The Taung endocast: A reply to Holloway

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 60479-48X1983)

The Taung Endocast: A Reply to Holloway DEAN FALK Department of Anatomy, and Caribbean Primate Research Center, University of Pllerto Ricq Medical Sciences Campus, San Juan, Puertn Rico 00936

KEY WORDS Lunate sulcus, Stereoplotting, Taung

Australopithecines, Brain, Chimpanzees, Endocasts,

ABSTRACT Indices of rostrality (i,, i,’) are developed to assess the extent to which the medial end of the lunate sulcus (L) is rostrally positioned in photographs and figures of lateral views of primate brains and endocasts, and indices are determined for chimpanzees, SK 1585 and the Taung endocast. I, quantxies the extent of rostrality as it has traditionally been viewed (in A-P projections) while i,‘ takes dorsal curvature into account. The i,. of the feature that I have identified as the lunate sulcus of Taung is within one standard deviation of the mean i, for Pan and its i,’ is within 1.5 standard deviations from the mean i,’ for Pan. Both findings are compatible with my earlier statement that the medial end of the lunate sulcus of the Taung endocast is in a pongid-like position. Use of stereoplotting to transfer the position of L from chimpanzee endocasts and brains to australopithecine endocasts is critically assessed Holloway stereoplotted five chimpanzee brains and then transferred their mean coordinates that describe the lunate sulcus to the Taung endocast. If stereoplotting successfully transfers the extent to which L is rostrally located, one would expect the mean L of Pan and its transferred counterpart in Taung to have identical index values of rostrality. However, the i, of the lunate sulcus that Holloway located on Taung is over two standard deviations lower than the mean i, for the five chimpanzees he stereoplotted to determine its angular coordinates, and Holloway’s i,‘ for Taung is one standard deviation lower than the five chimpanzees’ mean i,’. These discrepancies are shown to be due to shape differences, and it is concluded that stereoplotting should not be used to transfer sulci between differently shaped endocasts without correcting for these differences. I also reply to Holloway’s criticisms of my use of L/H indices, palpation, techniques for sampling endocasts, and illustration of the Taung endocast. It is shown that there is mom on the Taung specimen for the lateral end of L, and the pongid-like sulcal pattern of Taung is reaffirmed. Thus, we do not yet know when human-like sulcal patterns first appeared in the hominid fossil record.

In an earlier report (Falk, 1980a), the sulcal pattern of the Taung endocast was compared lobe-by-lobe and feature-by-feature to sulcal patterns of gorillas, chimpanzees, and humans; it was shown that the sulcal pattern of the Taung specimen was pongid-like rather than human-like as previously stated by Dart (1925), Schepers (Broom and Sche- pers, 19461, and Holloway (1974, 1975). Hol- loway (1981) has recently criticized my analysis of the South African australopithecine natural endocasts. Holloway used a ster-

eoplotting technique to determine the approximate coordinates of the lunate sulcus on five chimpanzee brain casts. He then transferred the average coordinates of the Pan lunate sulcus to the Taung endocast, a procedure that resulted in a lunate sulcus that was more caudally placed than the feature that I identify as the medial end of the lunate sulcus. Thus, Holloway concluded that

Received December 21,1981; accepted October 15.1982.

0 1983 ALAN R. LISS, INC.

480 D. FALK

Fig. 1. The natural endocast from the Taung specimen of Australopithecus afiicanus from Falk (1980a). The coronal and lambdoid sutures, vessels, and all damaged areas are illustrated and crassed hatching indicates adhering bony fragment. Abbreviations of sulci modified

the feature I identify as the lunate sulcus is located too far rostrally to be in a pongid-like position. Holloway also discussed his visual perceptions of sulci on the Taung endocast in conjunction with a highly critical discussion of my interpretation of the endocast (Fig. l), although he declined to provide his own illustration of the Taung endocast. This report replies to Holloway’s contentions regarding the Taung endocast.

MATERIALS AND METHODS

A white plaster copy of the Taung endocast, that was prepared by Mr. Alun Hughes, was reexamined in light of Holloway’s (1981) re- cent comments. In 1978, I had the opportu- nity to compare this copy feature-by-feature with the original specimen and to ascertain that it is an excellent replica of the fossil.

Previous discussions about the position of the lunate sulcus have relied on “eyeballing” lateral views of primate brains and describing how far rostral or caudal the sulcus is positioned. For example, Holloway (1974) used this approach to establish that lunate sulci of apes are more rostrally positioned than lunate sulci of humans: “In all ape brains the lunate sulcus lies relatively far forward ..... In modern man, when the lunate sulcus appears at all ..... it lies much closer to

after Connolly (1950): a2, angularis; as, anterior oeeipi- tal; fm, frontalis medius; fo, fronto-orbital, fs, frontalis superior; h, horizontal ramus pci; L, l u t e ; lc, lateral calcarine; oci, inferior occipital; p i , precentral inferior; r, &us; tm, temporalis medius; ts, temporalis superior.

the far end of the occipital pole.” In the present report, two indices of rostrality (ir, ir’) are developed to quantify comparisons of the position of the lunate sulcus in lateral views of brains (endocasts) of australopithecines and pongids. This analysis is confined to the medial end of the lunate sulcus because that is the portion of this sulcus which I have ten- tatively identified on the Taung endocast. However, the question of whether or not there is room for the lateral portion of the lunate sulcus on the Taung endocast will be addressed below.

Figure 2 illustrates the projection index of rostrality (i,) which can be determined from photographs of lateral views of endocasts or brains. Vertical lines are drawn at the occipital pole (op), medial end of the lunate sulcus (L) and frontal pole (fp). The shortest distance between the lines representing op and L (x in Fig. 2) and op and fp (y in Fig. 2) are measured from the photograph with sliding calipers and the index is determined by com- puting the ratio dy. Thus i, = d y and, since the index is a ratio, indices determined from differently scaled photographs may readily be compared. Larger index values indicate a more rostral (forward) position of the medial end of the lunate sulcus than do smaller values. It should be emphasized that this index

THE TAUNG ENDOCAST 481

Fig. 2. Methods for determining index values of rostrality (i,, i;) for the medial end of the h a t e sulcus from photographs of lateral views of brains or endocasts. For the projection index (iJ, vertical lines are drawn at the occipital pole (op), frontal pole (fp), and medial end of the h a t e sulcus 6). The distances between lines representing op and L (=x) and op and fp (=y) are measured with sliding calipers (mm). The ratio i, = x/y is computed for each photograph and larger ratios indicate a more

quantifies the extent to which the lunate sulcus is rostrally located as it has traditionally been discussed, i.e., in an A-P projection, how far forward is the sulcus located?

The projection index (ir) does not take brain (endocast) curvature into account, however. In order to quantify the extent to which the medial end of the lunate sulcus is rostrally positioned and to incorporate information about the extent of doming (curvature), another profile index &’) was developed. Figure 2 illustrates ir’ which can be determined from photographs of lateral views of endocasts or brains. One piece of flexible wire is used to measure the distance between op and fp along the dorsosagittal curvature and the projection of the medial end of the lunate sulcus is marked directly on the wire. The wire is then straightened and the distances between op and L (x’) and op and fp 0.’) are measured from the wire with sliding calipers. The profile index is determined by com- puting the ratio i,’ = x‘/y’. This method of assessing how far rostral the lunate sulcua is positioned is preferable to stereoplotting the approximate coordinates of the sulcus with

rostral Iforward) position of the medial end of the lunate mlcua than do smaller indices. Thus, i, quantifies the extent to which the medial end of the lunate sulcua is rostrally positioned, as it has traditionally been viewed. Unlike ir, the profile index (ir‘ = x’/y’) takes dorsal curvature (shape differences) into account. Since i, and i,’ are ratioe. corresponding index values from differently scaled photographs are comparable.

two angular coordinates only (i.e., without radial distances, as in Holloway, 19811, because variation in endocast shape will not confound attempts to use the index determined from a photograph of one specimen to position the medial end of the lunate sulcus on another specimen (see below).

Projection and profile index values were determined from five photographs of lateral views of chimpanzee brain casts from Hollo- way (1981, Fig. 2) as well as photographs of one chimpanzee brain in the author’s collection. Op, f p and L are clearly visible in all the photographs and each specimen appears to be properly aligned in lateral view. Index values were also determined h m Hollo- way’s (1981, Fig. 3) photograph of SK 1585 (a presumed robust australopithecine) on which he imposed a l m t e sulcus, Holloway’s (1981, Fig. 5) photograph of the Taung endocast on which he positioned two lunate sulci (one his, one mine), and ir was determined from my diagram of the Taung endocast in which I identified a medial end of the lunate sulcus (Fig. 1). These index values are listed in Ta- ble 1.

TAB

LE 1.

Rel

ativ

e po

sitio

n of

lun

ate

sulc

us in

chi

mpa

nzee

s an

d fo

ssil

horn

inid

s

Proj

ectio

n in

dex

(ir)

Pr

ofile

inde

x (i,

') So

urce

of

I,=

i,'

= ph

oto-

X

Y

dY

n

mea

ni,

s x'

y'

x'

ly'

n m

eani

,' S

gr

aphs

Pan

10.0

60.5

8.4

57.0

10.5

63.8

7.0

59.8

10.8

66.5

12.8

69.6

SK 1585

11.4

105.3

Tau

ng

14.6

136.2

Tau

ng

11.8

66.8

Taune

24.6

136.2

0.165

1 19.2 82.4

0.233

1 0.147

2 20.1 84.4

0.238

2 0.165

3 18.4 84.6

0.217

3 0.117

4 14.0 79.7

0.176

4 0.162

5 0.151

0.021

21.2 90.6

0.234

5 0.220

0.026

0.184

6 0.157

0.023

25.9 101.2

0.256

6 0.226

0.027

Hol

low

ay's

plac

emen

t of P

an lu

nate

sul

cus o

n au

stra

lopi

thec

ine e

ndoc

asts

: 0.108

1 30.9 151.1

0.205

0.107

2 0.108

37.2 192.0

0.194

2 0.200

Falk

's id

entif

icat

ion

of m

edia

l lun

ate

sulc

us on

Tau

ng e

ndoc

ast

--

-

0.177

1 0.181

2 0.179

49.8 192.0

0.259

1 0.259

Hol

low

ay, 1981, Fi

g. 2

Hol

low

ay, 1981, Fi

g. 2

Hol

low

ay, 1981, Fi

g. 2

Hol

low

ay, 1981, Fi

g. 2

Hol

low

ay, 1981, Fi

g. 2

Thi

s stu

dy'

p F H

ollo

way

, 1981, Fi

g. 3

Hol

low

ay, 1981, Fi

g. 5

f:

Falk

, 1980, Fi

g. 1B.

Hol

low

av. 1981. F

ig. 5.

'This

entr

y re

pres

ents

ave

rage

s of

mea

sure

men

ts fr

om p

hoto

grap

hs of

righ

t and

left

hem

isph

eres

of o

ne c

him

panz

ee br

ain.

In

dex

valu

es o

f roa

tral

ity (i

. =

x/y

for p

roje

ctio

n distances, i.'

= x

'/y'

for c

urve

d di

stan

ces)

for

the

med

ial e

nd o

f the

ha

te su

lcus

of c

him

panz

ees,

the

SK 1

585

endo

east

, and

the

Taun

g en

doea

st d

eter

min

ed as

disc

usse

d in

the

text

and

illu

stra

ted

in Figure

2. E

ntri

es m

easu

red

from

pho

togr

aphs

(figures) in

mill

imet

ers.

Not

ice

that

Hol

low

ay's

i, =

0.1

08 fo

r au

stra

lopi

thec

ine

endo

cast

s fal

ls o

ver t

wo

stan

dard

dev

iatio

ns short

of th

e m

ean

i, o

f 0.1

51 fo

r the

five

chi

mpa

nzee

s he

ster

eopl

otte

d as th

e ba

sis f

or p

ositi

onin

g th

e lunate s

ulci

on

the

aust

ralo

pith

ecin

e en

doca

ats.

Sim

ilarl

y, H

ollo

way

's i,'

= 0

.194

for t

he Taung en

doca

st fa

lls o

ne s

tand

ardd

evia

tion

shor

t of t

he m

ean

i,' o

fO.2

20 fo

r Pan

(n =

5). If

ster

eopl

ottin

g w

ere

a re

liabl

e m

etho

d fo

r de

term

inin

g th

e ex

tent

to w

hich

a s

uleu

s is

ros

tral

ly p

ositi

oned

, Hol

low

ay's

mea

n in

diee

s fo

r Pan

and

the

corr

espo

ndin

g in

dice

s for

aus

tral

opith

ecin

es

wou

ld b

e id

entic

al. S

hape

diff

eren

ces

acco

unt f

or th

e di

scre

panc

ies.

An

inde

x of 0

.179

for

Falk

's id

entif

icat

ion of the

med

ial e

nd o

f the

luna

te sulcus on

the

Tau

ng e

ndoc

ast i

s w

ithin

on

e st

anda

rd d

evia

tion of th

e chimpanzee m

ean

i, (i.

e., 0

.157

f 0

.023

) and

Fal

k's

prof

ile in

dex

of 0

.259

for

Tau

ng is

with

in 1

.6 s

tand

ard

devi

atio

ns &

om th

e ch

impa

nzee

mea

n i.'

(0.2

26 f 0

.041

). B

oth

thes

e fi

ndin

gs ar

e co

mpa

tible

with

the

stat

emen

t tha

t the

luna

te s

ulcu

s of t

he T

aung

epec

imen

is in

a p

ongi

d-lik

e po

sitio

n. S

ee te

xt fo

r dis

cmio

n.


The two profile ir”s calculated from Hollo- way’s Figure 5 required an estimation of where fp would project to in the midsagittal plane since the frontal pole is obscured in the Taung endocast. In order to conservatively compensate for the missing pole, I drew a horizontal line through the occipital pole and parallel to the inferior edge of Holloway’s Figure 5 (since the endocast appears to be properly aligned in lateral view). The dorsosagittal curvature was extended from its most rostral point vertically down to the horizontal line. This added only 9 mm to the op- fp profile of Taung (Fig. 5 is an enlarged view of the Taung endocast), but is an improve- ment over no frontal pole at all. This correc- tion is conservative, and I think the ir”s determined from Holloway’s Figure 5 are still slightly enlarged because of the obscured frontal pole. It should be noted, however, that the estimated 192 mm curvature distance between op and fp of Taung was used as the basis for determjning i,‘ for both Holloway’s placement and my identification of the medial end of L on this specimen (Table 1). The two projection i,‘s calculated from Hollo- way’s photograph of the Taung endocast, on the other hand, utilized the most rostral extension of what is preserved of the frontal lobe as an estimate of fp. Thus, ir)s determined from the Taung specimen are defi- nitely enlarged slightly because the frontal pole is obscured.

Measurement error

In order to test for possible error inherent in measuring photographs, projection and profile index values were determined with calipers, rulers, and twine directly on both hemispheres of a chimpanzee brain in the author’s collection; and on a brain cast of the chimpanzee brain shown in the lower part of Holloway’s Figure 2 (1981), from which I had already determined index values (Table 1). When measuring the position of the lunate sulcus on the brain, care was taken to measure the position of this feature slightly lateral to the midline, i.e., in a position comparable to that of the most medial portion of L that is visible in photographs. (The feature that I have identified as L on the Taung endocast is also located lateral to the midline). The projection index was also measured directly from a copy of the Taung endocast. Lateral views of both hemispheres of the chimpanzee brain were then photographed (Fig. 3) with the hemispheres ori-

ented similar to the chimpanzee brains pictured in Holloway (1981). Projection and profile index values were measured from small prints of the photographs. All measurements on actual brains, endocasts and photographs were repeated at a later date and mean index values were determined by averaging the pairs of measurements.

The projection index of 0.181 determined from Holloway’s photograph of Taung (Table 1) was 3% larger than the mean index of 0.175 determined directly from the specimen. The projection index determined from the photograph of the right chimpanzee hemisphere was 2% less than the measurement on the brain itself, while the projection index determined from the.photograph of the left hemisphere was 3% greater than the comparable measurement from the brain. The dif- ference in profile index values determined from photographs of chimpanzee hemispheres and those taken from the brain itself averaged 4%. Finally, the mean i, determined directly from the brain cast of a chimpanzee hemisphere was 3% larger than that determined from its photograph (0.167 vs 0.1621, while i,’ determined from the cast was 2% larger than its photographic counterpart (0.238 vs 0.234). Thus, measurement error due to all factors, including human and mechanical (e.g., photographic distortion of peripheral images, etc.) is less than or equal to 4%.

RESULTS Index values from brains

A projection index value of 0.201 was determined directly from the right hemisphere of a chimpanzee brain (Fig. 3); whereas the i, measured directly on the author’s copy of the Taung right hemisphere was 0.175. If the frontal lobe of the Taung endocast were not obscured, its i, would be even smaller. Thus, direct measurements on a chimpanzee brain and the Taung endocast reveal that the lunate sulcus of the chimpanzee brain is located more rostrally than the feature that I identify as the medial end of L on the Taung endocast The profile index could not reasonably be estimated directly from the Taung specimen since its frontal pole is obscured (see below, however).

Index values from photographs Table 1 lists index values for the medial

end of the lunate sulcus for chimpanzees, SK 1585 and the Taung endocast. The mean pro-

484 D. FALK

Fig. 3. Right hemisphere of chimpanzee brain that was measured directly and in photographs to determine projection (i,) and profile (i,‘) values for the position of the lunate sulcus. Index values determined from photographs differ less than or equal to 4% from those determined directly from the brain. A comparison of the

jection index for Pan is i, = 0.157 (F = 0.023). The i, for the feature that I have identified as the medial end of the lunate sulcus on the Taung endocast was calculated from both my Figure 1B (1980a) and Holloway’s Figure 5 (1981). The mean of the two calculations is 0.179. Although this index is slightly too large because the frontal pole is obscured in the Taung endocast, the index still falls within one standard deviation of the mean index for Pan (i.e., 0.157 f 0.023). The mean profile index for Pan is i,’ = 0.226 (F = 0.027). The i,’ for my identification of the medial end of L on Taung is 0.259, which falls within 1.5 standard deviations from the mean i,’ index for Pan (i.e., 0.226 f 0.041). Both of these findings are compatible with my earlier statement that the lunate sulcus is in a pon- gidlike position in the Taung endocast (Falk, 198Oa).

projection index value determined directly from the chimpanzee brain with that determined directly from the Taung endocast reveals that the lunate sulcus is positioned more rostrally in this chimpanzee brain than in the Taung endocast. Compare this figure to Fig. 1 and see text for discussion.

Whereas I identified a feature that is visible on the Taung endocast as the medial end of the lunate sulcus, Holloway estimated where the average Pan lunate sulcus would fall on both SK 1585 and the Taung endocast. The mean i, of both placements is 0.108; the mean i,‘ for Holloway’s placement of L on australopithecine endocasts is 0.200 (Table 1). Since the sulci placed on SK 1585 and the Taung cast represent the average chimpanzee sulcus determined from the first five specimens listed in Table 1, one would expect the australopithecine and chimpanzee values to be identical if the method used to “transfer” the lunate sulcus is indeed an accurate meamre of how far rostra1 that sulcus is positioned. However, the 0.108 ir for Taung and SK 1585 is over two standard deviations lower than the 0.151 average i, for Pan, and the 0.194 i,’ for Taung is one standard devia-


tion lower than the 0.220 mean i,’ for Pan. Thus, Table 1 shows clearly that the lunate sulcus Holloway has drawn on the Taung specimen is located further caudally than is the case for the five chimpanzees stereoplotted to determine its coordinates.

DISCUSSION

The failure of Holloway’s stereoplotting method to transfer the average lunate sulcus from five chimpanzee brain casts to its corresponding rostra1 position (as measured by i, and i,’) in australopithecine endocasts is due to endocast (brain) shape differences, rather than to differences in the relative po- sitions of sulci. Holloway described the average chimpanzee lunate sulcus with five points, each one of which was described by two angular coordinates-one for a horizontal angle, the other for a vertical angle. Since “radial distances were not taken as they are irrelevant” (Holloway 1981), no considera- tion (quantification) of endocast shape en- tered into the transferring of one set of average points for Pan to an australopithecine endocast. That is, for each average point determined for Pan, the two angular coordinates were reproduced on the stereoplotter and used to transfer the point to the Taung endocast. As Figure 4 shows, endocast shape influences where points fall on the “trans- feree” endocast and transfer of the lunate sulcus between differently shaped endocasts will alter its index values of rostrality. In short, index values of rostrality yield information about the extent to which a lunate (or other) sulcus is rostrally positioned (in the traditional projection sense or taking curvature into account, see above); stereoplotting does not yield equivalent results because it is influenced by differences in endocast Shapes.

Earlier (Falk, 1980b), I stated that “the possibility of a rubicon based on endocast shape seems more hopeful, but this area needs further research that perhaps utilizes the polar-coordinated steroplotting method- ology of Holloway.” Indeed, an occipital view of the Taung endocast compared to occipital views of brains of other hominoids (Falk, 1980a, Fig. 3) shows that the Taung endocast is shaped differently from the brains of chimpanzees. These shape differences could be in- vestigated through stereoplotting angular coordinates and quantified by the gathering and analyzing of data on the radial distances from surface points to the center points of

endocasts. Thus, contrary to Holloway (1981), I think that radial distances are relevant and necessary to fully explain his results. As stated earlier (Falk, 1980a) “I want to make it quite clear that I am not saying that australopithecine brains were identical to those of pongids ..... these differences are not mani- fest at the level of cortical sulcal patterns, however ....” Quantifying and interpreting endocast (brain) shape differences between australopithecines and pongids with stereoplotting techniques could provide useful information for paleoneurologists. It should be noted, however, that meaningful analyses of endocast shape in australopithecines would require a data base describing brain shapes in pongids (including orangutans, see below) and fossil and extant hominids, since brain shapes run the gamut from brachyencephalic to dolichoencephalic, and from hypsience- phalic to platyencephalic in hominids, if not in pongids.

O W R COMMENTS

Holloway makes several statements about my methods and findings that I would like to respond to:

1) Holloway (1981): “I think Falk places undue stress on palpation as a technique which is somehow more valuable in her study than those of others who have not mentioned it.”

Response: The features 1 have identified on the Taung and other australopithecine endocasts are visible as well as palpable as can be verified by the reader by comparing Figure 1 with a copy of the Taung endocast.

2) Holloway (1981): “Falk notes that only ‘carefully selected’ endocasts were used. My endocast collection is not ‘carefully selected’ except that they are all adult, unbroken specimens. I too have examined the primate brains at the Smithsonian Institute, as well as other institutions, but I found many of them to be distorted given the number of years they have been lying around in fixa- tive solution and jars.”

Response: I used all of the available South African australopithecine natural endocasts. The Smithsonian brains are very well fixed and appeared to me to be just as John Con- nolly illustrated them in 1950. I do carefully select monkey skulls for endocasting (which is beside the point in an australopithecine paper) for the following reasons (Falk, 1978): monkeys are born with the sulci that I study, skulls from juveniles produce better endo-

486 D. FALK

Fig. 4. How transfer of a sulcus from one cast to another by stereoplotting is influenced by differences in cast shape. Coordinates are first determined for the medial end of the lunate sulcus (L) for cast A. For the sake of illustration, the medial end of L is located in the midsaggital plane. The lateral portion of L is not visible in this plane and is therefore indicated by dashes. The two angular coordinates of the medial end of L are h + 30” in the vertical plane and 0“ in the horizontal plane.

casts than do skulls from newborns or adults, and comparison of endocasts from carefully selected skulls with actual monkey brains shows that cortical sulcal patterns are accu- rately reproduced on such endocasts.

3) Holloway (1981): ““he lateral calcarine is deep in Pan, and goes as far caudal as the occipital pole. Note how the lateral calcarine as defined by Falk on the Taung endocast is truncated anterior to the lambdoid suture.”

Response: I neither implied nor stated that lack of the lateral calcarine sulcus caudal to the lambdoid suture on the Taung endocast indicates that the sulcus did not exist in the occipital lobe of Taung’s brain. On the contrary, I stated (Falk, 1980a) that “the occipital lobe of the Taung endocast appears to be smooth caudal to the lambdoid suture. It seems likely that sulci were present, but sim- ply were not reproduced in this region of the endocast, since comparable areas in hominoid endocasts do not reproduce sulci although sulci do exist in the corresponding parts of hominoid brains. Since the occipital regions of the other australopithecine natural endocasts also are blank, we do not yet

Removing cast A from the stereoplotter and replacing it with a correctly positioned but differently shaped (higher domed) cast B results in the medial end of L being transferred caudally in B, relative to its position in A, because the stereoplotter pointer contacts B at a relatively different position Shape differences between casts could be quantified by analyzing radial distances (r) from the center to plotted surface points.

have a good description of the sulcal pattern in the occipital lobe of australopithecines.”

4) Holloway (1981): “Falk has indicated that LeGros Clark’s opinions were based on diagrams of the Taung cast rather than on the originals ..... Falk is incorrect on this mat- ter, and it is reasonable to remind readers of this paper of two important historical facts: (1) by any standards, W.E. LeGros Clark was a superb, widely-reknowned neuroanatomist with a strong comparative interest and train- ing; (2) Raymond Dart was a protege of G.E. Smith, who devoted a very considerable portion of his professional career to the study of the lunate sulcus. Dart’s early publications were in comparative neuroanatomy. These points are only mentioned to indicate that those who did study the original specimens were well-versed regarding comparative neuroanatomy, and the lunate sulcus in particu- lar.”

Response: I was wrong about Clark (1947) not seeing the original specimens. However, the fact that Clark, Dart, and Smith were renowned scientists has nothing to do with where the lunate sulcus is actually located


on the Taun specimen. The line of reasoning used by Hofioway is known to logicians as the urgumentum ad verecundiam and “ap- peals to the prestige of some authority or other must always be treated with suspicion, because to accept opinions out of respect for great men, ancient customs, or recognized institutions is to dispense with evidence and proof. Anyway, intellectual progress de- mands skepticism not submission” (Aubyn, 1976). This, of course, in no way excuses my mistaken statement that Clark did not view the original specimens.

5) Holloway (1981): “.....some of that dam- age is located precisely where Falk has de- cided to locate the lunate sulcus.” Response: I did not decide to locate any

sulci on the Taung endocast. All of the features I describe are visible and palpable on the original specimen and my copy of it. I merely illustrated all features that I per- ceived and identified those that I could. The feature which I have identified as the medial end of the h a t e sulcus (L) is indeed small. I have considered the possibility that this feature might represent the parietooccipital sulcus (PO), but instead identified it as L (the only likely alternative) because po is rarely reproduced on human, ape, or monkey endocasts (Falk, 1980a). Thus, although there is no way to be positive of my identifkation, it is the best one I am able to provide in light of the limited available fossil evidence and comparative primate neuroanatomy.

6) Holloway (1981): “.....the Taung is that of a young child. All of her drawings for pongids and Homo are from adult specimens.”

Response: Figure 7B (Falk, 1980a) reproduced brains of a 5 year old male Homo sap& ens and a young chimpanzee, after Connolly (1950). In the text, I stated (p. 534): “A comparison of the sulcal pattern of the approxi- mately 5- to 6-year-old Taung ‘baby’ (Fig. 1B) with the sulcal patterns of a young chimpanzee (Fig. 7A) and a 5-year-old Homo sapiens (Fig. 7B) will serve to illustrate the pongid- like affinities of the external morphology of the australopithecine brain.”

7) Holloway (1981): “In all of the cases of Pan casts I have examined ..... the lunate sulcus is always anterior to the most rostral extension ofthe lateral cdcurine. It is impossible to place a lunate sulcus anterior to Falk‘s representation of the lateral calcarine without violating the basic morphology of the Taung endocast, that is, the gyral convexi- ties.”

Response: As I discussed earlier (Falk, 1980a1, one cannot determine the exact rostral end of the lateral calcarine sulcus on the Taung specimen because of its close proxim- ity to a nearby damaged area. My best guess from examining the cast, is that lc extends slightly rostral to the middle of the medial border of the nearby damaged area, which is how it is illustrated in Figure 1. Measuring directly on my copy of the Taung specimen, there are a full 10 mm between this point and the nearest sulcus rostral to it (a2). Thus, if my estimation is even roughly accurate, there is ample room for a lunate sulcus anterior to lc and codigurations of lunate sulci similar to those photographed in chimpanzees by Holloway (1981, Fig. 2) could fit in this area without violating the chimpanzee- like relationships with any of the nearby sulci (see also lateral views of chimpanzee brains of Connolly, 1950). It is entirely possible that a portion of the vessel shown medial to the damaged area and directly caudal to a’ in Figure 1 traveled external to the dura mater directly over the lunate sulcus. Thus, as noted earlier (Fa&) 1980a), the meningeal vessel and damaged areas on the Taung endocast may be responsible for the lack of reproduction of the lateral end of the h a t e sulcus.

8) Holloway (1981): “Falk’s use of LM indices is unusual.....Twisting the arguments by injudicious use of indices unfortunately camouflages the very important fact that the height of australopithecine cerebral cortex above the cerebellum was relatively greater than in pongids.”

Response: Holloway (1975) computed a lengthheight 0 index of 1.41 for Taung and used it to argue that australopithecines had higher cerebral cortices than pongids. Using L/H indices, I showed that orangutans have higher cerebral cortices than Taung while some Homo erectus and Neanderthal specimens had lower cerebral cortices and concluded that L/H indices do not separate pongids from hominids (Falk, 1980a). Rather than being “unusual,” “injudicious,” or “twisted,” my use of L/H indices is identical to Holloway’s. We just examined different taxa and arrived at different conclusions.

CONCLUSIONS

One should not use steroplotting to analyze the extent to which a feature is rostrally located without taking shape into account; nor should one use steroplotting to transfer a feature from one endocast to another differ-

488 D. FALK

ently shaped endocast without correcting for shape differences. Stereoplotting may provide a useful technique for quantifying brain (endocast) shape differences, but a large data base must be established for pongids (including orangutans) and extant and fossil hominids before australopithecine brain shape can be analyzed in proper perspective.

The reader may wonder why so much at- tention has been focused on one feature, the lunate sulcus. For years, Holloway has ar- gued that the supposed caudal position of the lunate sulcus in the Taung endocast shows that australopithecines were neurologically “reorganized” like extant humans. For example, (Holloway, 1972): “..... the minimal interpretation is that by the time of the Taung child, the hominid brain was already reorganized in a human direction, regardless of the chimpanzee-like size ....”

The “reorganization” implied by the supposed caudal position of the lunate sulcus in Taung means, according to Holloway (1975): “.....there was a reorganization of the brain involving, minimally, a decrease in primary visual cortex on the convex cerebral surface and an increase in parietal and temporal as- sociation cortex, allowing for greater dis- crimination among complex cues of the environment and for extension of foresight and memo ry....”

Holloway (1975) brought rigor into the field of hominid paleoneurology by providing new and improved estimates of brain size from fossil endocasts. One must be cautious, however, about inferring abilities such as “dis- crimination,” “foresight,” and “memory” from the position of the lunate sulcus. The term “neural reorganization,” as defined in Holloway’s early papers (1966), encompasses profound neurological changes at neocorti- cal, subcortical, and limbic levels. It entails reorganization of cortical tissue (including such parameters as neural density, neurog- lial cells, and dendritic branching) and in- volves levels spanning from sensorimotor systems to neuroendocrine balances (Hollo- way, 1966). Can one state that profound %eura1 reorganization” (i.e., in a human direction) has occurred, based on the placement of the lunate sulcus in a fossil hominid endocast? I, like Radinsky (1979), think not. One should be especially cautious since allome- tric considerations and shape differences, i.e., the “packaging phenomena” referred to by Radinsky (1979) have yet to be elucidated for hominoids. On a more optimistic note, ster-

eoplotting might provide a useful first step in unraveling “packaging phenomena,” since it could be used to quantify brain shapes in different hominoids.

According to Holloway (19811, “there is no dispute regarding Schepers’ figure of Taung. It is incorrect. But neither is Falk‘s drawing accurate.” Holloway devotes much print to discussion of individual sulci on my figure of the Taung endocast and describes in detail the ways in which his visual perceptions and interpretations differ from my own. Never- theless, he refuses to illustrate his perceptions, claiming that the endocast is too damaged to permit accurate sulcal identifi- cations. If both Schepers’ and my illustra- tions are inaccurate, then an accurate illustration of the Taung endocast has yet to be published, and Holloway should provide readers with a figure of the Taung endocast in which he illustrates and identifies (where possible) damaged areas, pits, sulci, and vessels. Meanwhile, I have reexamined my copy of the Taung endocast in light of Holloway’s comments and it continues to appear to me as illustrated in Figure 1. For reasons delin- eated in Falk (1980a), the entire sulcal pattern of the Taung endocast appears pongid- like. Thus, we do not yet know when human- like sulcal patterns first appeared in the horn inid fossil record

ACKNOWLEDGMENTS

The author thanks Mr. Ernie Davis for helpful discussions about stereoplotting and for suggesting Figure 4, Drs. Leonard Radin- sky and Walter Inge for criticisms of the manuscript, Mrs. Lydia Warlop for typing the manuscript, and Dr. Robert Waide for holding down the other end of the wire. I am grateful to Professor Phillip Tobias of the Department of Anatomy, University of Wit- watersrand, for permitting me to examine the Taung endocast, Mr. Alun Hughes for kindly providing me with a plaster copy of the specimen, and to Dr. Wally Welker for providing a brain cast of a left hemisphere of a chimpanzee brain. The fieldwork upon which this research is based, was supported by National Science Foundation grant BNS 78-05514.

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Aubyn, St G (1976) The Art of Argument. New York

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Clark, WE Le Gros (1947) Observations on the anatomy of the fossil Australopithecinae. J. Anat. 81:300-333.

Connolly, C J (1950) External Morphology of the Primate Brain. Springfield, Illinois: C.C. Thomas.

Dart, RA (1925) dustralopithecus afiicanua- The man- ape of South Africa. Nature (Lond). 115:195-199.

Falk, D (1978) External Neuroanatomy of Old World Monkeys (Cercopithecoidea). Contrib. Primat. 151-95.

Falk, D (1980a) A reanalysis of the South African australopithecine natural endocasts. Am. J. Phys. Anthro- pol. 53:525-539.

Falk, D (1980b) Hominid brain evolution: The approach from paleoneurology. Yearbook of Phys. Anthropol.

Holloway, RL (1966) Cranial capacity and the evolution of the human brain. Am. Anthropol. 68:103-121.

Holloway, RL (1972) Australopithecine endocasts, brain evolution in the Hominoidea, and a model of human

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evolution. In R Tuttle (ed): The Functional and Evolu- tionary Biology of Primates. Chicago: Aldine, pp. 185- 204.

Holloway, RL (1974) The casts of fossil hominid brains. Sci. Am. 231:106-115.

Holloway, RL (1975) The Role of Human Social Behavior in the Evolution of the Brain. Forty-third James Ar- thur Lecture on the Evolution of the Human Brain. New York The American Museum of Natural History.

Holloway, RL (1981) Revisiting the South African Taung australopithecine endocask The position of the lunate sulcus as determined by the stereoplotting technique. Am. J. Phys. Anthropol. 561.43-58.

Radinsky, LB (1979) The Fossil Record of Primate Brain Evolution. Forty-ninth Janes Arthur Lecture on the Evolution of the Human Brain. New York The Amer- ican Museum of Natural History.

The Taung endocast: A reply to Holloway

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