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Asymmetric vault modification in Hopi crania.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 98:173-195 (1995)
Asymmetric Vault Modification in Hopi Crania
LUCI ANN P. KOHN, STEVEN R. LEIGH, AND JAMES M. CHEVERUD
Program in Occupational Therapy, Washington University School of
Medicine, St. Louis, Missouri 63108 IL.A.I?K.); Department of Anatomy
and Neurobiology, Washington University School of Medicine, St. Louis,
Missouri 63110 (J.M.C.); Department ofAnthropology, University of
Illinois, Urbano, Illinois 61801 (S.R.L.)
KEY WORDS
Cradleboard
Cranial growth, Finite element scaling, Hopi,
ABSTRACT
Cradleboarding was practiced by numerous prehistoric and
historic populations, including the Hopi. In this group, one result of cradleboarding was bilateral or asymmetric flattening of the posterior occipital.
We test whether cradleboarding had significant effects on the morphology of
the cranial vault, cranial base, and face. Additionally, we examine associations
between direction of flattening and asymmetric craniofacial growth.
A skeletal sample of Hopi from the Old Walpi site includes both nonmodified
(N = 43) and modified individuals (N = 39). Three-dimensional coordinates
of 53 landmarks were obtained using a diagraph. Thirty-six landmarks were
used to define nine finite elements in the cranial vault, cranial base, and face.
Finite element scaling was used to compare average nonmodified individuals,
with averages of bilaterally, right, and left modified individuals. The significance of variation among “treatment”groups was evaluated using a bootstrap
test. Pearson product-moment correlations test the association of asymmetry
with direction of modification.
Hopi cradleboarding has a significant effect on growth of the cranial vault,
but does not affect morphology of the cranial base or face. Bilateral flattening
of the cranial vault leads to decreased length and increased width of the
cranial vault. Flattening of the right or left cranial vault results in ipsilaterally
decreased length and width coupled with a corresponding increased length
and width on the contralateral side of the cranial vault. There is a significant
correlation of size asymmetry with direction of modification in the cranial
vault, but not with size or shape change in the cranial base or face.
0 1995 Wiley-Liss, Inc.
Numerous prehistoric and historic populations in North America (Hrdlicka, 1935;
Dennis, 1940; Dennis and Dennis, 1940;
Neumann, 1942; Bennett, 1973, 1975;
Droessler, 1981; Heathcote, 1986; Holliday,
1993) and the Middle-East (Ewing, 1950)
practiced cradleboarding. One result of this
practice was the flattening of the occipital
or lambdoid region (Hrdlicka, 1935; Stewart,
1937; Dennis, 1940) with either bilateral or
unilateral (flattening on either the right or
left sides) effects (Hrdlicka, 1935).An analy0 1995 WILEY-LISS, INC
sis of crania which were modified during development provides a n opportunity to examine the growth relationships of the cranial
vault, cranial base, and face. Results of previous studies have suggested that there may
be a n interrelationship of growth of these
Received Apnl 20, 1993; accepted March 17, 1995.
Address reprint requests to Luci Ann P. Kohn, Program in
Occupational Therapy, Box 8505, 4444 Forest Park Ave., Washington University School of Medicine, St. Louis, MO 63108.
174
L.A.P. KOHN ET AL.
cranial regions (Young, 1959; Pucciarelli,
1978; Babler and Persing, 1982; Babler et
al., 1987; Babler, 1988, 1989; Cheverud et
al., 1992; Kohn et al., 1993). In this paper
we evaluate whether localized modification
of the cranial vault by cradleboarding during
infancy has a significant effect on the morphology of the adult cranial base and face.
Intentional artificial cranial vault modification has been shown to have significant
effects on the growth and morphology of the
cranial base and face (Cocilovo, 1975,1978).
Two types of modification are generally recognized based on cranial vault morphology:
antero-posterior and annular modification
(Dingwall, 1931; Neumann, 1942). Anteroposterior modification was practiced by the
prehistoric people from Ancon, Peru, prehistoric individuals from Makapuan, Hawaii,
and the Songish from the Pacific Northwest
coast. This type of modification resulted
from the application of a cradleboard or
headdress to the frontal and occipital regions
of the cranial vault (Boas, 1921; Dingwall,
1931; Cybulski, 1975; Schendel et al., 1980;
Allison et al., 1981). Anterior-posterior
growth of the cranial vault is restricted, resulting in crania which appear to be short
in the anterior-posterior dimension and wide
in the medial-lateral dimension (Boas, 1921;
Oetteking, 1930; Dingwall, 1931; Anton,
1989; Mizoguchi, 1991; Cheverud and Midkiff, 1992; Cheverud e t al., 1992). In contrast, annual modification, as practiced by
the Kwakiutl and Nootka (Pacific Northwest
coast), some prehistoric individuals from
Peru (reported in Anton, 1989), and the Arawe (Blackwood and Danby, 1935) is produced by circumferentially wrapping the
cranial vault (Dingwall, 1931). Medial-latera1 growth of the cranial vault is restricted,
resulting in crania which appear to be long
in the anterior-posterior dimension and narrow in the medial-lateral dimension (Oetteking, 1930; Dingwall, 1931; Cybulski, 1975;
Anton, 1989; Mizoguchi, 1991; Kohn et al.,
1993).Antero-posterior and annular modification produce increases in the angle between the anterior and posterior cranial
base (Oetteking, 1924; McNeill and Newton,
1965; Anton, 1989). Comparable results
have been produced in experimental growth
studies of animals (Young, 1959; Pucciarelli,
1978) or crania in which the sutures were
surgically closed prematurely (Babler and
Persing, 1982; Babler et al., 1987; Babler,
1988, 1989).
Antero-posterior and annular modification of the cranial vault are produced by the
multi-directional application of pressure to
the cranial vault. Cradleboarding produces
localized, unidirectional pressure on the posterior cranial vault. As a result of differences
in pressure exerted on the cranium, cradleboarding may be expected to have a different degree of effect on the morphology of
the cranial base and face than has been observed in antero-posterior or annular modification.
Few studies have systematically studied
the effects of cradleboarding on the cranial
base and face. Heathcote (1986) examined
nonmodified and modified crania within
populations on Kodiak and Kagamil Islands
and found no evidence for a n effect of cradleboarding on dimensions outside the area
of flattening within either group. Moss
(1958)compared infants with “postural flattening” to nonmodified white adults in order
to assess the effect of localized occipital modification on growth of the cranial base. After
the statistical adjustment of infant orbital
angle to that of the nonmodified adult, Moss
found no difference in cranial base angle between the modified infants and the nonmodified adults. Bjork and Bjork (1964) assessed
Peruvian crania for a n association of asymmetry and artificial modification. Specifically, they report a significant correlation between side of the cranial vault which was
flattened (left, bilateral, or right) and the
length of the cranial base and face. The cranial base and face were shorter in association with ipsilateral flattening and they were
of equal length when there was bilateral flattening of the occipital.
The effect of unintentional cranial vault
modification on cranial morphology is of direct relevance to biological distance studies.
Numerous studies have used metric traits in
a n attempt to assess the degree of biological
distance between prehistoric or protohistoric
Indian groups within the United States
based on cranial dimensions (Corruccini,
1972; Buikstra et al., 1990; El-Najjar, 1978;
Droessler, 1981; Sciulli and Schneider, 1985;
ASYMMETRIC VAULT MODIFICATION
Sciulli, 1990).The practice of cradleboarding
was particularly widespread throughout the
Southwest, though the practice differed by
population or by degree within a population
(Hrdlicka, 1935; Stewart, 1937; Reed, 1949).
The inclusion of dimensions which are a€fected by artificial modification may produce
distorted estimates of biological distance between populations (Droessler, 1981).
In this paper we test whether cradleboarding, which resulted in cranial modification
among Hopi, had a significant effect on
morphology of the cranial base and face. I n
particular, we use finite element scaling to
measure the effects of deformation on the
differences in landmark locations. This is
accomplished by comparing averages of unmodified Hopi with Hopi for whom occipital
flattening has occurred on either the left
side, the right side, or bilaterally. In addition, we evaluate whether or not there is significant asymmetry in cranial morphology.
MATERIALS AND METHODS
Samples
The sample included in this study is
housed a t the Field Museum of Natural History in Chicago, Illinois. All individuals in
the sample were excavated from the site of
Kuchaptavela, also known a s Old Walpi or
Ash Hill, by C. L. Owen in 1901. The associated ceramics and ethnohistoric accounts
date the site to between 1300 and 1680 A.D.
Some of the Hopi from this site practiced
cradleboarding of their infants, and the sample includes both individuals with nonmodified crania and individuals with modified
crania. The inclusion of both nonmodified
and modified individuals from the same series provides a control for interpopulation
variation in craniofacial morphology (Cheverud and Midkiff, 1992; Cheverud et al.,
1992; Kohn et al., 1993).
Adult crania from the Old Walpi series
were scored a s “not modified” (or nonmodified, nm) if there was no visible evidence
of modification, “slightly modified (sm) if
there was a n indication of asymmetry present, and “modified” (m) if the lambdoid region was flattened. Intra- and interobserver
reliability for scoring modification was found
to be high in this series (Konigsberg et al.,
175
1993). The Hopi series includes 43 adult females (14 nm, 14 sm, 15 m) and 39 adult
males (9 nm, 15 sm, 15 m). The modified
crania were classified a s exhibiting either
bilateral flattening (15 females, 9 male),
flattening on the right side (5 females, 11
males), or flattening on the left side (9 females, 10 males). Gender identity was based
on museum records and visual inspection of
secondary skeletal characteristics. Age was
assessed by museum records, dental morphology, and state (open or closed) of the
sphenoccipital synchondrosis.
The lambdoid flattening observed in the
Hopi was a coincidental result of the practice
of keeping their infants in a cradle. Hopi
cradles were made of either woven saplings
or a board, and infants were bound to the
cradle for 20 hours or more per day from
birth until roughly 6 to 12 months (Dennis,
1940). The cradle provided a place for the
infant to sleep and was thought to help the
infant grow straight (Hough, 1918; Dennis,
1940). Asymmetry in lambdoid flattening
(bilateral, left, or right flattening) was produced by a n infant’s preferred head position
while sleeping (Hrdlicka, 1935).
Sample classification
Discriminant function analysis was used
to evaluate the relationship between linear
dimensions between landmarks on the cranial vault (landmarks listed in Table 1)and
our classification system. Results of discriminant function analysis indicated that nonmodified and modified crania could be reliably discriminated ( P c 0.05). Discriminant
function analysis was also used to test
whether the slightly modified crania could
be reliably re-classified into the nonmodified
or modified groups. Since the slightly modified individuals were not included in the
original classification test, this is a n unbiased test of their classification. All of the
slightly modified individuals could be reliably included within either nonmodified or
modified. The final sample includes 43 nonmodified individuals (23 females, 20 males),
16 bilaterally modified individuals (13 females, 3 males), 10 left modified individuals
(2 females, 8 males), and 13 right modified
individuals (5 females, and 8 males).
176
L.A.P. KOHN ET AL.
Measurements
T m L E 1. Landmarks recorded for the HOD&
crania
Landmarks
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
Intradentale superior
Premaxilla [(R) anterior alveolar ridge between the
canine and premolar]
Premaxilla (L)
Posterior nasal spine
Nasale
Zygomaxillare superior (R)
Zygomaxillare superior (L)
Zygomaxillare inferior (R)
Zygomaxillare inferior (L)
Infratemporal crest (R)
Infratemporal crest (L)
Vomer spine
Nasion
Frontomalare (R)
Frontomalare (L)
Pterion (R)
Pterion (L)
Optic foramen (R)
Optic foramen (L)
Bregma
Bregma-nasion (point halfway along bregma-nasion
arc)
Bregma-Pterion [(R), point halfway along bregmapterion arcl
Bregma-Pterion (L)
Lambda
Asterion (R)
Asterion (L)
Bregma-lambda (point halfway along bregmalambda arc)
Bregma-asterion [(R), point halfway along bregmaasterion arcl
Bregma-asterion (L)
Pterion-asterion [(R), point halfway along pterionasterion arcl
Pterion-asterion (L)
Pterion-lambda [(R), point halfway along pterionlambda arcl
Pterion-lambda (L)
Lambda-asterion [(R), point halfway along lambdaasterion arcl
Lambda-asterion (L)
Opisthion
Basion
Lambda-opisthion (point halfway along lambdaopisthion arcl
External auditory meatus (R)
External auditory meatus (L)
Temporo-sphenoid (R)
Temporo-sphenoid (L)
Jugular process (R)
Jugular process (L)
Foramen lacerum (R)
Foramen lacerum (L)
Anterior nasal spine
Maxillary tuberosity (R)
Maxillary tuberosity (L)
Zygomatic arch (R)
Zygomatic arch (L)
Optic foramen midpoint (average of 18 and 19)
Pterion-asterion midpoint (average of 30 and 31)
The measurements are comparable to
those presented in Kohn e t al. (1993) and
Cheverud et al. (19921, and will be briefly
discussed here. A diagraph was used to collect the three-dimensional coordinates of 53
landmarks (Fig. 1, Table 1)from the 82 Hopi
crania, and all data was collected by one
individual. The X- and Y-coordinates of the
landmarks were entered using a Tektronix 2dimensional digitizer, and the Z-coordinates
were entered by computer keyboard. After
data entry, the cranial coordinates were reoriented such that the origin was located at
anterior nasal spine. The axes were arbitrarily defined as: (1)anterior-posterior axis
was oriented along the line through anterior
nasal spine and lambda; (2) medial-lateral
axis was oriented roughly along a line connecting the right and left external auditory
meatus, perpendicular to the first axis; (3)
a superior-inferior axis was oriented roughly
along a line through bregma and opisthion,
perpendicular to the two previously defined
axes. This definition of arbitrary axes was
useful for screening data for outliers, provided a useful manner of referring to directions, and did not affect further analyses or
their interpretation.
Finite element scaling was used to measure the morphological difference between
the nonmodified crania and each type of
asymmetrically modified crania (bilateral,
left, and right modified). Finite element scaling measures the difference between two
forms, a reference (initial) and a target (subsequent) form (Lewis et al., 1980; Cheverud
et al., 1983; Cheverud and Richtsmeier 1986;
Richtsmeier and Cheverud, 1986; Richtsmeier e t al., 1992; Moss e t al., 1985; Moss,
1988; Lozanoff and Diewert, 1986;
Bookstein, 1978, 1983, 1984, 1987). The finite element scaling analyses were performed using SCAL3D (Hammer and Bachrach, 19861, and graphical representations
of the deformations are provided by FIESCA
(Morris, 1989). Alternative morphometric
methods are presented in Lele (1991), Lele
and Richtsmeier (1991, 1992), Bookstein
(19911, Goodall (19911, Kendall(1984), Mardia and Dryden (1989a,b), and reviewed by
177
ASYMMETRIC VAULT MODIFICATION
A
31
24
Fig. 1. The landmarks listed in Table 1are identified
by number. The nine finite elements listed in Table 2
representing the right and left anterior and posterior
cranial vault, the upper and lower face, and the cranial
base are depicted by connecting the appropriate landmarks with lines. A: View of the cranium from the bottom; B: Lateral view of the cranium. Note that landmarks which are not included in finite elements were
not analyzed. Only landmarks and elements from the
left side of the cranium are represented in the lateral
view since compliments on the right side would appear
superimposed in this figure. Superimposition occurs
with lateral and midline landmarks 43 and 44, 45 and
46,30,31, and 53,and 16 and 17, since the cranial base
element shown in this lateral view includes landmarks
from both the right and left sides.
Richtsmeier and coworkers (19921, Rohlf
and Marcus (19931, and Bookstein (1991).
Lateral and basal views of the average
nonmodified and average modified (bilateral, right, and left) Hopi are illustrated in
Figures 3, 5 and 7 as superimposed after
generalized procrustes rotation (Goodall and
Bose, 1987).Generalized procrustes rotation
minimizes the squared differences between
homologous landmarks in the superimposed
forms. This allows the direct visual comparison of the average forms and may be useful
to the reader in interpretation of the finite
element scaling results.
Finite element scaling is a geometric analysis of deformation, and is based on landmark Cartesian coordinates. Finite elements
are formed on each cranium by connecting
nodes or landmarks with straight lines, and
individual anatomic regions are depicted by
178
L.A.P. KOHN ET AL.
FORM
=
ASIZE
+
ASHAPE
P1
A SIZE ONLY
P1
PI
ASHAPE ONLY
P1
Fig. 2. The form strain tensor can be graphically
represented by an ellipse. The ellipse represents the
local size and shape change of a region surrounding a
landmark when comparing a reference to a target form.
The tensor describes the degree to which a standard
circle changes size (increase or decrease) and is deformed
into an ellipse in the deformation of the reference to a
target form. P1 and P2 represent the principal axes
of deformation in two dimensions. The second figure
represents a transformation of size change only, with
size change along all anatomical axes increasing the
same amount. The third figure represents a transformation of shape only, with no change in area despite the
increase along some anatomical axes and decrease along
other anatomical axes.
a finite element. In three-dimensions the
finite elements may be defined by four
(tetrahedral), five (pyramidal), six (wedgeshaped), or eight (hexahedral) landmarks.
In this analysis, thirty-six landmarks are
used to define nine hexahedral finite elements, delineating the upper and lower face
and vault on both the right and left sides,
and the cranial base (Fig. 1,Table 2).
The finite element scaling analysis of the
difference between two forms produces a form
(or Lagrangian) strain tensor (Cheverud and
Richtsmeier, 1986; Richtsmeier and Cheverud, 1986)for each landmark included in the
analysis. The form strain tensor is a symmetric matrix which provides a measure of the
difference between the reference and target
forms in the X, Y, and Z dimensions. A spectral decomposition of the form strain tensor
for each node yields the eigenvalues or principal values (ei),and eigenvectors or principal
vectors (Pi)of the matrix. The principal val-
ASYMMETRIC VAULT MODIFICATION
TABLE 2. Finite elements used in the analysis of the
effects o f annular on Houi crania'
Finite element
Landmarks
Lower face (R)
Lower face (L)
Upper face (R)
Upper face (L)
Cranial base
Posterior vault (R)
Posterior vault (L)
Anterior vault (R)
Anterior vault (L)
1, 2, 4, 5, 6, 10, 12, 48
1, 3, 4, 5, 7, 11, 12, 49
5, 6, 10, 12, 13, 14, 16, 52
5, 7, 11, 12, 13, 15, 17, 52
16, 17, 30, 31, 43, 44, 45, 46
24, 25, 28, 30, 36, 38, 43, 53
24, 26, 29, 31, 36, 38, 44, 53
16, 20, 22, 24, 25, 27, 28, 53
17, 20, 23, 24, 26, 27, 29. 53
'Landmarks are defined in Table 1
ues describe the magnitude of the most positive, intermediate, and least positive change
necessary to deform the initial into the target
form. The principal vectors describe the direction along which this form change occurs,
and are described with reference to the initial
form and along the axes described previously.
Form change can be decomposed into size
change (either increase or decrease) and
shape change (Fig. 21, and these can be calculated from the principal values. In two dimensions, if one considers a circle of standard size at each landmark in the reference
form, size change measures the degree to
which the circle increases or decreases in
area when the reference form is deformed
into the target form. Size change, s, is defined a s the average of the principal values
once they are transformed to additive scale
by the equation: li = ln[(l + 2ei)liz].The antilog of li is the proportional change in length
along the ith anatomical dimension. Shape
change, t, is a measure of the degree to which
the standard circle is deformed into a n ellipse during the deformation of the reference
into the target form. Shape change is the
standard deviation of the principal values
once they have been transformed to linear
scale. Global size change is the local size
change averaged over all landmarks, and
global shape change is the standard deviation of local size change measured a t each
landmark (Cheverud and Richtsmeier, 1986;
Richtsmeier and Cheverud, 1986).
Statistical tests
Multivariate analysis of variance of chords
(linear distances between cranial vault landmarks) and arcs (surface distance between
cranial vault landmarks) was used to test
whether unintentional cranial vault modifi-
179
cation showed a significant effect of sex,
modification, and a n interaction of sex and
modification. The lack of a significant interaction between sex and modification indicates the absence of differences in the response of male and female cranial vaults to
the effects of cradleboarding. Consequently,
data from males and females can be pooled
to explore the skeletal effects of unintentional modification.
For each type of modification (left, bilateral, and right) we test the hypothesis that
there is no significant difference between the
average nonmodified and average modified
Hopi. That is, we test whether the nonmodified and modified individuals could be drawn
from the same nonmodified sample based
on measures of form differences supplied by
finite element scaling. For each test, a
weighted average of nonmodified individuals was calculated using the sex ratio observed in the modified group. Within each
modification type, the weighted nonmodified
average was deformed into the modified average. A parametric test of significance is
not possible due to the sample size. Therefore, the significance of the observed differences between nonmodified and modified
averages is tested by a nonparametric bootstrap procedure suggested by Lele and Richtsmeier (1991) and used in Cheverud et al.
(1992) and Kohn et al. (1993). To perform
this test, two bootstrap samples, one nonmodified and one modified, are generated by
random sampling with replacement of the
nonmodified sample. The random sampling
is stratified by sex, such that males and females are drawn from nonmodified sample
in the sex ratio observed in the modified sample. The bootstrap nonmodified average is
deformed into the bootstrap modified average. Five hundred bootstrap sample pairs
were generated for these significance tests.
The statistical significance of the observed
difference between nonmodified and modified averages is measured by the proportion
of the bootstrap differences which exceed
those actually observed between the groups.
This procedure is used to test local size and
shape change at each landmark, global size
and shape change, and volume differences
between nonmodified and modified individuals. The evaluation of local and global size
change and volume differences are two-
180
L.A.P. KOHN ET AL.
A
Y
L
X
B
2
L
X
Fig. 3. Superimposition of an average nonmodified
Hopi (solid line) and average bilaterally modified Hopi
(dotted line) after Procrustes registration on all landmarks. Unconnected landmarks were not included in
the present analysis. A: Basal view of skull; B: Right
side of skull, seen as though viewed from the left through
a transparent left side of the skull; C: Left side of skull.
ASYMMETRIC VAULT MODIFICATION
181
A
Y
L
X
B
Z
L,
C
Fig. 4. Finite element scaling results of the deformation of the average nonmodified Hopi into the average
bilaterally modified Hopi drawn on the average nonmodified Hopi. The ellipses represent the magnitudes and
directions of difference between the average nonmodified and bilaterally modified Hopi. Ellipses are exagger-
ated by a factor of 2.5 to aid in interpretation. Unconnected landmarks were not included in the present analysis.
A: Basal view of skull; B: Right side of skull, seen as
though viewed from the left through a transparent left
side of the skull; C: Left side of skull.
182
L.A.P. KOHN ET AL
TABLE 3. Results
of finite element scaling analyses of nonmodified into bilaterally modified Hopi crania'
Landmark
Cranial vault
Bregma
Bregma-lambda
Lambda
Opisthion-lambda
Opisthion
Pterion-asterion midpt.
Pterion (R)
Pterion (L)
Bregma-pterion (R)
Bregma-pterion (L)
Bregma-asterion (R)
Bregma-asterion (L)
Pterion-asterion (R)
Pterion-asterion (L)
Asterion (R)
Asterion (L)
Cranial base
Jugular process (R)
Jugular process (L)
Foramen lacerum (R)
Foramen lacerum (L)
Optic foramen midpt.
Vomer spine
Infratemporal crest (R)
Infratemporal crest (Ll
Face
Fronto-malare (R)
Fronto-malare (L)
Zygomaxillare superior (R)
Zygomaxillare superior (L)
Nasion
Nasale
Infradentale superior
Posterior nasal spine
Maxillary tuber (R)
Maxillary tuber (L)
Premaxilla-maxilla (R)
Premaxilla-maxilla (L)
Global
Element volume
Lower face (R)
Lower face (L)
Upper face (RI
Upper face (L)
Cranial base
Posterior cranial vault (RI
Posterior cranial vault (L)
Anterior cranial vault (R)
Anterior cranial vault (L)
Size (Prob)
Shape (Prob)
PV1 (DIR)
0.57 (0.282)
-0.66 (0.598)
-3.73 (0.999)"
-4.77 (0.962)'x'k
-2.06 (0.958)**
-0.97 (0.900)
1.91 (0.024)"
1.70 (0.048)"'
3.64 (0.004)*
4.47 (0.001)"
2.17 (0.048)*
2.65 (0.054)
4.59 (0.006)*
3.62 (0.008)'
-1.03 (0.800)
0.82 (0.254)
5.25 (0.0011'
5.46 (0.0141"
7.02 (0.001)"
7.39 (0.008)'
6.95 (0.001)'
7.51 (0.001)'
3.59 (0.001)'
3.14 (0.056)"*
4.18 (0.022)*
3.20 (0.1141
9.82 (O.OO1)'L
6.88 (0.028)*
7.96 (0.002)'
5.46 (0.042)*
6.85 (0.001)"
6.76 (0.002)"
-4.82 (0.998)*
-0.65 (0.632)
2.69 (0.188)
1.46 (0.340)
2.65 (0.044)""
2.19 (0.034)**
3.13 (0.074)
0.07 (0.5101
-3.70 (0.986)*
1.06 (0.352)
-1.40 (0.828)
-1.98 (0.7401
1.08 (0.264)
0.18 (0.470)
-1.40 (0.880)
3.38 (0.082)
-2.60 (0.874)
3.80 (0.086)
-0.64 (0.678)
-2.99 (0.964)""
0.40 (0.274)
PV2 (DIR)
PV3 (DIR)
4.86 (M-L)
5.45 (AS-PI)
2.04 (M-L)
1.56 (M-L)
4.54 (AI-PS)
6.08 (M-L)
6.24 (M-L)
5.37 (M-L)
10.05 (AS-PI1
9.47 (AS-PI1
17.75 (A-PI
12.47 (A-P)
17.03 (A-P)
11.14 (M-L)
6.09 (A-P)
6.84 (M-L)
4.07 (S-I)
0.80 (M-L)
0.44 (AI-PS)
-0.71 (AI-PSI
1.21 (M-L)
2.89 (S-I)
2.75 (S-I)
2.53 (S-I)
2.76 (AI-PSI
3.94 (AI-PSI
-0.17 (S-I)
2.62 (S-I)
4.09 (M-L)
4.26 (A-P)
1.60 (AMI-PLS)
4.98 (AI-PSI
-6.39 (A-P)
-7.35 (AI-PSI
- 11.92 (AS-PI)
-13.06 (AS-PI)
-10.45 (AS-PI)
- 10.24 (A-P)
-2.74 (A-P)
-2.41 (A-P)
-0.93 (M-L)
0.94 (M-L)
-7.83 (M-L)
-5.41 (M-L)
-4.58 (S-I)
-3.19 (S-I)
-9.40 (ALI-PMS)
-7.98 (AS-PI)
6.20 (0.0081"
4.39 (0.210)
9.51 (0.340)
7.56 (0.482)
4.81 (0.058)'*
2.58 (0.250)
3.94 (0.460)
3.32 (0.566)
1.72 (MI-LS)
5.45 (MI-LS)
15.32 (AI-PSI
11.22 (M-L)
9.57 (M-L)
6.01 (RI-0s)
9.43 (M-L)
2.85 (M-L)
-2.91 (A-P)
-1.67 (A-P)
4.65 (M-L)
2.62 (S-I)
2.25 (S-I)
1.40 (A-P)
1.18 (S-I)
2.08 (S-I)
- 11.57
6.11 (0.096)'"
4.54 (0.4261
3.75 (0.352)
3.24 (0.668)
2.53 (0.652)
1.55 (0.7001
2.07 (0.386)
7.34 (0.421)
3.90 (0.406)
6.95 (0.182)
4.24 (0.086)**
4.93 (0.016)"
1.89 (S-I)
5.28 (AMS-PLI)
2.08 (S-I)
0.64 (S-I)
4.77 (S-I)
1.73 (S-I)
0.64 (AS-PI)
14.80 (RI-OS)
1.98 (AMI-PLS)
14.79 (M-L)
4.17 (S-I)
2.72 (A-P)
-0.74 (A-P)
- 10.84 (M-L)
3.59 (AMI-PLS) -5.03 (AM-PL)
0.39 (A-P)
-6.20 (M-L)
-0.04 (M-L)
-6.13 (A-P)
- 1.35 (M-LI
0.04 (A-P)
0.80 (A-P)
-1.91 (M-L)
-0.59 (AI-PSI
-4.06 (M-L)
2.10 (A-P)
-4.65 (RS-01)
-2.11 (ALS-PMI)
-7.04 (M-L)
2.38 (S-I)
-3.74 (A-P)
0.32 (A-P)
-5.87 (M-L)
-2.20 (S-I1
-8.54 (M-L)
-5.13
-8.84
-7.64
-2.91
-0.49
-0.40
-4.40
(MS-LI)
(MS-LI)
(AS-PI)
(A-P)
(A-P)
(RS-01)
(A-P)
(A-P)
2.64 (0.012)'
0.0006 (0.462)
0.0090 (0.390)
0.0336 (0.132)
0.0359 (0.120)
0.0321 (0.162)
-0.0619 (0.978)*
-0.0311 (0.850)
0.0011 (0.458)
0.0254 (0.142)
'Reported results include size and t h e proportion of bootstrap samples exhibiting a greater size difference than that observed In the samples;
shape and the proportion of bootstrap samples exhibiting a greater shape difference than t h a t observed in the samples; the principal values
(PVi) and their associate anatomical directions (transverse directions for midsagittal landmarks are indicated a s 0 for left and R for right);
and the proportional volume differences between nonmodified and bilaterally modified Hopi for each finite element, and the proportion of
bootstrap samples exhibiting greater volume differences. Tests of local and global size and element volume are two-tailed tests. Landmarks or
elements with proportions greater than 0.975 are significantly smaller than nonmodified, and proportions smaller than 0.025 are significantly
larger than nonmodified. Tests of local and global shape change are one-tailed tests, and proportmns greater than 0.05 are significantly different
from nonmodified
*Statistical significance a t P = 0.05 level.
**Statistical significance at P = 0.10 level.
sided tests, with probabilities less than 0.025
and greater than 0.975 significant at the 5%
level. Local and global shape changes are
one-sided tests, and probabilities less than
0.05 indicate significance at the 5% level of
significance. Direction of local shape differences are uninterpretable in the absence of
significant local shape change (Bookstein,
ASYMMETRIC VAULT MODIFICATION
183
A
B
2
L x
Fig. 5. Superimposition of an average nonmodified
Hopi (solid line) and average right modified Hopi (dotted
line) after Procrustes registration on all landmarks. Unconnected landmarks were not included in the present
analysis. A Basal view of skull; B: Right side of skull,
seen as though viewed from the left through a transparent left side of the skull; C: Left side of skull.
184
L.A.P. KOHN ET AL.
A
Fig. 6. Finite element scaling results ofthe deformation of the average nonmodified Hopi into the average
right modified Hopi drawn on the average nonmodified
Hopi. The ellipses represent the magnitudes and directions of difference between the average nonmodified and
right modified Hopi. Ellipses are exaggerated by a factor
-
of 2.5 to aid in interpretation. Unconnected landmarks
were not included in the present analysis. A: Basal view
of skull; B: Right side of skull, seen as though viewed
from the left through a transparent left side of the skull;
C: Left side of skull.
185
ASYMMETRIC VAULT MODIFICATION
TABLE 4. Results
Landmark
Cranial vault
Bregma
Bregma-lambda
Lambda
Opisthion-lambda
Opisthion
Pterion-asterion midpt.
Pterion (R)
Pterion (L)
Bregma-pterion (R)
Bregma-pterion (L)
Bregma-asterion (R)
Bregma-asterion (L)
Rerion-asterion (R)
Pterion-asterion (L)
Asterion (R)
Asterion (L)
Cranial base
Jugular process tR)
Jugular process (L)
Foramen lacerum (R)
Foramen lacerum (L)
Optic foramen midpt.
Vomer spine
Infratemporal crest (R)
Infratemporal crest (L)
Face
Fronto-malare (R)
Fronto-malare (L)
Zygomaxillare superior (R)
Zygomaxillare superior (L)
Nasion
Nasale
Infradentale superior
Posterior nasal spine
Maxillary tuber. (R)
Maxillary tuber. (L)
Premaxilla-maxilla (R)
Premaxilla-maxilla (L)
Global
Element volume
Lower face (R)
Lower face (L)
Upper face (R)
Upper face (L)
Cranial base
Posterior cranial vault (R)
Posterior cranial vault (L)
Anterior cranial vault (R)
Anterior cranial vault (Ll
of
finite element scaling analyses of nonmodified into right modified Hopi crania'
Size (Prob)
Shape (Prob)
PV1 (DIR)
-0.32 (0.600)
-3.32 (0.912)
-1.38 (0.826)
0.76 (0.418)
0.28 (0.430)
0.33 (0.400)
2.11 (0.052)
1.83 (0.084)
1.82 (0.138)
-0.67 (0.642)
-5.44 (1.000)*
2.32 (0.068)
3.52 (0.008)"
0.46 (0.388)
-3.88 (0.998)*
1.88 (0.086)
2.60 (0.118)
3.93 (0.232)
3.21 (0.010)*
1.85 (0.8601
2.53 (0.510)
3.71 (0.012)*
3.91 (0.001)*
3.59 (0.142)
6.86 (0.002)*
4.54 (0.066)**
10.00 (0.001)*
7.14 (0.010)*
8.59 (0.001)"
2.29 (0.770)
6.11 (0.001)"
5.89 (0.004)"
2.23 (S-I)
1.57 (AOI-PRS)
2.41 (S-I)
3.48 (S-I)
3.12 (AI-PS)
3.51 (M-L)
6.95 (A-P)
6.48 (M-L)
10.52 (A-P)
5.55 (S-I)
5.59 (A-PI
12.61 (MSILI)
14.80 (ALS-PMI)
3.18 (M-L)
4.02 (A-P)
10.46 (M-L)
0.77 (M-L)
-3.76 (A-P)
-3.30 (AOS-PRI) -7.47 (M-L)
-0.98 (M-L)
- 5.20 (A-P)
-0.28 (A-P)
-0.79 (M-L)
0.90 (M-L)
-2.98 (AS-PI)
2.56 (S-I)
-4.66 (A-P)
2.88 (M-L)
-2.90 (S-I)
2.14 (S-I)
-2.62 (A-P)
3.13 (S-I)
-6.64 (M-L)
- 1.49 (A-P)
-5.45 (M-L)
-2.76 IS-I)
-15.65 (M-L)
1.99 (A-P)
-5.87 (MI-LS)
5.72 (AI-PS)
-7.23 (AMS-PLI)
0.82 (A-P)
-2.44 (S-I)
-9.94 (M-L)
-4.23 (S-I)
0.98 (A-P)
-4.61 (S-I)
0.92 (0.372)
0.83 (0.328)
0.68 (0.426)
4.09 (0.136)
-0.24 (0.618)
0.91 (0.280)
3.71 (0.066)
0.23 (0.474)
7.82 (0.010)*
4.45 (0.332)
4.61 (0.858)
12.93 (0.194)
4.09 (0.148)
3.61 (0.054)**
6.24 (0.088)*"
2.55 (0.836)
10.60 (AL-PM)
7.20 (AI-PSI
7.19 (S-I)
26.72 (A-PI
5.30 (M-L)
4.19 (M-L)
12.94 (M-L)
3.06 (AM-PL)
2.54 (AM-PL)
-0.24 (AS-PI)
-0.19 (A-P)
0.52 (S-I)
-0.84 (A-PJ
2.94 (S-I)
3.50 (S-I)
0.90 (S-I)
-8.52
-3.85
-4.29
-8.78
-4.69
-3.99
-3.62
-3.07
(S-I)
(M-L)
(M-L)
(M-L)
(S-I)
(A-P)
(A-P)
(AL-PM)
0.51 (M-L)
5.24 (AI-PS)
-2.59 (A-P)
-0.56 (A-P)
-1.39 (M-L)
-0.98 (M-L)
0.67 (AS-PI)
1.41 (A-P)
-4.11
-7.27
-6.82
-4.74
-3.15
-3.81
-2.23
-2.26
-3.51
-5.86
-3.73
-4.82
(S-I)
(M-L)
(M-L)
(M-L)
(A-P)
(A-P)
-0.19 (0.522)
1.55 (0.442)
-2.12 (0.888)
-0.19 (0.548)
0.17 (0.448)
-0.41 (0.660)
1.35 (0.194)
5.88 (0.012)*
0.59 (0.356)
0.70 (0.420)
0.88 (0.322)
-0.48 (0.614)
0.53 (0.306)
3.32 (A-P)
3.10 (0.780)
8.13 (AS-PI)
6.73 (0.612)
4.50 (0.292)
3.78 (S-I)
4.07 (0.660)
5.22 (S-I)
3.62 (0.478)
5.45 IS-I)
3.17 (0.132)
3.88 (S-I)
3.28 (0.050)**
6.00 (AI-PSI
9.09 (0.184)
22.46 6-11
3.70 (0.560)
5.72 (MI-LS)
5.32 (0.498)
7.18 (M-L)
3.96 (0.222)
6.16 (S-I)
3.99 (0.248)
4.88 (A-P)
PV2 (DIR)
0.00 (A-P)
1.66 (A-P)
0.70 (A-P)
-1.03 (S-I)
PV3 (DIR)
(M-L)
(M-L)
(MS-LI)
(S-I)
(M-L)
(M-L)
2.14 (0.452)
0.0471 (0.104)
0.0241 (0.324)
0.0028 (0.512)
0.0130 (0.426)
0.0820 (0.036)**
-0,0565 (0.926)
0.0345 (0.196)
-0.0467 (0.882)
0.0019 (0.498)
'Reported results include size and the proportion of bootstrap samples exhibiting a greater size difference than that observed in t h e samples;
shape and the proportion of bootstrap samples exhibiting a greater shape difference than that observed in t h e samples; the principal values
(PVi) and their associate anatomical directions (transverse directions for midsapttal landmarks are indicated as 0 for left and R for right);
and the proportional volume differences between nonmodified and right modified Hopi for each finite element, and the proportion of bootstrap
samples exhibiting greater volume differences, Tests of local and global size and element volume are two-tailed tests. Landmarks or elements
with proportions greater than 0.975 are significantly smaller than nonmodified, and proportions smaller t h a n 0.025 are significantly larger
than nonmodified. Tests of local and global shape change are one-tailed tests, and proportions greater than 0.05 are significantly different
from nonmodified.
*Statistical significance a t P = 0.05 level.
**Statistical significance at P = 0.10 level.
1984; Cheverud et al., 1992), since lack of
significance indicates that there are no statistical size differences among anatomical
dimensions.
Following the methods of Bjork and Bjork
(1964) we also evaluate whether there is significant asymmetry in size and shape
change. That is, we test for a significant as-
186
L.A.P. KOHN ET AL
A
B
C
2
I
Fig. 7. Superimposition of an average nonmodified
Hopi (solid line) and average left modified Hopi (dotted
line) after Procrustes registration on all landmarks. Unconnected landmarks were not included in the present
analysis. A: Basal view of skull; B: Right side of skull,
seen as though viewed from the left through a transparent left side of the skull; C: Left side of skull.
ASYMMETRIC VAULT MODIFICATION
187
A
Y
L
X
B
Fig. 8. Finite element scaling results ofthe deformation of the average nonmodified Hopi into the average
left modified Hopi drawn on the average nonmodified
Hopi. The ellipses represent the magnitudes and directions of difference between the average nonmodified and
left modified Hopi. Ellipses are exaggerated by a factor
of 2.5 to aid in interpretation. Unconnected landmarks
were not included in the present analysis. A Basal view
of skull; B: Right side of skull, seen as though viewed
from the left through a transparent left side of the skull;
C: Left side of skull.
188
L.A.P. KOHN ET AL.
TABLE 5. Results o f finite element scaling analvses o f nonmodified into left modified HoDi crania'
Landmark
Cranial vault
Bregma
Bregma-lambda
Lambda
Opisthion-lambda
Opisthion
Pterion-asterion midpt.
Pterion (R)
Pterion (L)
Bregma-pterion (R)
Bregma-pterion (L)
Bregma-asterion (R)
Bregma-asterion (L)
Pterion-asterion (R)
Pterion-asterion (L)
Asterion (R)
Asterion (L)
Cranial base
Jugular process (R)
Jugular process (L)
Foramen lacerum (R)
Foramen lacerum (L)
Optic foramen midpt.
Vomer spine
Infratemporal crest (R)
Infratemporal crest (L)
Face
Fronto-malare (R)
Fronto-malare (L)
Zygomaxillare superior (R)
Zygomaxillare superior (L)
Nasion
Nasale
Infradentale superior
Posterior nasal spine
Maxillary tuber. (R)
Maxillary tuber. (L)
Premaxilla-maxilla (R)
Premaxilla-maxilla (L)
Global
Element volume
Lower face (R)
Lower face (L)
Upper face (R)
Upper face (L)
Cranial base
Posterior cranial vault (R)
Posterior cranial vault (L)
Anterior cranial vault (R)
Anterior cranial vault (L)
Size (Prob)
Shape (Prob)
PV1 (DIR)
0.05 (0.536)
-1.55 (0.756)
- 1.64 (0.840)
0.60 (0.416)
1.66 (0.188)
0.39 (0.398)
3.00 (0.028)""
2.94 (0.026)**
-2.08 (0.832)
1.33 (0.282)
-0.33 (0.588)
-2.63 (0.972)""
0.15 (0.470)
1.66 (0.204)
0.51 (0.386)
-2.05 (0.918)
3.18 (0.076)""
3.16 (S-I)
3.06 (0.582)
2.82 (S-I)
3.69 (0.006)"
2.42 (S-I)
3.11 (0.488)
4.48 (AI-PS)
5.88 (0.024)" 10.16 (S-I)
5.39 (0.001)"
5.99 (S-I)
2.32 (0.200)
5.21 (S-I)
2.28 (0.724)
5.57 (S-I)
6.36 (0.002)"
6.34 (S-I)
4.23 (AL-PM)
2.04 (0.802)
5.79 (0.016)"
7.91 (MS-LI)
6.35 (0.052)"" 2.60 (AI-PSI
5.90 (0.052)"" 6.82 (S-I)
4.46 (0.336)
6.52 (AL-PM)
4.69 (0.014)"
7.29 (MS-LI)
4.18 (0.086)** 2.67 (A-P)
4.17 (0.058)
-1.84 (0.734)
7.51 (0.048)**
3.33 (0.226)
4.13 (0.004)"
0.22 (0.454)
0.84 (0.412)
-0.57 (0.600)
4.88 (0.304)
5.80 (0.220)
7.49 (0.722)
4.17 (0.928)
5.70 (0.036)"
2.09 (0.478)
4.33 (0.418)
3.63 (0.606)
1.13 (0.274)
0.45 (0.562)
0.36 (0.434)
0.23 (0.492)
-0.58 (0.594)
0.23 (0.434)
-2.08 (0.896)
- 1.67 (0.790)
2.00 (0.234)
- 1.99 (0.648)
-3.20 (0.946)
- 1.64 (0.780)
0.36 (0.370)
11.55 (ALI-PMS)
3.71 (AI-PS)
21.28 (A-P)
9.46 (AL-PM)
13.09 (A-P)
2.09 (M-L)
5.84 (S-I)
3.09 (S-I1
10.38 (0.048)" 13.67 (A-P)
10.66 (0.542)
16.02 (S-I)
5.29 (0.158)
4.82 (MS-LI)
5.39 (0.484)
7.87 6-1)
2.83 (0.790)
3.45 (A-P)
2.47 (0.424)
3.22 (M-L)
3.14 (0.126)
1.08 (S-I)
8.48 (0.228)
9.49 (M-L)
7.44 (0.086)** 13.73 (MS-LI)
3.03 (0.922)
1.76 (M-L)
6.77 (0.010)*
3.08 (A-P)
3.29 (0.536)
2.85 (S-I)
2.26 (0.474)
PV2 (DIR)
1.44 (M-L)
-3.11 (M-L)
-0.73 (M-L)
0.82 (M-L)
0.80 (M-L)
2.59 (M-L)
4.48 (M-L)
3.82 (M-L)
-2.58 (A-P)
0.77 (AM-PL)
-1.65 (A-P)
1.16 (AS-PI)
1.86 (M-L)
3.39 (S-I)
-0.83 (A-P)
-1.20 (MS-LI)
3.78 (AMS-PLI)
0.80 (M-L)
5.07 (M-L)
2.92 (S-I)
3.02 (M-L)
1.34 (S-I)
1.97 (M-L)
0.86 (M-L)
4.28 (S-I)
-0.38 (AM-PL)
3.71 (MI-LS)
-0.85 (M-L)
-1.78 (S-I)
0.47 (S-I)
-0.94 (A-P)
-1.57 (A-P)
-0.61 (A-P)
-1.97 (A-P)
0.04 (S-I)
-2.51 (A-P)
PV3 (DIR)
-4.16 (A-P)
-4.02 (A-P)
-6.13 (A-P)
-3.21 (AS-PI)
4.82 (A-P)
-6.55 (A-P)
-0.26 (A-P)
-0.15 (A-P)
-8.71 (M-L)
-0.82 (S-I)
-6.23 (MI-LS)
-10.34 (M-L)
-7.20 (A-P)
-4.24 (AM-PL)
-4.26 (MI-LS)
-6.99 (MI-LS)
-
-1.50 (MI-LS)
-8.97 (AS-PI)
-0.03 (S-I)
1.48 (AM-PL)
-2.13 (S-I)
-2.63 (A-P)
-4.69 (A-P)
-5.25 (A-P)
-
-11.30 (M-L)
10.80 (AL-PM)
-6.61 (A-P)
-5.44 (A-P)
-3.15 (M-L)
-2.83 (A-P)
-5.97 (M-L)
-10.74 (S-I)
-5.22 (MI-LS)
-5.38 (S-I)
- 11.16 (M-L)
-4.87 (M-L)
-
-0.0140 (0.6640)
-0.0419 (0.7660)
0.0592 (0.0500)**
0.0538 (0.1480)
0.1101 (0.0180)"
0.0109 (0.4140)
-0.0361 (0.7640)
-0.0248 (0.7420)
-0,0310 (0.8240)
1 Reported results include size and the proportion of bootstrap samples exhibiting a greater size difference than that observed in th e samples;
shape and the proportion of bootstrap samples exhibiting a greater shape difference than t h a t observed in the samples; the principal values
(PVi) and their associate anatomical directions (transverse directions for midsagittal landmarks are indicated as 0 for left and R for right);
and the proportional volume differences between nonmodified and left modified Hopi for each finite element, and the proportion of bootstrap
samples exhibiting greater volume differences. Tests of local and global size and element volume are two-tailed tests. Landmarks or elements
with proportions greater than 0.975 are significantly smaller than nonmodified and proportions smaller than 0.025 are significantly larger
than nonmodified Tests of local and global shape change are one-tailed tests, and proportions greater than 0.05 are significantly different
from nonmodified.
*Statistical significance a t P = 0.05 level
**Statistical significance a t P = 0.10 level.
sociation between the amount of size or
shape change and the size of modification.
The average nonmodified male Hopi and the
average nonmodified female Hopi were esti-
mated. Finite element scaling was used to
estimate the difference between the average
nonmodified male and each modified male
by deforming the average nonmodified male
ASYMMETRIC VAULT MODIFICATION
Hopi into each modified male Hopi. The size
and shape change for each deformation was
calculated. Size asymmetry in males is the
bilateral difference (right minus left) in size
change for the deformation of the nonmodified average male into each modified male.
The comparable procedure was repeated for
females. Shape asymmetry is the bilateral
difference in shape change from the same
deformations. A Pearson product-moment
correlation tests the association between
magnitude of asymmetry and the side of
modification. Side of modification was coded
as 1 for left-sided occipital flattening, 0 for
bilateral occipital flattening, and - 1 for
right-sided occipital flattening. A positive
correlation of size (or shape) asymmetry
with side of modification indicates that individuals exhibit greater size (or shape)
change on the side that is not modified.
189
and right bregma-asterion). The bilaterally
modified cranial vault appears to be shorter
(anterior-posterior) and wider (medial-lateral). The flattening of the lambdoid region
is evidenced by a n anterior-superior to posterior-inferior decrease ( 11-14%) a t lambda,
opisthion, and opisthion-lambda. A parallel
increase ( 5 ~ 1 7 %occurs
)
a t the right and left
asterion, bregma-lambda, and bregmapterion. An anterior-posterior decrease (210%) is seen a t landmarks located along the
midsagittal plane (bregma, pterion-asterion
midpoint) and the anterior-lateral cranial
vault (right and left pterion). A marked widening (2-11%) of the cranial vault is present
a t the midsagittal landmarks as well a s bilaterally at pterion, and pterion-asterion.
There is a n anterior-posterior increase (417%) a t posterior-lateral landmarks (right
and left bregma-asterion, pterion-asterion),
and the cranial vault is wider at pterionasterion.
Little additional change in the craRESULTS
nial vault occurs along the superior-inferior
Bilateral modification
axes, with approximate 2-5% superior-infeThe average bilaterally modified Hopi fe- rior increase in the anterior and lateral cramale was 3.7% smaller in total volume than nial vault.
the average nonmodified Hopi female. The
Extensive form change in the cranial vault
total volume of the average bilaterally modi- is not accompanied by marked changes in
fied male did not differ from the average morphology of the cranial base with bilateral
nonmodified Hopi male. Prior to finite ele- modification. Compared to the nonmodified
ment scaling analysis, the modified Hopi fe- average Hopi, the average bilaterally modimales were rescaled to ensure that differ- fied Hopi has a smaller right jugular process.
ences observed between nonmodified and Size increases at optic foramen midpoint and
bilaterally modified crania were not due to vomer spine approach significance. A signifitheir differences in overall size.
cant shape change at the right jugular proThe finite element scaling results measur- cess is due to a 12% decrease along a n axis
ing the differences between the average non- from medial-superior to lateral-inferior and
modified and average bilaterally modified a 3% anterior-posterior decrease at this
Hopi are presented in Table 3 and Figure 4. landmark. Shape change a t the optic foraThere is no significant global size difference men midpoint approaches significance with
between the nonmodified and bilaterally 2-9% increases along the medial-lateral and
modified Hopi, but there is a significant superior-inferior axes and a 3% decrease
global shape difference. The volume of the along the anterior-posterior axis.
posterior cranial vault is smaller in the bilatSignificant effect of bilateral cranial vault
erally modified Hopi, with a statistically sig- modification on the Hopi face are rare: two
nificant difference on the right posterior cra- facial landmarks exhibit significant or
nial vault.
nearly significant size or shape changes.
Bilateral modification has a significant ef- There is a general trend toward a higher
fect on the size and shape of the Hopi cranial (superior-inferior), narrower (medial-latvault. The posterior cranial vault (lambda, eral) face in the modified Hopi, however, few
opisthion, opisthion-lambda) is smaller and of the landmarks exhibit significant shape
the lateral cranial vault is larger (bilaterally change. The region surrounding the right
at pterion, bregma-pterion, pterion-asterion, fronto-malare is significantly smaller, and
190
L.A.P. KOHN ET AL.
the reduced size at the left premaxilla-maxilla approaches significance. The left premaxilla-maxilla is longer (anterior-posterior), narrower (medial-lateral),and shorter
(superior-inferior) in the modified Hopi. The
bilaterally modified Hopi right fronto-malare is narrower (medial-lateral) and higher
(superior-inferior) than the landmark in the
nonmodified Hopi.
eral), and higher (superior-inferior) a t
lambda. Landmarks on the right lateral and
posterior cranial vault, including asterion,
bregma-asterion, and bregma-pterion are
longer (anterior-posterior) and narrower
(medial-lateral) and shorter (superior-inferior) than in the nonmodified cranial vault.
The only significant shape change on the left
side of the cranial vault is a t left asterion,
which exhibits a increased width (10%) and
Asymmetrical modification: right side
decreased height (5%).
The total volume of the average right modThe modification of the right cranial vault
ified Hopi is smaller than the average non- results in few statistically significant effects
modified Hopi. The average modified male on the morphology of the cranial base. There
is 2.2% smaller and the average modified are no significant localized size differences
female is 3% smaller than the average non- a t any of the landmarks. There is a signifimodified male and female, respectively. The cant shape difference only a t the right jugumodified individuals are re-scaled prior to lar process, which is longer (10%) along a n
analysis to ensure that observed differences axis from anterior-lateral to posterior-mein form are not due to differences in volume. dial, longer (2%)along a n axis from anteriorFinite element scaling results measuring medial to posterior-lateral,and shorter (8%)
the difference between the average nonmodi- superior-inferior. The decrease (3-4%) in
fied Hopi and the average right modified length, increase (4-12%) in width, and inHopi are presented in Table 4 and Figure 6. crease (3-4%) in height observed a t vomer
Neither global size nor shape differences are spine and right infratemporal crest apobserved in comparing average nonmodified proaches significance. Despite the lack of
with average right modified Hopi. The vol- significance of shape change, considerable
ume of the right anterior and posterior cra- asymmetry in magnitude of shape change
nial vault is smaller than nonmodified, but estimates are observable between the right
this difference is not significant. The volume and left sides. Since the sample size of right
of the cranial base is smaller than nonmodi- modified individuals is small, the estimates
fied, and this difference approaches signif- of shape change may be highly influenced
icance.
by a few extreme individuals.
Modification of the right side of the cranial
Modification of the right side of the cranial
vault has a significant effect on cranial vault vault also results in few statistical signifimorphology. The region surrounding right cant effects on facial morphology. There is a
bregma-asterion and right asterion are sig- significant size increase at the posterior nanificantly smaller in the right modified Hopi, sal spine. Shape change at intradentale suwhile the right pterion-asterion is signifi- perior approaches significance with a n incantly larger in the right modified Hopi. crease (6%) along a n axis from anteriorThere are a number of significant localized inferior to posterior-superior and a decrease
shape changes associated with modification (2%) in width.
of the right side of the cranial vault. The
Asymmetrical modification: left side
flattening of the right posterior cranial vault
is associated with a lengthening and widenThere was no difference in total volume
ing of the right posterior-lateral and right between the average nonmodified female
anterior-lateral cranial vault. Although not and the average left modified female. The
significant, the flattening of the right occipi- average left modified male was 2% smaller
tal appears to be associated with a n increase than the average nonmodified male, and the
in width (medial-lateral) and a n increase in coordinates of the left modified males were
height (superior-inferior) on the left side of transformed to correct this volume differthe cranial vault. The cranial vault is shorter ence prior to finite element scaling analysis.
(anterior-posterior), narrower (medial-lat- This ensures that difference between aver-
191
ASYMMETRIC VAULT MODIFICATION
TABLE 6. Pearson product-moment correlation of
asymmetry i n size and shape change with
direction of modification'
Landmarks
2, 3
6, 7
10, 11
14, 15
16, 17
22, 23
25, 26
28, 29
30,31
43,44
45,46
48,49
Size (Prob)
Shape (Prob)
-0.052 (0.776)
0.139 (0.442)
-0.194 (0.280)
0.149 (0.408)
-0.149 (0.386)
-0.353 (0.035)*
0.565 (0.001)*
0.567 (0.001)*
-0.505 (0.002)*
0.216 (0.207)
0.102 (0.554)
0.065 (0.722)
-0.043 (0.815)
-0.221 (0.216)
-0.098 (0.587)
0.277 (0.119)
0.100 (0.560)
-0.070 (0.686)
-0.016 (0.925)
-0.181 (0.291)
0.232 (0.174)
0.013 (0.939)
-0.096 (0.579)
0.321 (0.073)**
1 Asymmetry was measured as right minus left, and direction of modification was 1 for left modified individuals, 0 for bilaterally modified
individuals, and - 1 for right modified individuals.
*Statistical significance a t P = 0.05 level.
**Statistical significance at P = 0.10 level.
age nonmodified and average left modified
individuals is not due to differences in
volume.
The sample size of the left modified individuals (N = 10) is smaller than that for the
bilaterally (N = 16) or right (N = 13) modified individuals, complicating detection of
significant differences between groups.
However, the presence of trends comparable
t o those observed above can be assessed.
The finite element scaling results measuring the difference between the average nonmodified and average left modified Hopi is
presented in Table 5 and Figure 8. There is
no global size or shape difference between
the average nonmodified and average left
modified Hopi. The volume of the cranial
base is significantly larger in the average
left modified Hopi, and the larger volume of
the right upper face in the average modified
Hopi approaches significance.
The pattern of modification observed in
the left modified Hopi generally follows the
patterns observed for the bilaterally and
right modified individuals in that there are
no significant size differences between the
average forms. It should be noted that the
size increase at the right and left pterion
and the size decrease a t left bregmaasterion approach significance. Modification
of the left cranial vault results in anteriorposterior decreases at midsagittal and left
posterior-lateral landmarks of the cranial
vault. The midsagittal and left posterior cra-
nial vault decreases in width while the left
anterior cranial vault increases in width.
There is a general trend toward an increased
superior-inferior height throughout the left
side of the cranial vault. Several significant
shape changes are observable on the right
side of the cranial vault. Left modification
of the cranial vault results in an anteriorposterior decrease and a medial-lateral and
superior-inferior increase on the right side
of the cranial vault.
As was observed with right cranial vault
modification, significant effects of left modification on the morphology of the cranial
base are rare. There is a significant size increase at the optic foramen midpoint, and
the size increase at the right foramen lacerum approaches significance. The only significant difference in shape between the average nonmodified and left modified Hopi is
at the optic foramen midpoint, which is
longer (12%),wider (3%), and shorter (3%)
in the modified individuals. As was observed
with right cranial vault modification, large
and asymmetric shape change are observed
in the cranial base, especially at the jugular
processes and foramen lacerum. The small
sample representing left modified cranial
vault modification may cause extreme individuals to excessively influence the average
for modified individuals.
The face also exhibits little significant effect of left modification of the cranial vault.
There are no significant localized size differences between the average nonmodified and
left modified Hopi. The right premaxillamaxilla is longer (3%) and wider (11%)in
the left modified Hopi. Right fronto-malare
is longer (13%),narrower (12%),and higher
(4%) in the left modified Hopi. The shape
change a t the right maxillary tuberosity approaches significance. The right maxillary
tuberosity is longer (13%) along an axis
from medial-superior to lateral-inferior and
smaller (5%)along an axis from medial-inferior to lateral-superior.
Asymmetry
A Pearson product-moment correlation
measures the association of direction of modification and magnitude of asymmetry (the
difference between the right and left sides)
in size and shape change (Table 6). Apositive
192
L.A.P. KOHN ET AL.
correlation indicates that the amount of size
or shape change is greater on the right than
on the left when the left side is flattened (or
change on the left is greater on the left than
on the right when the right side is flattened).
There is a significant negative correlation of
direction of modification with size asymmetry a t bregma-pterion (r = -0.35, P = 0.04)
and pterion-asterion (r = -0.51, P = 0.002),
and a significant positive correlation of
direction and asymmetry for asterion
(r = 0.57, P < 0.001) and bregma-asterion
(r = 0.57, P < 0.001).Thus both a size reduction a t asterion and bregma-asterion on the
side of modification, and a size increase a t
bregma-pterion and pterion-asterion on the
side that is modified are implied. There is
no significant asymmetry for size change at
landmarks in the cranial base or face.
DISCUSSION
These results indicate that unintentional
cranial vault modification by cradleboarding
effects cranial vault morphology in a predictable manner. Specifically, localized restriction of cranial vault growth by the cradleboard results in compensatory growth
through much of the cranial vault. The effect
of cradleboarding is generally limited to the
cranial vault, however, and this form of cranial vault modification has little effect on
the morphology of the cranial base and face.
These results support Moss’s (1958) findings that posterior cranial vault flattening
did not significantly affect the morphology
of the cranial base. Cranial vault flattening
in this sample of Hopi appears to have a
more extensive effect on the morphology of
the cranial vault than was observed by
Heathcote (1986) in samples from Kodiak
and Kagamil Islands.
Asymmetric localized size change in the
cranial vault is associated with cradleboarding. Asymmetric flattening of the posterior
cranial vault is associated with decrease a t
asterion and bregma-asterion, and lengthening a t bregma-pterion and pterionasterion on the modified side of the cranial
vault. However, cradleboarding does not produce localized size change asymmetry in the
cranial base or face. There is little significant
asymmetry in localized shape change. These
results contrast with those of Bjork and
Bjork (1964) who analyzed crania from Peruvian coastal and highland samples. They observed that asymmetry of the length of the
cranial base and maxilla showed a significant positive correlation with direction of
modification of the cranial vault. That is, the
lengths of the cranial base and maxilla were
shorter on the modified side of the cranium.
The effects of cradleboarding on cranial
development can be contrasted to those of
intentional cranial vault modification by
headdresses or head wraps. In the case of
the Hopi, cradleboarding results in pressure
being applied to a limited area of the cranial
vault, and the morphological effects of cradleboarding are largely limited to the cranial
vault. In contrast, antero-posterior modification and annular modification both result
from pressure applied to the cranial vault
in multiple directions (Dingwall, 1931).Both
forms of intentional cranial vault modification have significant effects on the growth
and morphology of the cranial base and face
(Cheverud et al., 1992; Kohn et al., 1993).
Antero-posterior modification of the cranial
vault results in a n anterior-posterior decrease and a medial-lateral increase in
growth a t landmarks in the cranial vault,
cranial base, and face (Cheverud e t al.,
1992). Intentional antero-posterior modification (as practiced by prehistoric people
from Ancon) and bilateral modification by
cradleboarding modify the posterior cranial
vault in the same directions. Annular modification of the cranial vault produces a n anterior-posterior increase and medial-lateral
decrease in growth a t landmarks in the cranial vault, cranial base, and face.
The localized effects of cradleboarding on
the growth of the cranial vault, cranial base,
and face are similar to those observed in
scaphocephaly (Kohn et al., 1994). Scaphocephaly, or premature closure of the sagittal
suture, also produces a localized restriction
on growth of the cranial vault. Restriction of
medial-lateral growth at the sagittal suture
significantly affects the shape of the cranial
vault; however, the morphology of the cranial base and face are within the normal
range for the sample.
It appears that there is a n interrelationship between the growth of the cranial vault,
ASYMMETRIC VAULT MODIFICATION
cranial base, and face. However, localized
modification of the craniofacial complex does
not always affect the growth of other regions
of the craniofacial complex. Localized or unidirectional disturbances in direction of cranial vault growth, such as those resulting
from cradleboarding or scaphocephaly, fail
t o produce growth changes in the cranial
base and face. In contrast, general and multidirectional disturbances in direction of cranial vault growth significantly influence the
growth of the cranial base and the face. Similar conclusions arise from the experimental
vault modification (Pucciarelli, 1978) and
premature closure of cranial sutures (Babler
and Persing, 1982; Babler et al., 1987; Babler, 1988, 1989), and from craniosynostoses
(Moss, 1959; Kreiborg, 1981, 1986; Kreiborg
and Pruzansky, 1981; David et al., 1990,
1982; Richtsmeier, 1985, 1987, 1988;Richtsmeier et al., 1991).
These results indicate that anthropological studies of population variability can
readily include samples from populations
that practiced cradleboarding. Since cradleboarding does not effect the morphology
of the cranial base and face, inclusion of dimensions from these regions should not introduce bias in analyses of genetic differences between populations. Thus, biological
distance studies of prehistoric or protohistoric groups should not be distorted by the
inclusion of these dimensions.
ACKNOWLEDGMENTS
We thank Dr. Glenn Cole and the Field
Museum of Natural History for access to the
skeletal collection. We also thank Dr. Joan T.
Richtsmeier for making MGPA and FIESCA
available to us. Dr. Lyle W. Konigsberg was
very helpful in the early stages of this project. Nyuta Yamisita and Dr. Jim Midkiff
were helpful in collecting the dta, and Susan
Jacobs was helpful in the data analysis.
Three anonymous reviewers provided helpful comments on this manuscript. This research was supported by NSF grant BNS8910998.
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