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Endocranial capacity of Western Australian Aboriginal crania Comparisons and association with stature and latitude.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 84:399405 (1991)
Endocranial Capacity of Western Australian Aboriginal Crania:
Comparisons and Association With Stature and Latitude
L. FREEDMAN, W.F.C. BLUMER, AND M. LOFGREN
Centre for Human Biology and Department of Anatomy and Human
Biology, University of Western Australia, Nedlands W A 6009 (L.F.,
W.F.C.B.) and Department of Anthropology, Western Australian Museum,
Perth W A 6000 (M.L.), Australia
KEY WORDS
Australian Aborigines, Allometry, Climate
ABSTRACT
The endocranial capacities (ECCs) of 73 Western Australian
Aboriginal crania were estimated. Using water-standardked mustard seed,
ECCs were (in cm3) males-X 1,239, S.D. 92.3; females-X 1,118, S.D. 77.5.
The male and female mean values were smaller than those previously published for Australia as a whole; sexual dimorphism (9.7%)was also slightly
lower. Comparison of the Western Australian Aboriginal sample with a large
Danish sample (Pakkenberg and Voigt, 1964; Holloway, 1980) permitted
analysis of factors underlying sex and population differences in ECC. In both
samples about 40% of the mean sex differences in ECC could be related to
stature differences; for each sex almost 213 of the differences between the
Western Australian and Danish means appear to be associated with differences in stature and latitude. Allometric adjustments are also involved.
Most of the studies of the endocranial capacity (ECC) of the Australian Aborigines
are based on small samples and the techniques used are often not outlined (e.g., Morant, 1927). In the present study, using a
water-standardised, mustard seed technique to measure ECC, we report on a substantial sample of crania from Western Australia and compare our results with those of
two earlier studies of Australian Aborigines
(Morant, 1927; Wagner, 1937) and also with
a large, well-anal sed Danish sample of
brain weights (Pak enber and Voigt, 1964;
Holloway, 1980). We use t e latter comparison to investigate the basis of sexual and
population variations in ECC.
Most of the specimens had been sexed for
three previous studies (Mar etts and Freedman, 1977; Freedman anc f Lofgren 1981;
Milne et al., 1983) but all were re-assessed
(independently by L.F. and M.L.) for the
present investigation, using the seven best
morphological cranial sexing features described by Larnach and Freedman (1964)
and, when present, post-cranial bones (especially the pelvis-Davivongs, 1963). In the
original description of the LarnachFreedman techni ue, using a coastal New
South Wales samp e sexed by pelvic bones, it
was concluded that 90-95% were correctly
assessed. On a Murray Valley sam le, sexed
by pelvic bones, Brown (1981)foun 92.5%of
the female crania and 91.5% of the male
MATERIALS AND METHODS
crania could be correctly assessed by the
The s ecimens measured for this study Larnach-Freedman technique.
consiste of 73 Western Australian crania
Methods
(51male and 22 female) from the collection of
It is extraordinaril difficult to get repeatthe De artment of Anthropology, Western
Austra ian Museum, Perth. Almost all are able estimates of E C as the irregularity,
the result of chance findings of burials and porosity, fissures, and foramina of crania
none are believed to be of great antiquity. present difficult challenges (Todd, 1923;
For 60 of the specimens specific localities Keen, 1951). The mustard seed, water-stanwere available (Fig. 1). For a few crania,
some minor plasticine reconstruction was
ReceivedMay 11,1989; accepted September 21,1990.
necessary.
I R
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0 1991 WILEY-LISS, INC
7
8
8
400
L. F R E E D M ET AL.
WESTERN AUSTRALIA
SCALE
I00 290
STATUTE MlLES
o Male
/?
Female
- - - _ ~
~
material listed above (Fig. 1). Descriptive
ECC statistics were calculated, by sex, for
each region and for the sample as a whole
(Table 1, 2b). The regional samples by sex,
and also the total male and female samples,
were compared by “t” tests. Sexual dimorphism was also examined by the formula of
Tobias (1975): (male mean - female mead
male mean) x 100, and also by a histogram
(Fig. 2).
RESULTS
Table 1 lists the basic statistics for the
water-standardised
mustard seed ECCs of
E
the 73 Western Australian crania. The numbers in the regional samples are small, especially in the case of the females. No significant differences at the 5% level were found
by “t”tests in either the maIe or the female
regional sample comparisons, nor were there
any clear trends in the data. Therefore, the
samples were pooled for further analysis
(Table 2b).
34
Sexual dimorphism was investigated for
1
-..
- -_
the total sample and, using the formula of
114
122
130
Tobias (19751, was 9.7%. Examined by a “t”
Fig. 1. Distribution in north (N), central (C) and test, the male-female difference was highly
south (S) coastal, and east (E) inland areas of Western significant (“t”= 5.60 with 71 d.f., P < .001).
Australia of the male and female crania examined.
The male range, 417 cm3, was greater than
that of the females, 306 cm3 (Table 2b).
Figure 2 is a histogram showing the degree of
dardised rocedure which we devised is out- overlap between the samples; 18% of the
lined in t e Appendix and gives repeatable females and 45% of the males are in nonresults. In this procedure, the volume deter- overlap regions.
mined by mustard seed is reduced by 20 cm3
COMPARISONS AND ANALYSIS
in order to make it comparable to waterIt is against a background of two widely
estimation techniques.
For many of the studies reported in the recognised findings that human ECCs must
literature (e.g., Morant, 1927), there is un- be viewed:
certainty as to whether water-standardisa1. Measurements of the endocranial cation was performed. Unless the estimation
methods are fully described and standard- pacities of a wide variety of populations of
ised, comparisons must be treated with cau- Homo sapiens supiens average about 1,420
tion. For example mustard seed estimations cm3 for males and 1,270 cm3 for females
of the ECCs of 9 Western Australian crania, (Tobias, 1981). However, there is very conreported by Woodward (1901), were mea- siderable inter- and intra-population variasured in the present study and were found to tion. Using a very large sample, including
average 61.2 cm3 larger than by our water- many different populations, Tobias (1971)
gives a range for males of 900-2,000 cm3.
standardised procedure.
Individuals appear to be able to exhibit all of
INITIAL DATA ANALYSIS
the complex behavioural patterns considProcedures
ered characteristic of anatomically modern
Because Western Australia covers over 2.5 humans within these very wide limits.
2. It is widely acce ted that endocranial
million km’, the material was initially subdivided into four samples: north, central shape, foramina and Essures make estimacoastal, south coastal, and east inland, as tions of ECC difficult and that different techwas done in the three previous studies of this niques may give values which are not compa-
v
f:
401
AUSTRALIAN ABORIGINAL ENDOCRANIAL CAPACITIES
TABLE 1. Endocranial capacities (cm3)of regional samples of Western Australian male and female crania’
Statistic
Male
N
X
SD
Female
N
X
SD
North
Central
South
East
?
9
1,251.3
88.9
16
1,261.1
93.5
10
1,210.0
87.8
6
1,238.3
80.5
10
1,222.4
110.2
4
1,098.0
91.5
5
1,100.0
114.2
9
1,132.3
71.6
1
1,097
3
1,141.7
18.5
-
‘Data on ECCs, cranial lengths, breadths, and heights on individual crania are available from the Department of Anthropology, Western
Australian Museum, Perth.
TABLE 2. Australian Aboriginal male and female endocranial cauacities lcm”i
(a) Major previous studies
Morant (1927)
Male
State
N
Northern Australia/
Territory
Queensland
New South Wales
Victoria
South Australia
Western Australia
Tasmania
Unknown
Total
18
-
X
N
1,224.2
19
38
18
39
20
33
30
215
Wagner (1937)
Female
1,287.7
1,287.7
1,311.3
1.319.6
1,255.5
1,264.3
1,310.9
1.286.8
1
1
Male
-
Female
-
X
X
N
10
1,142.5
10
1,261
27
1,141.4
19
12
39
1.149.9
15
22
7
1,277
1,320
1,388
1.278
1,231
25
9
110
1,153.8
1,149.4
1.148.0
98
1.294
N
\j
--
X
11
1.103
11
1.103
(b) Present study
State
N
x
Western Australia
51
1.239.1
Male
SD
92.3
rable (Todd, 1923; Keen, 1951). The repeat
measurements, a t different times and with
different observers using our standard procedure, lead us to believe that our method is
acceptably reproducible (Appendix A). As
noted, our water-standardised technique includes a subtraction of 20 cm3from the mustard seed estimate.
Comparisons with data in the literature are,
however, hazardous due to varying techniques of estimation. Having become fully
cognizant with the difficulties involved, we
agree with Wagner (1937)that differences of
less than 50 em3between population figures
from authors using different or less well
standardised methods, cannot be considered
significant.
Australian comparisons
There are scattered records of Australian
Aboriginal ECCs which have been estimated
~
Range
N
X
1.467-1.050
22
1.118.5
Female
SD
77.5
Range
1.248-942
by a variety of techniques for more than 100
years. In 1927 Morant collected together the
early published data. The 18 studies he summarised were made between 1865 and 1918
and included the capacities of 215 males and
110 females (Table %a). He noted that:
“. . . all capacities were accepted, although
the different methods used to determine
them might well have led to substantially
different results . . .” (p. 421).
The next, and apparently only other, large
study was by Wagner (1937). He assessed 98
male and 11 female ECCs from mainland
Australia and quotes Morant’s data for the
Tasmanians (Table 2a). The mainland sample he measured included previously undescribed material but apparently also some
crania included by Morant (1927).
Com arisons between the regional samples o Morant (1927) and Wagner (1937)
show mean differences as great as 76.7 cm3
and the difference for their Western Austra-
P
402
L. FREEDMAN ET AL
14
12
4
8
Fig. 2. Histogram of male and female Western Australian Aboriginal endocranial capacities (cm3).
lian male samples is 24.5 cm3(Table 2a). The because the extra volume of the menin es,
male mean values for the present study of about 50 cm3,is balanced by the amount t at
the Western Australian males (Table 2b) is a skull shrinks, 50-60 cm3, when it is dried
similar to that of Wagner but 16.4 cm3 less (Todd, 1923).
than that of Morant. Compared with the
On mean values, the Danish male and
Australia-wide totals, the present Western female sample ECCs (above)are each considAustralian male value is about 50 cm3 less
eater than those for Western Australia ( able 2bbmales 167.5 cm3, females
than those of both Wagner and Morant. The erably
female Western Australian mean ECC is 153.6 cm3.
The degree of sexual dimorphism is simi29.5 cm3 less than that of Morant’s Australia-widefigure and sexual dimorphism in the lar in the Western Australian and Danish
present sample (9.7%)is also lower than that samples, 9.7% and 9.6%, respectively. In a
ofMorant’s sample (10.8%).
major study of brain evolution, Tobias (1975)
has found the mean ECC sexual dimorphism
of 67 worldwide populations to be 10.57%,
Sex and population variation in ECC
with a range from 5.2% for Chinese to 18.4%
In order to investigate sexual dimorphism for Singhalese. So sexual dimorphism in
and population differences in ECC, the both the Australian and Danish Sam les is
Western Australian data were compared just slightly lower than the mean va ue for
with those of the large Danish Sam le of 502 Tobias’world range.
Brain size and stature: Pakkenberg and
males and 165 females (Pakken erg and
, 1964), recently fully re-analysed by Voigt (19641, in a linear regression analysis
vOi?
Holoway (1980). This was the only large of Danish brain weight, body weight, and
sample we could locate with which compari- stature, showed that “. . . brain weight desons could be made. As these data_were for pends significantly on height. . .” (p. 303).
brain weight in grams (males-X 1,457.2, Re-analysing the Danish data, Holloway
S.D. 119.8; females-X 1,317.9, S.D. 109.81, (1980) using partial correlation statistics,
to make the data comparable, the weights reported a significant (P < .001) zero-order
were converted to volumes using the average correlation (0.35) for males between brain
specific gravity of brain tissue, 1.036 (Vo- weight and stature but the female value
neida, 1966). Thus the Danish male brain (0.07) was not significant ( P = 0.19); the
volume (cm3)is estimated as X 1,406.6, S.D. combined male-female correlation (0.47)was
115.6 and that of the females as X 1,272.1, si ificant (P < .001).
%en examining the relationships beS.D. 106.0.These brainvolumes may be used
directly for comparison with ECCs of the tween stature and ECC, the question of aldried Western Australian crania. This is lometry needs to be considered. In order to
7-l
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AUSTRALIAN ABORIGINAL ENDOCRANIAL CAPACITIES
maintain a balance between biomechanical
and hysiological requirements with body
size c an es, “. . . a different growth rate in
different irections for different structures”
(Gans, 1974,p. 144)is usually required. If all
linear dimensions of a population increased
by a similar percentage, a 5% increase in
stature and in cranial length, breadth, and
height would result in an ECC increase of
15.8%.
Using Abbie’s(1976)Australia-wide mean
stature data (males 168.4 cm, females 157.2
cm), the male excess of stature over that of
the females is 7.1%.If each of the Western
Australian cranial dimensions (length,
breadth, and height) were greater by a similar percentage (7.1%),the male ECC would
be greater by28.2%.The differences in ECCs
actually found was 10.6%.
When the three basic cranial measurements of the Western Australian Aborigines
(Margetts and Freedman, 1977) are examined, it is found that, on mean values, the
male excesses over those of the female are
length 5.8%(male 186.5 cm, female 176.3
cm), breadth 2.5% (male 131.4 cm, female
128.2 cm), and hei ht 5.3%(male 132.5 cm,
female 125.8 cm). hus all three ercentage
differences are less than those or stature
(7.1%)and the cranial breadth excess is only
about one-third. However, in considering
these figures in relation to ECC, bone thickness and cranial contours need to be considered, and it becomes clear that breadth, with
only relativelythin bone on each side, is most
closely related to ECC. The marked development of the Australian Aboriginal browridges, especiallyin the male, greatly adds to
the external length measurement. As the
height dimension is made from basion, because of the contour shape of the cranial
base, the cranial height component of internal volume is exaggerated.
Calculations show that a 3.4%increase in
each of the three linear cranial measurements would be enough to produce the 10.6%
difference in ECC which was found. The
allometricreduction in the percentage difference in each of these three dimensions has
resulted in a 40 cm3smaller ECC than would
have been expected if each dimension was
greater by the same ercentage. It would
seem that there has een an appropriate
adaptive, evolutiona adjustment for the
new balance required etween ECC and the
greater body size in males.
In a comparison of the Western Australian
% %
8
g
t
73
Aboriginal data with Holloway’s (1980) data
on Danes, in each case the difference between males and females in mean ECC is
about 125 cm3 (Western Australians 120.6
cm3, Danes 134.5 an3)and, in stature (using
Abbie’s 1964 data for the former), it is about
10 cm (11.2 cm and 10.0 cm, respectively).
Pakkenberg and Voigt (1964) roduced a
common (for Danish males and emales) regression slope of 4.56 of brain weight on
stature. If, as an ap roximation, this regression, which takes a lometry into account, is
applied to those two PO ulations, the 10 cm
stature difference coul account for almost
50 cm3(40%)of the ECC difference between
the Western Australian and Danish samples.
Further, for each sex, the mean ECCs of
the Danes were found to be about 160 cm3
lar er than those ofthe Western Australians
(Ta le 2b) but, ain using the AustraliaY Iie, on average, Danish
wide data of Ab
males and females are each also about 5 cm.
taller than the Australian Aborigines (Australian Aboriginal males 168.4 cm, females
157.2 cm; Danish males 173.2 cm, females
163.0 cm). If the Pakkenberg-Voigt common
regression slope (4.56) is applied to these
data, the Western Australian 5 cm lower
mean height in both males and females could
account for 23 cm3of the difference in ECC.
Bruin size and latitude: In addition, latitude has been shown by Beals et al. (19841,to
have a significant correlation with ECC; for
example, larger ECCs are more often found
in very cold regions of the world. Their broad
assessment for 82 ethnic groups is that ECC
increases by 2.5 cm3 per degree of latitude
away from the e uator. The mean latitude
for the Western ustralian sample can be
taken as 25”s (15”535”S),while for Denmark it is about 56“N. This 31° latitude
se aration would lead to an expected 77 cm3
E&C! difference, which is about half of that
observed between the male and between the
female Western Australian and Danish samples. To ether with the ECC differences ascribed a ove to stature, two-thirds of the
mean ECC differences between each sex of
the two population samples could be accounted for.
The influence of latitude may be due to
climate, i.e., to its thermodynamic effects. In
the past, for mammals including the Primates, the allometric exponent for bod
wei ht-brain weight was generally consii
ere to be about two-thirds (e.g., Gould,
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%
1
%
f
B
404
L. FREEDMAN ET AL
1975) and a possible relationship with surface area was proposed. More recently, the
exponent has been revised, using a larger
number of mammalian species, t o threequarters and an association with basal metabolic rate suggested (Harvey and Bennett,
1983).Thus the Western Australian Aboriginal-Danish comparison, although being
based on stature, would seem to suggest that
stature and climate could well be associated
with ECC through factors such as surface
area and metabolic rate.
SUMMARY
In this paper we report on the endocranial
capacities (ECCs) of a series of male and
female Western Australian Aboriginal crania. Sexual dimorphism is about 9.7%. We
found no significant differences between local samples, and the mean male and female
values for the whole sample appear to be
slightly lower than those for the rest of Australia.
A large, well-analysed sample of Danish
brains (Pakkenberg and Voigt, 1964; Holloway, 1980)was used in combination with the
Western Australian Aboriginal data to analyse sex and population differences in ECC.
Differences in mean stature and in latitude
(the latter reflecting the thermodynamic effects of climate), plus allometric adjustments, appear to account for 40% of the sex
differences and two-thirds of the population
differences.
ACKNOWLEDGMENTS
We thank Dr. Matt Cartmill and three
anonymous readers for some most useful
comments on a previous version of this paper. Ms. Rita Bonjour patiently typed a number of drafts of this paper and Mr. Martin
Thompson drew the diagrams.
LITERATURE CITED
Abbie AA (1976) Studies in Physical Anthropology, Vol.
11. Canberra: Australian Institute of Aboriginal Studies, p. 77.
Beals KL, Smith CL, and Dodd SM (1984) Brain size,
cranial morphology, climate and time machines. Curr.
Anthropol. 25:301-330.
Brown P (1981) Sex determination of Aboriginal crania
from the Murray River Valley: A re-assessment of the
Larnach and Freedman technique. Archaeol. Oceania
16:53-63.
Davivongs V (1963) The pelvic girdle of the Australian
Aborigine. Sex differences and sex determination. Am.
J. Phys. Anthropol. 21:443-455.
Freedman L, and Lofgren M (1981) Odontometrics of
Western Australian Aborigines. Archaeol. Oceania
16:87-93.
Gans C (1974)Biomechanics. An Approach to Vertebrate
Biology. Ann Arbor: University of Michigan Press, p.
144.
Gould SJ (1975) Allometry in Primates, with emphasis
on scaling and the evolution of the brain. In F Szalay
(ed.): Approaches to Primate Biology. Contributions to
Primatology Basel: Karger, Vol. 5, pp. 244-292.
Harvey PH, and Bennett PM (1983) Brain size, energetics, ecology and life history patterns. Nature 306:314,
315.
Holloway RL (1980) Within-species brain-body weight
variability: A reexamination of the Danish data and
other primate species. Am. J. Phys. Anthropol. 53:
109-121.
Keen JA (1951) Standardization of the technique of
cranial capacity determination. S. Afr. J. Clin. Sci.
2:170-182.
Larnach S, and Freedman L (1964) Sex determination of
Aboriginal crania from coastal New South Wales, Australia. Records Aust. Mus. 26:295-310.
Margetts BM, Freedman L (1977) Morphometrics of
Western Australian Aboriginal Skulls. Records West.
MUS.6.63-105.
Milne N. Schmitt LH. and Freedman L (1983) Discrete
trait variation in ' Western Australian Aboriginal
Skulls. J. Hum. Evol. 12:157-168.
Morant GM (1927)A studv of the Australian and Tasmanian skulls based on "previously studied measurements. Biometrika 19:417-440.
Pakkenberg H, and Voigt J (1964) Brain weight of the
Danes. Acta Anat. (Basel) 5:297-307.
Tobias PV (1971) The distribution of cranial ca acity
values among living hominoids. Proc. 3rd int. 8ongr.
Primat., Zurich 1970, vol. 1, pp. 18-35.
Tobias PV (1975) Brain evolution in the Hominoidea. In
RH Tuttle (ed.): Primate Functional Morphology and
Evolution. The Hague: Mouton Publishers, pp. 353392.
Tobias PV (1981) Evolution of the Human Brain, Intellect and Spirit. South Australia: University of Adelaide, p. 19.
Todd TW (1923) Cranial capacity and linear dimensions
in White andNegro. Am. J. Phys. Anthropol. 6:97-194.
Voneida TJ (1966) Central nervous system. In JAAnson
(ed.): Morris' Human Anatomy, 12th Ed. New York:
McGraw Hill Book Company, p. 928.
Wagner K (1937) The Craniology of the Oceanic Races.
Norske Videnskaps-akademi i Oslo. I Mat.-Naturv.
Klasse No. 2.
Woodward BH (1901) Catalogue of skulls of Natives of
Western Australia in the Museum. Perth, W.A.: Western Australian Museum.
APPENDIX A
In the present study we used mustard
seeds to assess ECC. The crania were preared by blocking all of the externally visible
oramina and fissures through which seeds
might be lost when in the inverted position.
The seeds were kept under stable conditions
for the duration of the study.
In filling the endocranium, the inverted
cranium with its anterior end tilted slightly
upward was placed on a stand. Five hundred
cubic centimeters of mustard seed were
poured into a plastic funnel held with a
P
405
AUSTRALIAN ABORIGINAL ENDOCRANIAL CAPACITIES
finger blocking its outlet. The spout of the
funnel was placed just inside the foramen
magnum, and the seeds allowed to drop into
the cranium under their own weight. The
cranium and its stand were then sharp1
jerked left, right, forward, and backward:
each movement being done twice. The funnel
was refilled with seed and the procedure was
repeated. Using a beaker, the cranial cavity
was then filled to the internal lip of the
foramen magnum, and the jerking was repeated, this time more gently. Any space
that appeared after this procedure was refilled. Because of the contour of the bone just
inside the foramen magnum, a heap of seeds
commonly accumulated below the foramen
and prevented flow sideways. This heap was
eased out with a finger just before a final
filling all the way up to the external lip of the
foramen magnum.
For volume assessment, the mustard
seeds were poured from the cranium through
the same funnel into a 2 litre measuring
cylinder. They were gently agitated and
tamped to a level meniscus before reading.
Reliability of the technique was tested by
inter- and intra-observer error experiments.
A typical result of an intra-observer error
test for 10 successjve estimations (cm3) of
one cranium was X 1,320, S.D. 7.82, range
1,310-1,330. For the study, all assessments
were made by the same observer (W.F.C.B.)
and each cranium was measured three
times. If a range greater than 15 cm3 was
found, testing was continued until that degree of consistency was obtained for three
successive tests.
The technique was standardised using water on a specially prepared cranium of which
the calotte was initially removable. All relevant foramina, fissures, and sutures were
internally and externally sealed with plasticine. The whole internal surface was then
coated with rubber latex (to ensure waterproofing), followed by a coat of pol urethane
(to prevent the mustard see s adhering). The calotte was then re-attached using
“Bedacryl”.ECC was estimated using mustard seed and then water, five times each. A
typical result ofsne such test was (in cm2
mustard seed -X 1,304, S.D. 9.6; water-X
1,284, S.D. 2.2.
This, and subsequent tests, showed that
our mustard seed technique, compared to
water, overestimated ECC by about 20 cm3.
Variations in seed compacting in either the
cranium, or in the measuring cylinder, can
significantly vary the volume. Hence all our
data are given as water-standardised values.
B
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