case also lower r. M5;9 in 2 jaws bilateral and in 3 jaws
unilateral occurrence). In the large series of 194 adult orangutan skulls of Selenka (1898), M4 are present in 19.6 per
cent of the cases ( 8 25 per cent,lo P 15 per cent). According
to the latter author (1899),M4 occur in gorillas in about 8
per cent of all cases, whereas in chimpanzees they have not
been observed in his extensive experience. I n man M 4 are
encountered sporadically and probably in no race more frequently than in aboriginal Australians among whom they have
been found in 1.5 per cent of the cases (Campbell, '25). I n
contrast to the large apes, the gibbons show M4 extremely
rarely, only one such case having been observed by the author
in a series of 130 specimens. Kirchner (1895)reports another
case in a Hylobates concolor, encountered in a series of 68
' A picture and brief description of this extreme case has been given h a
paper by HrdliEka ( '07). Additional cases of M4 in skulls of the three large apes
have been listed by Bateson (1894).
'"Duckworth ('15) makes the incredible assertion:
in the orang-iitan
the frequency of occurrence (of M4) in the male sex amounts to nearly 50 per
cent
. This statement is based on the examination of the very large collection
(i.e., the Selenka collection).
(more than 200 crania) at Munich
". . . .
...
. . . ."
ERUPTION AND DECAY OF TEETH IN PRIMATES
551
adult, gibbons. Bateson (1894) did not find M.4 in a material
of 51 gibbons. By combining these three series, it can be
stated that M4 are found among 249 gibbons in only 2 instances, or in 0.8 per cent of the cases.
I n the lower primates well-developed M4 are present in
only 2 macaques, 1 guereza, and 2 spider monkeys (fig. 6).
Bateson (1894) records supernumerary Molars in a baboon
and a macaque among 419 Old World monkeys examined,
and in 2 capuchins, 3 spider monkeys, and 1 howler among
284 (or more?) New World monkeys of the family Cebidae.
Though the writer did not encounter M 4 in any Papio, Shaw
(’27) found these teeth in 3.6 per cent of 112 south African
baboons (probably P. porcarius).
Fig. 6 Lower jaw of Ateles geoffroyi
M4 on both sides.
9 w.
(A. S. 1005), showing well-developed
The real congenital lack of upper I 2 was observed in only
2 specimens, a gorilla and a gibbon. In man this lack occurs
in over 2 per cent of whites (Schultz, ’34) and is a hereditary
character. The congenital absence of lower 11, on the other
hand, is rare in man, but fairly common among apes and
monkeys (table 21). It is particularly frequent in howlers,
among which it is found in 7 Alouatta palliata” and in 1
One of the cases is i l h t r a t e d in another paper by the author ( ’25, fig. 16).
I t may be mentioned here that Ruffer (’20) has stated: “Absence of the first
left mandibular incisor must have been fairly common in Lower Egypt, as four
such cases have been observed in ancient Alexandria skulls.”
552
ADOLPH H. SCHULTZ
A. villosa (5 8 and 3 0 ; 5 times left 11, 1 time right 11, and
2 times both I1 lacking without leaving any diastema).
Congenitally missing Premolars were not encountered
among the higher primates, but occurred in catarrhine as
well as platyrrhine monkeys in a total of 7 cases. I n all
these cases the lack is unilateral, in 5 cases a P1 is missing,
and in the remaining 2 cases a P2. Invariably there is no
space between the adjoining teeth in place of the missing
Premolar, as demonstrated, e.g., by figure 20 in the author's
('25) former paper on this subject. Supernumerary Premolars were observed in the entire material in only 2 cases,
a howler and a chimpanzee, both of which possess an additional, well-formed Premolar on one side of the lower jaw.
Bateson (1894) has recorded the occurrence of supernumerary
Premolars in a Brachyteles, an Ateles, and an Alouatta, and
Wegner ('08) has described this anomaly in a Symphalangus.
The only other numerical variations in teeth among the
specimens examined 'by the author are the following cases:
Additional Incisor in upper jaw in one gorilla, in lower jaw
in another gorilla, an orang-utan, and a squirrel monkey.
Incomplete twinning of tooth, i.e., doubling of crown, of upper
I 2 in a guereza and of lower I1 in a howler. Apparently
congenital lack of one Canine (with I 2 touching P1) in a
macaque and in a capuchin. Cases of supernumerary Incisors
in monkeys and apes have also been reported by Bateson
(1894) and by Wegner ( '09).
Positional variations of the permanent teeth of primates
have been studied in great detail on a very large material
by Colyer ('19 and '31). It suffices here, therefore, to give
the author's corresponding observations merely in the condensed form of percentage frequencies with which the two
most common positional variations were met with (table 21)
and to discuss these very briefly. The percentages of specimens with one or more Incisors protruding strikingly beyond
the others on account of crowding of the Incisors are listed
in two of the columns in table 21. Two such cases are shown
by excellent photographs in the figures 160 and 161 of the
ERUPTION AND DECAY OF TEETH IN PRIMATES
553
book by Colyer ('31). A slight, though quite evident, degree
of crowding among the Incisors, such as is shown in the lower
jaw of a chimpanzee in figure 8, is surprisingly common in
most genera and has not been included among the cases listed
in table 21. A high degree of crowding, leading to marked
and abnormal protrusion of one or several Incisors, is generally more frequent in the upper than in the lower jaw. It
Fig. 7 Upper jaw of young Ateles geoffroyi
ing of right Y3.
Fig. 8 Lom?er jaw of young chimpanzee
of right P2.
9
2
w. (A. S. 975), showing crowd-
c. (P. A. L. 112), showing crowding
554
ADOLPH H. SCHULTZ
affects the I1 much more commonly than the 12. Such crowding of Incisors is particularly frequent in the langurs, among
which it occurred (in the upper jaw) in fifteen specimens, belonging to five different species.
Marked crowding, accompanied by displacement, of Premolars is not at all a rare finding among wild or captive apes
and monkeys. Figure 7 illustrates a moderate degree of this
abnormal condition. Crowding in the Premolar region with-
F i g . 9 Upper jaw of Papio hamadryas
of right P2.
d w.
(A. 5. l68), showing twisting
out pushing a tooth out of its proper alignment, but with
wedging the tooth between its neighbors, thus keeping it from
full eruption, was encountered only in two captive chimpanzees of which one is shown in figure 8, in one captive macaque,
and in one wild capuchin. The first mentioned type of crowding of Premolars is, on an average, three times more frequent
in the upper than in the lower jaw. I n the 48 specimens in
which an upper Premolar had been crowded out of its proper
place it had been pushed lingually 41 times, whereas labially
only 7 times. On the other hand, in the 13 specimens with
ERUPTION AND DECAY OF TEETH IN PRIMATES
555
crowding of lower Premolars the displacement occurred lingually 2 times and labially 11 times. The crowding affected
the P1 in 29 per cent, the P2 in 56 per cent, and the P3 in
15 per cent of the cases with crowded Premolars. In 27 of
the 61 specimens with crowded Premolars the corresponding
teeth on the right and the left side of the jaw were pushed
out of place, in 2 other specimens a P1 and a P2 on only one
side of the jaw showed the crowding, and in the remaining
32 specimens only one of all the Premolars was affected.
In four skulls of Alouatta palliata the bilateral, lingual
displacement of upper P1 is very clearly caused by the ab-
Fig. 10 Upper jaw of old Ateles geoffroyi d w. (A. S. 1009), showing impacted
left C (and fully erupted, partly worn, right C).
normal retention of the m l ; one of these cases is illustrated
in figure 11 of a former paper by the author ('25). I n the
majority of the cases of displaced Premolars, however, the
abnormal position appears to be caused directly by a disproportion, no matter how slight, between the size of the jaw
and that of the dentition. In a number of other instances a
displaced Premolar is also markedly twisted, thus occupying
more space sagittally than if standing in a normal direction.
A moderate rotation of, chiefly, P2, as shown, for instance,
in figure 9, is quite common among apes and monkeys-a fact
which has been convincingly demonstrated by Colyer ('31).
This frequent condition of rotation is, however, not necessarily
556
ADOLPH H. SCHULTZ
correlated with the much rarer occurrence of actual displacement of Premolars.
It remains in this chapter to discuss very briefly the frequencies with which impacted permanent teeth and retained
deciduous teeth have been found among apes and monkeys
(table 21). Impacted teeth were encountered in a total of
24 adult or old specimens (22 w.+ 2 c.). I n only 1 instance
was an Incisor impacted, in 6 cases a Canine (fig. lo), in 7
cases a Premolar (in 2 instances due to the abnormal retention of the corresponding molar), in 5 cases an M3, and in
the remaining 5 cases one or two b14. The chimpanzees show
the highest frequency (5.6 per cent) of cases with impacted
Fig. 11 Lower jaw of Pithecua rhema
(and worn) right i l and lack of 11.
0
e. ( A . S. 1168), showing retained
teeth, but in man such cases are even more common. According to a recent study by Mead ( '30), on a total of 6389 roentgenograms and skulls of different- human races, impacted
teeth are found in man, on a general average, in 7.9 per cent
of the cases (whites alone =12.7 per cent), but of all impactions in man 94 per cent appertain to M3 and only 6 per cent
to all the other teeth together.
Retained deciduous teeth in fully adult apes and monkeys
are rarer than impacted teeth. The former occurred among
platyrrhines only in the genus Alouatta, 4 adult, wild specimens having failed to shed their upper ml, and 1 specimen
its upper il. Among catarrhines deciduous teeth were retained abnormally long in 13 specimens (table 21), of which
ERUPTION AND DECAY OF TEETH I N PRIMATES
557
only 3 are captives. I n the entire group of these cases a total
of 12 incisors (i
i l 5 i2), 3 canines, arid 16 molars (‘7 m l
9 m2) was retained, 19 of these teeth belonging to the upper
jaw and the remaining 12 to the lower jaw. I n the case of
10 (7 i, 1c, 2 m2) of these retained deciduous teeth (belonging
to 7 specimens), the corresponding permanent teeth were congenitally lacking. One such instance is shown in figure 11.
I n 5 cases (2 c 3 m2) of retained deciduous teeth, the permanent teeth, which should have replaced them, were impacted. The 7 abnormally long retained m l and 1 of the
retained m2 caused the corresponding Premolars to be pushed
out of their normal position.
The data presented in this chapter furnish abundant proof
for the general conclusion that congenital and developmental
irregularities in the dentition are f a r from being restricted
to man, occurring with varying and at times very considerable
frequency among apes and Old as well as New World monkeys
and this in captive and in wild specimens.
+
+
+
DESTRUCTION O F THE TEETH AND OF THE ALVEOLI AND LOSS
O F TEETH
The previous chapters have dealt chiefly with the beginning
and middle periods in the life of the teeth of primates and
have described the eruption, attrition, and developmental
irregularities of the teeth. This final chapter is devoted to
the problems of the decay and loss of teeth and of the destruction and dosure of alveoli. The chief emphasis is here
placed not on the details of the dental pathology, but on the
relative prevalence of the more or less extensive breaking
down of the dental apparatus in the various groups of primates.
F o r every skull examined was recorded the occurrence of
dental caries, of manifestations of alveolar abscess, and of
the complete loss of one or more teeth, followed by the disappearance of the corresponding alveoli. A tooth is here
called ‘carious,’ if it contains a more or less extensive and
irregular cavity, caused by the progressive destruction of
558
ADOLPH H. SCHULTZ
Fig. 12 Lower jaw of Pithecus rhesus
cavity in left M1.
e. (P. A. L. 78), showing carious
Fig.13 Lower jaw of young Papio sphinx c. ( A . S. l65), showing caries in
both M1.
ERUPTION AND DECAY OF TEETH I N PRIMATES
559
dental tissue. As a rule, caries in primates is readily distinguished from the effect of localized attrition and of erosion.
In some instances, however, in which bhe crown of a tooth
(mostly Molars) had apparently broken during the life of
Fig.14
Lower jaw of Cebus capucinus
9 w. (A. S. 858), showing caries in
both M1.
Fig. 13 Upper jaw of young Pithecua rhesus
in both 11.
9 c. (A. S. 1164), showing caries
its owner, it seemed doubtful whether this happened in coilsequence of a previously existing carious cavity or was exclusively due to some other cause, such as traumatic injury.
N o such uncertain case was included among the records on
560
ADOLPH H. SCHVLTZ
caries. Examples of carious cavities in the dentitions of
monkeys are shown by the figures 12 to 17. Many other
excellent pictures have been published by Colyer ( ’31), who
has discussed caries in primates in great detail without, however, considering the age changes in the frequency of caries.
As ‘abscess’ was recorded every clear incidence in which
any visible part of the alveolar walls or the adjacent cranial
Fig.16 Skull of Saimiri orstedii
w. (A. S. 877), showing caries on neck
of right 11 (left I2 lost and alveolus closed).
Fig. 17 Skull of Pitliecus rhesus 0 c. (P. A. L. 132), showing alveolar abscess
above P1 and caries on the neck of P 1 and P2.
ERUPTION AND DECAY OF TEETH IN PRIMATES
561
structures showed unquestionable signs of pathological destruction of the bony tissue, having originated in connection
with the dentition. It is evident, therefore, that several different conditions are here combined under the general term
Fig.18 Lower jaw of Gorilla gorilla ,j’w. (P. A. L. 13), showing extensive
abscees formation on alveolus of right C.
Fig. 19 Skull of Cebus capucinus w. (A. S. 963), showing extensive abscess
in alveolus of right C and loss of this tooth before death of animal.
‘abscess. ’ Many cases represent so-called dento-alveolar
abscesses, following frequently after the exposure of a pulp
cavity through attrition, caries (fig. 17), or fracture of a tooth.
In other, though rare, cases some mechanical force exerted
on a perfectly sound tooth may have fractured the alveolar
562
ADOLPH H. SCHULTZ
wall and thereby opened a way for suppuration of the tooth
socket. Thus, the powerful Canines of many male primates
could break the alveolar wall, before the tooth itself breaks,
in case the tooth becomes wrenched labially while employed
in fighting (figs. 18 and 19). Bone lesions on the alveolar
walls of sound teeth develop in many primates as a consequence of paradontal disease which in turn originates most
commonly from injury to the gums caused probably by food,
as has been discussed in detail by Colyer ( ’31).
Fig.20 Upper jaw of Gorilla gorilla
abscess on right M1.
d
w. (P. A. L. 13), showing alveolar
Examples of the pathological destruction of the alveolar
walls in primates, spoken of below simply as ‘abscess,’ are
shown in the figures 17 to 20. Further examples have been
published in a previous paper by the author ( ’25 ; figs. 29
and 30) and four other cases are illustrated in the book by
Coiyer ( ’31; figs. 135, 136 and 144).
After the complete loss of a tooth its alveolus becomes
gradually closed and the corresponding portion of the alveolar
process may become resorbed. The data on ‘closed alveoli’
have been collected chiefly for the purpose of demonstrating
the frequency with which monkeys and apes can outlive a t
least part of their dentition and this even in the wild state.
ERUPTION AND DECAY OF TEETH IN PRIMATES
563
The highest number of lost teeth in a single specimen was
found among higher primates in a wild adult chimpanzee with
18 of its alveoli closed and among lower primates in a wild
adult capuchin with the alveolar process for 13 of its teeth
completely resorbed. That the loss of teeth and subsequent
closure of their sockets is very rarely due to exclusively
traumatic conditions, but is most commonly caused by some
preceding disease process, appears highly probable. For
instance, among the 18 chimpanzees with the alveoli of one
or more teeth closed there exists abscess formation on other
teeth in 15 specimens and in addition caries in 7 of the latter
cases.
By far the highest numbers of abscesses for sipgle specimens are found among gorillas and chimpanzees. The record
among the latter is held by a wild, old female with abscesses
on 17 of her teeth, and among the former 18 abscesses are
present in a wild, old male (G.gorilla) and 16 abscesses in
each of two other wild males (1G . gorilla, old and 1G. beringei, adult). In all the other genera this number never exceeds
10 and in only two instances 8.
On deciduous teeth caries and abscess is found very rarely
and only in captive specimens. Thus, caries of deciduous
teeth was observed only in 3 captive macaques and abscess
formation on the alveoli of deciduous teeth only in 1 captive
capuchin, 8 captive macaques, and 4 captive chimpanzees.
These cases, appertaining to the deciduous dentition, are
omitted in tables 22 to 27 and in the discussion to follow.
Caries of permanent teeth and abscess on the alveoli are
very rarely seen in primates with incompletely erupted dentitions. I n the entire material of 982 young primates caries
was observed in only 1 wild and 4 captive specimens and
abscess in only 3 wild and 2 captive specimens. A closed
alveolus, following the loss of a tooth, was never seen among
the young primates examined. After the completion of the
eruption of all permanent teeth and with the progress in attrition caries, abscess and loss of teeth become rapidly more
frequent. This is abundantly demonstrated by tables 22 to 25
564
ADOLPH II. SCHULTZ
TABLE 22
Aye changes in the percentage frequerrcy of specimens with carious, abscessed,
and lost teeth (and average number o f teeth affected in these spechens) in
wad higher primates. I n young wild higher primates abscess is pesent only i n
one gori2Za (one tooth) and in one chimpanzee (three teeth), whereas caries and
loss of teeth are completely lacking. None o f the oaptive higher primates show
caries. abscess, and loss of teeth
WILD
HYLOBATBS
-Adult
Age
Specimens
Caries
Percentnge of specimens
Average number of teeth
Abscess
Percentage of npeeimens
Average number of teeth
Closed alveolus
Percentage of specimens
Average number of teeth
151
1.s
3.0
Adult
Old
Old
Adult
Old
Adult
Old
98.5
1.5
12.5
-- ~
-75
94 48
4.5
21
66 64
1.1
6.7 29.2
4.4
4
.
0
1
.
0
2.7
-- - 2.5
14.6
58.5
2.3
4.1
4.0
18.1
1.0
1.8
I
1.3
2.61.0
~
--
18.7
58.3
6.7
61.9
2.0
4.2
8.0
25.0
5.2
5.5
1 1
3.4
1.0
0
fO.5
0
1.s
--
4.8
3.d
9.4
3.0
1.0
3.0
TABLE as
Age changes in the percentage frequency of 8pe&ens with carious, abscessed, and
lost teeth (and average number of teeth afected in these specimens) in wild
( w . ) and captive (0.) monkeys o f the subfamily Lasiopyginae
1
QENUS
Specimens
Caries
Percentage of
specimens
Average number of teeth
Abscess
Percentage of
specimens
Average numberofteeth
W.
C.
----C.
W.
--
LASIOPYQA
--
82
233
0
1.3
0
W.
C.
PITHECUI
1.3
w.
c.
w.
c.
0
0.4
0
w.
c.
w.
0
0
0
e.
0
1.o
Adult
Old
97
31
73
26
21
34
32
4
26
6
2.1
9.7
15.7
23.1
0
0
2.5
2.7
2.0
2.3
0
2.9
0
0
5 .2
9.7
50.1
11.5
4.8
0
6.2
0
50.7
66.7
0
2.6
1.6
1.3
2.5
2.3
5.0
0
1.0
1.6
2.0
1.0
d.1
11.0
11.5
0
53.3
0
0
2.1
2.3
1.0
0
4.2
1.5
0
0
3.0
2.0
Young Adult
Adult
Old
61
39
84
18
28
4
7.7
553
1.6
0
2.4
16.7
$1.4
50.0
1.0
1.0
1.5
2.7
1.8
3.5
Old
--
--
- - - -- - __-
2.0
0 4.5
-
0
0
0
Closed
alveolus
Percentageof
specimens
Averagenumberof teeth
0
2.5
0
1
0
0
55.7
25.0
0
1.3
1.2
10.7
5.6
0
5.0
0
0
5.0
--
565
ERUPTION AND DECAY OF TEETH IN PRIMATES
TABLE 24
Age changes in the percentage frequency of specimens with Catiowr, abscessed,
and lost teeth (and average number of teeth affected in these specimens) in
wild m n k e y s of the subfamily Colobinae. I n dl seventy-nine young Colobinae
caries, abscess, and loss of teeth are completely Zucking. The seven captive
svecimens examined show no defects in their dentitions
~
COLOBUS
WILD
Age
Adult
Specimens
Caries
Percentage of specimens
Averaee number of teeth
Abscess
Percentage of specimens
Averagenumber of teeth
Closed alveolus
Percentage of specimens
Average number of teeth
51
NAEALXS
PYOAT-
Old
Adult
Old
Adult
Old
8
29
12
180
92
0
0
0
0
0
0
0.6
1.1
1.0
2.0
-~--____---
0
0
I I I i8I I
S.9
18.5
5.4
5.6
19.6
1.0
1.0
1.0
1.3
2.0
0
0
TABLE 25
Age changes in the percentage frequency of specimens with cariolls, abscessed, and
lost teeth (and average nwnber of teeth affected in these specimens) in wild
platyrrhines. None of the y m g platyrrhines have caries, abscess, and loss of
teeth. Among the captive p h t p - h i n e s wries is not observed, abscess occurs Q
8 Ateles (adult) (3 teeth), in 1 Cebw (adult) (1 tooth) and 1 Cebw ( O M )
(3 teeth) and loss of teeth in 1 Cebus (adult) ( 5 teeth)
WILD
Ape
I--
ATEUS
-I-
I
Adult
Old
Adult
--
Specimens
Caries
Percentage of
specimens
Average number of teeth
Abscess
Percentage of
specimens
Average nnmberof teeth
Closed
alveolus
Percentage of
specimens
Average nnmberof teeth
93
1
CEBUS
Old
ALOUATTA
Adult
Old
OBDIPOYIDAS
--
--
hdult
Adult
---
Old
63
70
16 132 77
39 a 28
-Z5.0
I I
0
1.S
SJ
14.5
2.3
1.7
2.0
--
SJ
38.8
1.7
2.5
1.2
2.0
1.2
2.2 ----
11.4
5.7
0
7.9
5.7
0
2.2
5.0
u.5
0
s.0
I
1.0
$8.1
I
2.6
10.8
50.0
Old
5
I___
14.3
$0.0
1.0
-
1.2
2.0
-
1.0
5.1
25.0
S.6
40.0
1.0
2.o
2.0
5.1
19.5
0
1.o
-
1.0
0
AYBBICALJ JOUBNAG 01 PEYSICAL ANTHBOPOLOQY, VOL. SIX, NO. 4
1.0
-
0
0
-
566
ADOLPH H. SCHULTZ
and, particularly, by the summarizing data in table 27. I t
is very evident that, whenever the series of specimens are
sufliciently large to give a representative picture, the percentages of specimens with the different pathological conditions
increases tremendously from young to adult and from adult
to old age.
Among the higher primates (table 22) caries is comparatively rare in gorilla, whereas surprisingly frequent in chimpanzee and orang-utan. This is in agreement with the
corresponding results of Colyer (’31,p. a),
but the percentages of specimens showing caries are very considerably higher,
according to the writer’s observations than according to the
data by Colyer. The latter discrepancy exists also in regard
to most the other primates and calls for some comment which,
however, may not offer a complete explanation for these
puzzling differences in results. To begin with, Colyer does
not subdivide his material according to age, and even slight
differences in the age distribution of the specimens examined
can change the average incidence of caries very significantly.
For instance, in the miter’s series of orang-utans the percentage of specimens with caries amounts to 0 in young animales, to 4.4 in adult ones, and to 28.5 in old ones. The
average percentage of the entire series of 95 orang-utans
happens to be 8.4,but would differ a great deal with changes
in the proportion of young or of old specimens. I n the series
of 254 orang-utans examined by Colyer without reference to
age caries occurred in 2.4 per cent of the skulls. In a series
of 194 other orang-utans, all with completely erupted dentitions, Selenka (1898) found 10 specimens (=5.2 per cent)
with caries.
There exist still other factors, besides age, which can influence the frequency with which caries is found. In the course
of his work in different museums, the writer gained the impression that particularly the older collections, made chiefly
for taxonomic purposes, contain comparatively few skulls of
really old specimens and few with extensive pathological defects in the dentitions. The suspicion appears, therefore,
ERUPTION AND DECAY OF TEETH IN PRIMATES
567
quite justifiable that some field collectors have given preference to ‘normal’ skulls with perfect dentitions and have discarded specimens with symptoms of extreme age or of evident
disease. I t must also be taken into consideration that many
field workers collect usually “one large male and one typical
female” from each locality, i.e., only two individuals out of
an entire local population. With the uneven representation
of the different ages within a group of primates (as well as
for certain other causes, as differing degrees of curiosity,
speed, aggressiveness, etc.) adult specimens are secured in
nearly all instances, whereas old ones only in exceptional
cases. These may be the reasons, why, for instance, 15 of
the 19 skulls of wild chimpanzees, showing caries, are in the
Hamann Museum of Anatomy and Comparative Anthropology, in which detailed taxonomic problems play but a
minor role, whereas only 4 chimpanzees with caries could be
found in all the other collections visited by the author. In
other words, caries among adult or old chimpanzees exists
in 20.3 per cent of the specimens in the Hamann Museum,
whereas in only 7.5 per cent of all the other adult and old
chimpanzee material examined. For probably the same reasons the taxonomic collections of the U. S. National Museum
and Biological Survey contain, e.g., among their material of
43 wild, adult and old capuchins only 2.3 per cent of specimens
with abscess formation and among 49 wild, adult and old
spider monkeys only 6.1 per cent of cases showing abscess.
In the corresponding series of the author’s collection these
percentages are much higher, namely, 11.9 for 42 capuchins
and 16.8 for 107 spider monkeys. This material had been
collected in the field by the writer, who had carefully saved
every skull, regardless of age or of any pathological conditions, endeavoring to secure really representative samples of
entire monkey populations.
Besides age and the possibility of selection of material
according to the chief aim of some collections, there exists
in all likelihood a third factor which can influence the frequency of the occurrence of caries, etc. This factor is in a
568
ADOLPH H. SCHULTZ
sense a geographical one and is best indicated by the following example: Of 11 specimens of Ateles geoffroyi from the
jungle near Talamanca, Costa Rica, 4 show caries on the
crowns of the lower M1 and M2. In this locality, therefore,
caries occurs among spider monkeys in 36.4 per cent of the
cases. Among the other 145 wild adult and old spider monkeys from different localities (but including a majority of
specimens of the same species, A. geoffroyi) caries is present
in only 5.5 per cent of the cases. This su5ices to show that
local varieties of a species may in some instances manifest
a predisposition or at least a special susceptibility for caries.
That some types of primates possess a striking resistance
to carious infections is clearly demonstrated by the data in
table 26 (compare also tables 23, 24 and 25). Caries in the
subfamily Colobinae occurs in only 0.4 per cent (only 2 langurs) of the entire material, whereas in the closely allied
subfamily Lasiopyginae this percentage amounts to 4.6.
Among platyrrhines there exists an even more marked difference in this respect, since caries is found in only 0.3 per cent
of howlers (only 1 of 282 specimens), but in 9.0 per cent of
all other New World monkeys12 examined. The general percentage frequencies of abscesses and of closed alveoli do not
differ anywhere near as much in the various groups of primates, but the data in table 26 show convincingly that abscess
and closed alveolus are in general more common in the higher
than in the lower primates.
Table 27 demonstrates the fact that captivity influences very
markedly the frequency of cariesfs in all age groups, but
changes the frequency of abscess very little1* and that of
'According to Colyer ( '31, p. 44), not only Alouatta, but also the platyrrhine
genera Aotaa, Callicebus, Cacajao and Brachyteles (not examined by the d t e r )
are free from caries in the wild and captive states.
'A much greater frequency of caries in captive than in wild monkeys baa also
been found by Turner ( '14) and by Colyer ( '31). Incidentally, the former author
states that caries is found in 5.3 per cent of the skulls of wild monkeys in the
British Museum.
%Judgingby the small series of old captive specimens, absceases are considerably
less frequent during old age in captive than in wild monkeys.
569
ERUPTION AND DECAY OF TEETH IN PBIMATES
closed alveoli not at all. The greater frequency of caries in
captive than in wild primates can probably be traced back
to inadequate diet in the state of captivity, affecting particularly animals captured young. Dietary insdciencies, however, will not explain the much more striking differences in the
TABLE 26
Percentages of specimens with caries, abscess, and closed alveolus in different
grovps of primates (all ages oombined, but considering
only d i d specirnene)
I
I
WILD PBIMATLS
or u AQLS
1
SPLCIYZNS
Large apes and gibbons
Rubfamily Lasiopyginae
Subfamily Colobinae
Platyrrhineswithout
Alouatta
Geuas Alouatta
I
PLBCLNTAO= or spmmmxsw
Cariea
I
AbLbacesa
rm
Cloned dvaolns
744
504
451
5.2
4.6
0.4
20.2
9.5
7.1
6.7
4.6
2.2
413
282
9.0
0.3
8.2
2.9
3.5
7.4
TABLE 27
Age changes in the percentages of specimens showing wries, abscess, or closed
alveolw on one or more teeth in wild and in captive primates
(all genera combined)
I
I
WILD SPLOIYLNS
C-IPLOIXENS
AQL
Total of specimens
Caries
Abscess
Closed alveolus
Young
Adult
587
1172
635
0.2
0.5
0
2.9
6.3
2.6
10.5
32.9
11.7
Old
-~
1.0
0.5
0
24.4
21.9
12.2
incidence of caries between certain groups of wild primates.
Thus, the writer has shot howlers and capuchins in the same
trees, where they had been eating the same food, as shown
by their stomach contents, yet caries is found in 25 per cent
of old capuchins, whereas in only 1.3 per cent of old howlers.
I t has been shown above that the dentitions of certain types
of primates are much more susceptible to partial destruction
by caries than are the dentitions of other types. It will now
570
ADOLPH H. SCHULTZ
be demonstrated that certain teeth are much more likely to
have carious cavities than are other teeth. This is evident,
first of all, from the following finding: Of the total of 261
teeth with caries only 115 teeth, or 44 per cent, are asymmetrical in distribution within the same dentition, whereas
56 per cent of these teeth are corresponding teeth on both
sides of the same jaw. If caries were to affect the 32 or 36
teeth of a dentition indiscriminately, one would never encounter 73 pairs of right and left teeth in this series of 122
specimens showing caries, and this on an average in only
2.1 teeth per specimen. Since in over half the cases with
caries the same tooth is affected in the right as in the left
half of the jaw, it is certain that the different types of teeth
possess widely varying degrees of constitutional resistance
to caries.I6 This conclusion is also supported by the data
presented in figure 21. According to the diagrams showing
the percentage distribution of caries among the different teeth,
the I1 and the M1 bear the relatively highest numbers of
carious cavities. I n wild catarrhines caries is found on
Incisors in 50 per cent of all affected teeth and on M1 in 16
per cent; in captive catarrhines the Incisors show caries in
only 34 per cent, but the M1 in 38 per cent of the cases. Judging by the corresponding data of Colyer (’31, p. 44), this
difference between wild and captive catarrhines is even more
pronounced in his extensive material. According to the latter
author as well as according to the writer’s results, caries
in platyrrhines exists chiefly in the Incisors and Molars,
cavities in the other teeth occurring in only 9 per cent of all
cases of caries according to Colyer and in only 25 per cent
according to the author. I n both, catarrhines and platyrrhines caries is somewhat more frequent in the upper than
in the lower jaw.
“Of the total of 770 teeth with abscesses 61 per cent are asymmetrically
distributed within single dentit.ions, and only the remaining 39 per cent show
aymmetncd disposition, affecting corresponding teeth in the right and the left
half of a jaw. It must also be considered that the average number of abscesses
per specimen with this condition amounts to 2.6, i.e., to more than the corresponding average for caries; the higher this average the greater the probability for
symmetrical distribution by chance alone.
ERUPTION AND DECAY OF TEETH I N PRIMATES
571
As shown by the lower left diagrams in figure 21, there
exists comparatively little discrimination among the different
teeth in regard to abscess, except that the Canines of platyrrhines have alveolar abscesses with astonishing frequency.
Abscesses on Canines may be connected with fighting among
males, causing fractures of their large Canines or of the
corresponding alveoli. In Alouatta, e.g., abscesses on Canines
I
I
Fig.21 Percentage frequencies with which caries, abscess, and closure of
alveolus are found in the different teeth. The distribution of the incidence of
caries among the various teeth is shown in the upper half of the picture, for
catarrhines and for platyrrhinee in the two diagrams on the left, for wild and
for captive catarrhines in the two diagrams on the right. The d i a g r a m a in the
lower half of the figure show the distribution among the various teeth of abscesses
(on the left) and of closed alveoli (on the right).
572
ADOLPH H. SCHULTZ
are recorded for 15 out of 95 adult or old males (=15.8
per cent), but for only 3 out of 115 females (= 2.6 per cent).
In some catarrhine genera abscesses on the Canines of males
are even more frequent than in the just mentioned example
of platyrrhines. Thus, in adult or old gorillas this condition
exists in only 6 out of 88 females (=6.8 per cent), but in
35 out of 157 males (= 22.3 per cent). The excessive enlargement of the Canines in males of some primates has evidently
its decided disadvantages, since it is very apt to concur sooner
or later with a developing abscess. I n Old World as well
as in New World primates abscesses, just as carious cavities,
are more frequent on the M1 than on the M2 and more frequent on the latter than on the M3. Abscess formation, just
as caries, is on an average somewhat more common in the
upper than in the lower jaw.
As shown by the diagrams in the lower right quarter of
figure 21, closed alveoli are more common for Incisors, particularly 12, than for any other teeth. In catarrhines the
premature loss of teeth becomes, in general, less and less
frequent from the Incisors to the last Molars. This does
not correspond to the relative frequency of caries and abscess
in the different teeth, nor to the progress of attrition. This
unexplained lack of correlation between the loss of teeth and
the pathological hdings on teeth is clearly shown by the
following example: In catarrhines the alveoli of the I2 are
closed in 28 per cent of all cases of closed alveoli, whereas
the alveoli of the M1 are closed in only 7 per cent of all
cases. On the other hand, caries affects the I2 in only 11
per cent of all cases of caries, whereas the M1 in 23 per cent
of the cases, and abscess is found on the I2 in 9 per cent of
all cases of abscess, but on the M1 in 20 per cent. In other
words, caries and abscess occur on the I2 less than one-half
as often as on the M1, but the 12 are lost and their alveoli
are closed four times more frequently than the M1.
It remains to compare briefly some of the data on dental
pathology in apes and monkeys with the corresponding con$tions in man, particularly the lower human races. These
ERUPTION AND DECAY OF TEETH I N PRIMATES
573
comparisons have to be restricted to a few examples, chosen
at random from the mass of available data appertaining to
the frequency and distribution of caries, etc., in man.
Pickerill ( ’23) has collected some convenient statistics
showing the incidence of carious dentitions in different racial
and other groups of man. These percentages range between
1.4 (Eskimos) and 20.8 (Negroes) among the colored races
and amount to anywhere from 86 to 99 in different groups
of modern whites. A comparison with table 26 shows clearly
that specimens with caries are more common in many groups
of monkeys and apes than in some few human races. The
percentage of carious teeth, however, is probably always
higher in modern man than in other primates. In full grown
wild gibbons and large apes there are on an average only
0.6 per cent of all teeth carious, in full grown wild lower
catarrhines this percentage amounts to only 0.2, and in full
grown wild platyrrhines to 0.3. According to Pickerill, the
percentages of carious teeth vary in ‘uncivilized races’ between 2 and 7 and in ‘highly civilized races’ between 15 and 52.
In Seminole Indians, Hamlin (’33) finds 29.7 per cent of all
teeth to be carious, whereas for Bantus, Shaw (’31) obtains
a corresponding percentage of only 1.85. Age iduences the
frequency of caries very profoundly not only in apes and
monkeys, but also in man. For instance, among boys of
Prague carious permanent teeth were found in 25 per cent
of individuals 8 years old, in 74 per cent of individuals 12
years old, and in 90 per cent of individuals 19 years old;
in relation to the total number of permanent teeth the cases
of carious teeth amount to (upper jaw) 3.5 per cent at 8 years,
7 per cent at 12 years, and 25 per cent at 19 years (Sub, ’19).
Again as in other primates, caries in man affects corresponding teeth on the right and the left side of a jaw much
more frequently than different forms of teeth in the same
dentition. Thus, Suk (’19) has reported that of 1764 carious
teethsin Prague children 546 (belonging to 152 individuals)
were asymmetrically distributed, whereas 1218 decayed teeth
(of 364 individuals) were found in couples, i.e., symmetrically
disposed on the right and left sides of a jaw.
A Y P B I C A N JOURNAL OF PHYSICAL ANTHROPOLOGY, VOL. XlS, NO.
4
574
ADOLPH H. SCHULTZ
The somewhat greater frequency of caries in the upper
than in the lower jaw of monkeys and apes is also in agreement with this relation in man, according to the majority
of observers.
It has been shown that caries in apes and monkeys affects,
in general, most frequently the M1 and the upper 11. Different human races differ apparently a good deal in regard to
this relative susceptibility to caries of various teeth. For
instance, in children of Prague and in young Zulus caries
is found on the M1 with the highest and on the M2 with the
second highest frequency, but on the I1 and I2 caries is rare
(Suk, '19). The same relation exists in adult Bantus (Shaw,
'31) and in skulls of predynastic Egyptians (Ruffer, '20).
In Seminole Indians caries affects the different teeth with
comparatively little discrimination and occurs quite frequently
on the upper Incisors (Hamlin, '33). In other Indians
HrdliEka ( ' 0 8 ) found caries most commonly on the Premolars and Molars. I n the ancient inhabitants of Guam the
M2 are carious much more frequently than any of the other
teeth (Leigh, '30).
It must sdlice here to state the general conclusion that the
frequency of the various forms of 'alveolar abscess' in, particularly old, apes is a t least as great as the general average
frequency of these conditions in modern man, though different
human races vary a great deal in this respect. That dental
abscesses, due to a variety of causes, were already very common in ancient human populations has been clearly demonstrated by many investigators, e.g., Ruffer ( '20), MacCurdy
( '23), Chappel ( '27), and Moodie ( '31).
I n regard to ante-mortem loss of teeth, there exists a very
striking difference between apes and monkeys on one side
and man on the other. In the latter the M3 are, as a rule,
lost much more frequently than any of the other teeth, as
shown, for instance, by Leigh ('30) for the ancient population of Guam and by Stewart ('31) for the pre-Columbian
Peruvians. I n sharp contrast to this, the M3 of apes and
monkeys are more rarely lost before death than the other
teeth.
ERUPTION AND DECAY OF TEETH IN PRIMATES
575
SUMMARY
This paper represents chiefly a collection of information
on some relations between age and dentition in monkeys and
apes and thus it furnishes comparative data, needed in the
interpretation of age changes in the dentition of man. The
available information is in part still very fragmentary and
as yet far from permitting many general conclusions. For
this reason only the more adequately supported results will
be listed in the following brief enumeration of findings.
The deciduous dentition erupts at earlier ages in macaques
and gibbons than in the large apes and at much earlier ages
in all apes than in man.
The tentative, average age of eruption of the permanent
dentition reaches in the macaque from the second half of the
second to (probably at most) the middle of the eighth year,
in the chimpanzee from the end of the third to the end of
the tenth year, and in man from the beginning of the seventh
to the end of the nineteenth year. In all these primates the
ages at which the various teeth appear fluctuate individually
to a very considerable extent. Not only in man, but also
in the chimpanzee and in the macaque there exists a relatively long resting period before the eruption of the last
Molars. In all primates examined, except man, the eruption
of the first Molars is followed by a comparatively long intermission before further teeth are being added to the permanent
dentition.
The detailed survey of the sequence of eruption of the permanent teeth in monkeys and apes is based chiefly upon
observations on large series of skulls of which a total of 2908
specimens has been examined. The permanent dentition
starts in all p r i w t e s with the eruption of the lower M1,
followed by that of the upper M1, except in man in whom
the lower I1 can frequently be the second permanent teeth.
In squirrel monkeys and langurs the M2 appear after all the
M1, whereas in the other primates examined the I1 erupt
as the second form of permanent teeth. In gnerezas the M2
appear, as a rule, before the 12, but in the great majority
576
ADOLPH
E. SCHTJLTZ
of monkeys and apes this relation is reversed, the I 2 following immediately after the I1 and the lower I2 preceding the
upper 12. In all primates, except man, the Premolars erupt
in rapid and varying succession after the M2 have been added
to the dentition, but before the Canines make their appearance. The lower M3 and subsequently the upper M3 are thc
last teeth to erupt in all primates, with the exception of langurs (and lower jaw of squirrel monkeys) in which the M3
appear before the Premolars and Canines. This early addition of the last Molars is probably to be regarded as a primitive condition and occurs in the same monkeys which are
distinguished by an exceptionally early eruption of the M2.
The sequence of eruption of the permanent dentition of
modern man has become much more specialized than that
of any other primate. These extreme changes consist in the
eruption of the Incisors following generally without any resting period that of the M1, in the eruption of the Premolars
and Canines before that of the M2, and in the frequent appearance of the lower C before the eruption of the P2. Two
specimens of Neanderthal man of suitable dental development
still show the less specialized, simian condition of the eruption
of M2 before the appearance of all Premolars.
I n many primates, including man, the Canines of males
erupt slightly later and often more slowly than those of
females.
With comparatively few exceptions, the teeth of the lower
jaw erupt before the corresponding teeth of the upper jaw,
this difference being most regular and pronounced in regard
to the Molars.
The review of the scattered and frequently conflicting statements by other authors regarding the sequence of eruption
of the teeth in.primates reveals the fact that the many erroneous conclusions in the literature are mostly based upon entirely inadequate series of observations.
Noteworthy attrition of the permanent .teeth is very rare
before the completion of the dentition. Marked attrition
appears first on the M1, the Inoisors and, less regularly, on
ERUPTION AND DECAY OF TEETH I N PRIMATES
577
the Canines. The M2 become worn after the just mentioned
teeth, but usually before the Premolars. The M3 are generally the last teeth to become affected by advanced attrition.
Among old specimens the Incisors and Canines are more frequently worn to the gums than any other teeth. Extreme
attrition is most common among the higher primates and
least frequent among the platyrrhines (except Ateles).
The base suture and the sagittal suture are with very few
individual exceptions open during the entire period of dental
eruption. After the closure of both these sutures marked
attrition of the teeth becomes, in general, much more common
than among skulls with one or both sutures still open. The
numerous correlations between suture closure and dental
attrition in the different primate genera are shown more
clearly and briefly in table 20 than they could be summarized
here.
Deviations from the normal conditions of the permanent
dentition are found with varying and at times surprisingly
high frequencies in all the major groups of primates examined. Striking reductions in the size of teeth occur chiefly
in the M3. Such vestigial M3 are particularly frequent in
gibbons and among the platyrrhine spider monkeys, capuchins,
and squirrel monkeys. Among the same primates, except the
last named group, the .complete elimination of M3 is also
much more common than in the other genera. Fourth Molars
are found chiefly among the large apes. The congenital lack
of Incisors and of Premolars occurs in rare instances among
a wide variety of monkeys and apes. Marked crowding of
teeth is much more common in the case of Incisors and Premolars than in the case of other teeth and is more frequent
in the upper than in the lower jaw. Crowding of Incisors
is most commonly met with in langurs, whereas displacement
of Premolars is most frequent in chimpanzees and in howlers.
Impacted teeth have been observed in 24 specimens of which
12 are anthropoids. Abnormally long retained deciduous
teeth are present in 1& fully adult primates, belonging to
seven different genera.
578
ADOLPH 11. SCHULTZ
Caries and alveolar abscesses are extremely rare on the
deciduous teeth of monkeys and apes. On the permanent
dentition these pathological conditions become very much
more frequent in adult than in young and in old than in adult
specimens.
Carious teeth are rare in gorillas, but comparatively frequent in chimpanzees and orang-utans. Similar, wide differences in regard to the frequency of caries exist in other groups
of primates. Thus, caries is very rare in Colobinae, whereas
quite common in Lasiopyginae, and it is extremely rare in
howlers, but comparatively frequent in other platyrrhines.
The frequencies of abscess and of loss of teeth do not M e r
nearly as much in different types of primates as does the
incidence of caries. In over half the dentitions with caries
the cavities occur in the same teeth on the right and the left
side of a: jaw. Caries affects the I1 and the M1 much more
frequently than any of the other teeth and it is found somewhat more commonly in the upper than in the lower jaw.
Abscesses are much less unevenly distributed among the different teeth, except that they are found in an exceptionally
high percentage of cases on the Canines of (male) platyrrhines.
The I 2 of monkeys and apes become prematurely lost in
a higher proportion of cases than any of the other teeth; the
I1 stand second in this respect and the M3 last.
By means of preliminary comparisons, it is shown that the
pathological conditions of the dentition of man are in many
respects very similar to, in other respects quite different from,
the corresponding conditions in apes and monkeys.
The combined data on advanced attrition of teeth and on
the gradual pathological destruction and loss of teeth and of
alveolar walls reveal a surprising prevalence of these conditions in simian primates of old age. The dentition begins
to break down before the termination of the normal life span
not only in man, but in apes and monkeys as well. A decrease
in the normal usefulness of the dental apparatus, brought
about by extreme attrition, various dental disease processes,
and premature loss of teeth, is, in general, more common in
ERUPTION AND DECAY OF TEETH I N PRIMATES
579
the higher than in the lower primates. This suggests the
tentative conclusion that the probably general, evolutionary
prolongation of the life span of anthropoid apes and man is
not accompanied by a corresponding improvement in the
durability of the misnamed ‘permanent’ dentition.
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