MORPHOLOGICAL DISTANCE BETWEEN AUSTRALOPITHECINE, HUMAN AND APE SKULLS
Human Evolution 11: 35-41, 1996
This paper attempts to quantify the morphological difference between fossil and living species
of hominoids. The comparison is based upon a balanced list of craniodental characters
corrected for size (Wood & Chamberlain, 1986). The conclusions are: craniodentally the
australopithecine species are a unique and rather uniform group, much nearer to the great apes
than to humans; overall, their skull and dentition do not resemble the human more than the
chimpanzee’s do.
Key words: human evolution, hominids, apes, skull, Australopithecus, Homo erectus,
chimpanzee, gorilla
Introduction
The australopithecine species are commonly considered to be “hominids” beeause they
lack some of the features that characterize the living apes, and display certain humanlike
characters. Yet it has often been argued that their humanlike characters might be primitive and indeed many of these characters are found in premature African apes - and that the
australopiths should not be included in the evolutionary branch towards humans, but instead
are a unique group of apes or might even be closer phylogenetically to the African apes than
to humans (e.g., Kleindienst, 1975; Goodman, 1982; Gribbin & Cherfas, 1983; Oxnard, 1984;
Hasegawa et al., 1985; Edelstein, 1987; Verhaegen, 1990; 1994).
The aim of this paper is to objectivate morphological resemblances of
australopithecine species with living hominoid species. (To establish phylogenetic
relationships, biomolecular comparisons of nucleic acids or proteins are preferable to
morphological comparisons, but it does not seem very probable that extraction of enough
DNA or protein from fossil bone will ever become possible.)
Methods
I have used the comparative data of Wood and Chamberlain (1986) because:
 Their data are likely to be comparable since they stem from the same source.
 They use a balanced list of 39 characters, i.e., "selected to provide a relatively
comprehensive coverage of the head" without much functional or morphological
overlapping. The 39 characters stem from: cranial vault and endocranium (11 V), face (7
F), palate and maxilla plus dentition (7 P), cranial base (5 B), and mandible plus dentition
(9 M).
 Wood and Chamberlain do not use the "raw" metrical data, but ratios, which "help to
reduce, if not actually eliminate, differences due to absolute size".
Postcranial data (more scarce and difficult to attribute to a certain species) are not
included in their list.
Since the data for the 39 characters were not available for all species, I selected two
(overlapping) Character Groups (only characters V9 and B5 were not used at all):
I. one of 32 characters (82 %) that were available for 8 species: Hylobates, Pongo, Pan
troglodytes, Gorilla, A. africanus, A. boisei, H. erectus and H. sapiens (characters V1-8,1011, F1-7, P1-3,5-6, B1,4, M-6,8-9);
II. one of 27 characters (69 %) that were available for 7 species: Pongo, Gorilla, Pan
troglodytes, Homo sapiens, Australopithecus africanus, A. robustus and A. boisei (characters
V1,7-8, F1-7, P1-7, B1-3, M1,4-9). This second Group was added since it included data from
a third australopithecine species, A. robustus.
The data for Pan paniscus, A. afarensis and H. neanderthalensis could not be used,
since they were available for too few characters. The data for “H. habilis” (which included
ER-1470, ER-1813, and OH material) were not used since they might belong to more than
one species.
A simple method measured the relative overall craniodental distance between the
different (fossil as well as living) hominoid species without considering any of these species
as an outgroup a priori:
Each character had to have equal weight. For each species and each character, the sum
of the differences with the same character in the other species was given an arbitrary weight
of 1000, i.e., each of the differences with the other species was divided by the sum of these
differences and multiplied by 1000. Tables Ia and IIa show the mean results of all (32 or 27)
characters for all (8 or 7) species. These results, of course, are not directly proportional to the
morphological distance, but indicate that the difference between species A and B is larger or
smaller than that between A and C. As an example, Figure 1 shows the calculation of the
results for Character Group II (and more in particular for A. boisei).
These results in Tables Ia and IIa for each species were made more comparable with
those for the other species in the same Character Group (e.g., for interpreting the diagrams,
see below) by multiplying them by a correction factor consisting of the sum (/1000) of the
differences of the other species with that species (see Figure l). This yielded Tables Ib and IIb.
(This correction exaggerates the results of the most aberrant species (e.g., H. sapiens in Table
II), but does not change the order of differences.)
For illustrating which one of the living species resembled a fossil species most, the
diagrams of Figure 2 were constructed. Since all results are relative, the diagrams could be
made clearer by equalling one of the species to zero. In this case, Pongo, which was nearest to
the mean species, was taken as the reference (this choice, of course, does not influence the
conclusions): in Tables Ib and IIb, the results comparing Hylobates, Gorilla, P. troglodytes
and H. sapiens with the fossils were subtracted from the results of Pongo, so that a positive
result (above the x-axis) means that the fossil resembles the living species more than it
resembles Pongo craniodentally; a negative (below the x-axis), less.
(For comparing the diagrams between both Character Groups, the results for Group I
could have been multiplied by 5198/3954, which is the quotient of the sums of the differences
within Group II and I using only the species common to both Groups (i.e., omitting the results
for H. erectus, A. robustus and Hylobates). This second correction factor (even less than the
first) would not have influenced the conclusions.)
Discussion
The tables show that morphologically the great hominoids form three clusters: Homo,
the australopithecines, and the great apes.
1) The human skull is unique and differs from that of the great apes even more than the
gibbon does. Homo is about equidistant from australopithecines and chimpanzees (though
evolutionarily he is probably closer to A. africanus than to Pan, only because A. africanus
lived almost three million years nearer to the common ancestor). H. erectus in Group I seems
to be on the way to H. sapiens. He is about equidistant from H. sapiens, P. troglodytes and A.
africanus, but differs from the australopithecines even slightly more than Pongo does.
2) The australopithecine skulls resemble each other more than they resemble the apes (even
the African apes) and certainly humans; A. robustus stands somewhere between A. africanus
and A. boisei, but nearer to A. boisei. In comparison with the living species (Figure 2):
 A. africanus in both Character Groups is closest to the chimp, and closer to chimpanzees,
gorillas and orangutans than to humans (and to gibbons in Group I);
 A. robustus in Group II also is morphologically closest to the chimpanzee, and much
closer to chimp, gorilla and orang than to humans (gibbons were not included in this
comparison);
 A. boisei in both Groups is closer to G. gorilla than to Pan troglodytes (in contrast with
the South African fossils), and very different from Homo, somewhat more different than
A. africanus is from Homo.
A. boisei (who lived later) more than A. africanus (who lived earlier) resembles the living
African apes compared with humans or orangs or gibbons (Figure 2). In Diagram II of Figure
2, A. robustus also resembles the African apes more than A. africanus does in comparison
with humans. This indicates that the australopithecines (from graciles to robusts) were
evolving in the African ape direction - whether in parallel with the apes (see Ferguson, 1989)
or not (Verhaegen, 1994).
3) The great apes (even including Pongo) resemble each other even more than H. erectus and
H. sapiens in Group I resemble each other, in spite of the evolutionary distance between the
apes (cf. the African apes and Pongo split perhaps ten times earlier than H. erectus and H.
sapiens). They resemble each other more than A. boisei resembles A. africanus. This points to
a remarkable degree of conservatism and/or of parallelism in cranial evolution of these three
great ape species (and to a remarkably fast evolution of Pleistocene Homo). Yet, chimps,
somewhat more than gorillas, resemble Homo more than orangs and certainly gibbons do (in
accordance with the biochemical resemblances).
All this implies that the craniodental evidence provides no ground for the anthropological
custom of using the living African hominoids as an outgroup when comparing
australopithecines with humans or when reconstructing hominoid phylogenetic trees: if the
australopithecine species are considered to be hominid, the great apes and certainly the
African apes should also be called hominid, since they resemble the australopiths more than
humans do, and they do not differ from humans more than the australopiths do (Figure 3).
The australopithecines are often assumed to be hominids on the basis of their
postcranial features (not included in Wood and Chamberlain’s list), but many authors argue
that locomotorically australopithecines differed more from humans than from the African
apes (for discussion and references, see especially Oxnard, 1984; and Verhaegen, 1990, 1993,
1994). In this respect too, the australopithecines could have had unique adaptations (Oxnard,
1984) for an environment or lifestyle that no longer exist. (For instance, there is dental as well
as paleo-environmental evidence that the later australopiths fed partly on bamboo or reed or
papyrus (Du Brul, 1977; F. E. Grine, pers. comm.; Puech, 1992, and pers. comm.; Verhaegen,
1992), possibly wading bipedally in the shallow waters where most fossils are discovered
(discussion in Verhaegen, 1993).)
Although Gorilla and Pan skulls resemble each other morphologically (Tables Ib and
IIb), both species differ biochemically (in DNA and proteins) even more than Homo and Pan
(e.g., Horai et al., 1995). Since synchronous parallel evolution in related species in response
to a climatic change appears to be the rule (e.g., White and Harris, 1977; Seger, 1987, Gibbs
and Grant, 1987; Bown et al., 1994; theoretical considerations in Silson, 1988), some African
ape features that are usually assumed to be primitive might instead have developed in parallel
in gorillas and in chimpanzees. The possibility should even be considered that, if australopiths
are more closely related to the African apes than to humans (be it, of course, on
morphological grounds, see Figure 3), some australopithecines might evolutionarily be closer
to chimpanzees and others to gorillas (discussion in Verhaegen, 1994).
Conclusions
This comparison of 37 craniodental characters of fossil and living apes and humans
yields no indication that any of the australopithecine species has evolved in the human
direction. South African australopithecine skulls are morphologically closest to the
chimpanzee among the living hominoids, and A. boisei is closest to the gorilla among the
living hominoids. Human craniodental evolution appears to have been very fast the last one or
two million years.
These conclusions could be verified and extended when more (including postcranial)
data on living (e.g., P. paniscus) and fossil hominoids (adult and premature) will become
available.
Tables
Craniodental differences between hominoid species.
Tables Ia and Ib based on 32 characters (8 species).
Tables IIa and IIb based on 27 characters (7 species).
Tables Ib and IIb corrected (see text and Figure 1).
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Ferguson W.W., 1989. A new species of the genus Australopithecus Primates-Hominidae
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Seger J., 1987. El Nino and Darwin's finches. Nature, 327: 461.
Silson R.G., 1988. Additive Genes in Evolution and Selection. Tring: Greenfield Publications.
Verhaegen M., 1990. African ape ancestry. Human Evolution, 5: 295-297.
Verhaegen M., 1992. Did robust australopithecines partly feed on hard parts of Gramineae?
Human Evolution, 7: 63-64.
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220-248, Cambridge University Press, Cambridge.
AUSTRALOPITHECINES: ANCESTORS OF THE AFRICAN APES?
Human Evolution 9: 121-139, 1994
Since australopithecines display humanlike traits such as short ilia, relatively small front teeth
and thick molar enamel, they are usually assumed to be related to Homo rather than to Pan or
Gorilla. However, this assumption is not supported by many other of their features.
This paper briefly surveys the literature concerning craniodental comparisons of
australopith species with those of bonobos, common chimps, humans and gorillas, adult and
immature. It will be argued, albeit on fragmentary data, that the large australopiths of East
Africa were in many instances anatomically and therefore possibly also evolutionarily nearer
to Gorilla than to Pan or Homo, and the South African australopiths nearer to Pan and Homo
than to Gorilla. An example of a possible evolutionary tree is provided. It is suggested that
the evidence concerning the relation of the different australopithecines with humans,
chimpanzees and gorillas should be re-evaluated.
Key words: Hominid evolution, Australopithecus, robust polyphyly, gorilla, chimpanzee,
bonobo, Lucy, Taung, molecular clock.
Introduction
Biomolecular data place the Homo/Pan splitting time between 8 and 4 Myr BP (e.g. Sarich,
1977; Hasegawa et al., 1987, 1988, 1989; Caccone & Powell, 1989). This means that at the
time of the earliest undoubted australopithecines (ca. 4 Myr BP), the differences between
human and chimpanzee ancestors were much less than those between present-day Homo and
Pan, so that it is difficult to decide whether a particular fossil of that age belonged to the
Homo or to the Pan clade. No a priori reason exists therefore to reject the idea that the
African apes may have had australopith ancestors. Several people had contemplated this
possibility even before Sarich & Wilson (1967) initiated the drastic reduction of the estimated
Homo/Pan splitting time (e.g. Woodward, 1925; Smith, 1925; Keith, 1925a, b; 1931, p.115;
Schultz, 1941, p.100; A. Hrdlicka in Howells, 1985; W. Abel; W. L. Straus, S. Zuckerman, E.
H. Ashton in Reader, 1988, p. 89 and p. 124). Following the introduction of the biomolecular
evidence, the idea has revived (e.g. Kleindienst, 1975; Goodman, 1982; Gribbin & Cherfas,
1983; Hasegawa et al., 1985; Edelstein, 1987; Verhaegen, 1990; Trevino, 1991, p. 14-15).
This approach could also explain the discrepancy between the enormous number of
fossil finds and the apparent total absence of fossil African ape ancestors from a period
covering at least the last four million years (Gribbin & Cherfas, 1983; Verhaegen, 1990). The
usual explanations offered are that paleontologists have not worked in the appropriate areas,
or that the probability of fossilization in the tropical forests, where the ancestral apes
presumably lived, is very low because of the relative acidity or the wetness of the soil (e.g. G.
S. Krantz in Kleindienst, 1975). These explanations are hard to reconcile with the numerous
discoveries of forest-dwelling bovids, suids, monkeys, dryopithecines and probable early
relatives of the orang-utan (Kleindienst, 1975; Kortlandt, 1975; cf. Pilbeam, 1982; Andrews
& Cronin, 1982).
When Dart (1925) discovered the skull of Taung, he believed that it was in the human
lineage because it showed what he called “humanoid” features such as relatively small
canines and forward situation of the foramen magnum. His proposal was promptly rejected by
nearly all his colleagues (e.g. Keith, 1925a,b; Smith, 1925; Woodward, 1925; Duckworth,
1925), who saw in Taung nothing more than a sort of young chimp or perhaps gorilla. They
were supported in their opinion by the Piltdown skull, which showed a rather ape-like
dentition together with a big brain, almost the opposite of the Taung child. But later, when
Kenneth Oakley unmasked Piltdown Man as a fraud and Robert Broom concluded from his
studies of postcrania that the South African australopithecines were bipedal, opinions about
Taung changed and the australopiths became accepted as being closer to man than to apes.
This paper argues that the nearly general acceptance around 1950 of W. E. Le Gros
Clark’s ideas, following Dart and Broom, that the South African australopiths were closer to
humans than to “pongids” (mostly based on comparisons of their pelvis and dentition, often
with male gorillas, e.g. Le Gros Clark, 1978, first edition 1955) might have been an
overreaction after the unmasking of Piltdown, and that the anthropologists’ first impressions that Taung was a fossil species of Pan - should be reconsidered. (That Taung was closer to
Homo than to Gorilla and certainly Pongo, is of course not contested in this paper).
Homo-like features in australopiths: primitive?
In imitation of Dart, Broom and Le Gros Clark, the australopithecine species are now usually
considered to be closer relatives of humans than of apes. This opinion is based especially on
their locomotor and dental features.
Ventral position of foramen magnum
It is generally accepted that the australopiths were more bipedal than present-day
gorillas and common chimps, mostly because of the Laetoli footprints almost 4 Myr BP, the
short ilia of Lucy and Sts.14, the broader calcaneus and the more human-like orientations
(though rather ape-like anatomy) of the ankle and knee articulations of the Hadar specimens
(Stern & Susman, 1983; Latimer et al., 1987), and the more ventral position of the foramen
magnum in many australopiths. “Early australopithecines are linked with living humans on
the basis of shared characters related to bipedalism” (Andrews, 1992), but it is often argued
that the African apes’ ancestors also were more bipedal (theory of W. L. Straus; see Coon
1954; Kleindienst, 1975; Goodman, 1982; Gribbin & Cherfas, 1983; Hasegawa et al., 1985;
and esp. Edelstein, 1987; cf. Schultz 1949, p. 205). Indeed, that the African apes could evolve
from digiti-palmigrades (all other primates, including human infants) to knuckle-walkers
implies that they went through a phase where the arms were barely used for pronograde
locomotion (cf. Edelstein, 1987); an intermediate phase of orthograde arm-hanging or
brachiation insufficiently explains knuckle-walking since neither orangutans nor hylobatids
show traces of knuckle-walking. Also, most anthropoids (especially the young) occasionally
walk on two legs, and bipedal tendencies are very striking in the African apes (but virtually
absent in Pongo). Chimpanzee fetuses shortly before birth show humanlike feet with ventrally
oriented and adducted first digital rays (Coon, 1954). Common chimps often walk bipedally
on muddy terrain (Nishida, 1980), and bonobos are even more frequently bipedal (Zihlman et
al., 1978; De Waal, 1988). “When they are on the ground, anthropoid apes... often walk erect,
and the mountain gorilla's foot, indeed, is already similar to man’s” (Rensch, 1972, p. 63; see
also p. 130; Schultz, 1950; Edelstein, 1987). In addition, of all primates, only the African
hominoids are fully plantigrade (Gebo, 1992):
“Orangutans have further enhanced foot mobility by adapting their feet for suspension
and thus similarly utilize foot positions where the heel does not touch the substrate.
Chimpanzees and gorillas represent an alternative pattern (plantigrady), in which the
heel contacts the surface of the support at the end of the swing phase, especially during
terrestrial locomotion. Thus chimpanzees and gorillas possess feet adapted for both
arboreal and terrestrial substrates. African apes also share several osteological features
related to plantigrady and terrestrial locomotion with early hominids. Humans and
African apes are very similar in their use of plantigrady when moving or standing
upon a terrestrial substrate and this pattern of foot use is extremely different from what
characterizes all other primates”.
Also, young gorillas and chimpanzees have foramina magna more ventral than adults and well
within the range of A. africanus Sts.5 (e.g. Ashton & Zuckerman, 1952; Schultz, 1955). Even
in adults, the foramen has the same position indices in gracile (Sts.5) and robust
australopithecines (KNM-ER 406) as in bonobos (Kimbel et al., 1984, table 9). Masters et al.
(1991):
“Since Taung was perhaps 3.5 years of age at death (Bromage and Dean, 1985), the
position of the foramen magnum may not have achieved its adult status. This
contradicts the assessment made by Dart (1925), who interpreted the position of the
foramen magnum as indicating bipedal locomotion in Australopithecus africanus”.
Thick enamel
Thicker molar enamel was formerly treated as a reliable sign of affinity with the
human line, so that species such as “Ramapithecus” (now included in Sivapithecus and
usually considered to have Pongo as its closest living relative, see Pilbeam, 1982; Andrews &
Cronin, 1982) were designated as possible human ancestors on the strength of this evidence.
But this is no argument for a closer affinity of the australopithecines with humans than with
African apes, since Martin (1985) argues that the extant great apes have secondarily reduced
enamel - slight in the case of Pongo and more marked in Gorilla and Pan (but see also
Beynon et al., 1991). It is in no way inconsistent with australopiths being ancestral to African
apes (Martin, 1985):
“thick pattern 3 enamel does not identify a hominid. Moreover, the common ancestor
of the great apes and man, and of the African apes and man, would have had teeth
resembling those of hominids... Of the living members of the great ape and human
clade, only Homo sapiens retains the condition of enamel thickness and development
from the common ancestor of the clade and can therefore be regarded as the most
dentally primitive member of it”.
Smaller anterior dentition
The pronounced prognathism and large incisors and very large canines of the adult
males of G. gorilla and P. troglodytes are thought to exclude australopith ancestors, since
most robust australopiths had “flat” faces and (at least in comparison with their enormous
back teeth) small anterior teeth. But this evidence is not conclusive: (1) A. afarensis and A.
africanus also possessed moderately projecting canines, and the robust australopiths could
have been extinct side-branches specialized for extremely tough food (e.g. Verhaegen, 1992),
(2) even in robust australopiths (SK 23, Natron, L.7-125), the indices of the basic rectangle of
the mandible are within the range of these of common chimps but outside those of humans
(Kinzey, 1970); (3) in many robust specimens, the front teeth are so much worn that it is
difficult to estimate how long their unworn canines would have been (but at least the A. boisei
from Chesowanja showed unworn canines which were rather short), (4) in Gorilla and Pan
“with advancing age, canines tend to wear flat to the level of the incisors” (Ryan & Johanson.
1989); (5) bonobos “have relatively small and only slightly dimorphic canine teeth” (Zihlman
et al., 1978); (6) “infant great apes have flat or orthognathic faces like modern humans”
(Aiello & Dean, 1990, p, 197); (7) some specimens of H. erectus had maxillary diastemata of
6 mm, as large as an orang’s (Howells, 1959, p. 157; Rensch, 1972, p. 36), and much larger
than in the robust australopiths (who lived earlier); (8) selection for larger or smaller teeth can
theoretically occur in very short evolutionary periods (cf. Silson, 1988, p. 19), and is claimed
to have been demonstrated in only a few thousand years in human populations (Calcagno &
Gibson, 1988); (9) the marked difference in prognathism between Negroes and Whites (e.g.
Howells, 1959, p.269; Kinzey, 1970, fig. IA-B) developed in a time span of only about
200,000 years (Cann et al., 1987; Vigilant et al., 1991).
Moreover, it is not very likely that the primitive African hominoid condition included
ape-like pronounced prognathism and very long canine teeth. See, for instance, Kinzey’s
(1970) comparisons of the basic rectangle of the mandible in different Haplorhini (in
Kenyapithecus africanus, e.g., it resembles Homo rather than Pan), or the anatomy of the face
in infant chimpanzees (orthognathism with relatively short milk canines and vertical
mandibular symphysis).
Australopiths resemble young Pan or Gorilla
At first sight, australopith skulls are more reminiscent of African apes, especially juveniles
and subadults, than of humans (even Le Gros Clark calls them ape-like creatures): the general
morphology of the gracile crania resembles that of bonobos or common chimps, and the
larger crania are more gorilla-like (e.g. Lewin, 1987, p. 260; Zihlman et al., 1978; Rensch,
1972, p. 40; Robinson, 1960; Kennedy, 1991, fig.1). This is not contradicted by a more
detailed look at their anatomy. Table 1 gives a few striking quotations about ape-like features
of australopith skulls in general; Table 2 provides quotations about gorilla-like cranial
features in large East African fossils; Table 3, about chimpanzee-like features in africanus
and robustus crania.
It is a pity that this paper has to rely so heavily upon the anthropologists’ impressions
(quoted in Tables 1, 2 and 3), but extensive comparisons with enough species (including
several extinct hominid species, African hominoids and humans) are rather scarce. Even in
recent excellent and thorough textbooks (e.g. Conroy, 1990; Aiello & Dean, 1990),
australopith fossils are often compared only with man and one of the great apes (usually the
common chimp), and detailed comparisons of the australopithecine features with humans and
all three African ape species (not to mention orang-utans), preferably of different subspecies
(e.g. high- vs lowland gorilla), ages and sexes, are surprisingly rare in the literature (but see
e.g. Schultz, 1955; McHenry, 1983; Demes, 1988). Because of these anthropocentric
viewpoints, the differences between the African ape species - like those between the different
australopith species - are often underestimated. In fact, Pan is more closely related to Homo
than to Gorilla biochemically (see below), and Groves & Paterson (1991) in their computer
analysis of 89 anatomical features, conclude that Pan is even morphologically slightly nearer
to Homo than to Gorilla.
Table 1 - Some quotations on ape-like features in australopith crania

“The evolution of the australopithecine crania was the antithesis of the Homo line. Instead
of becoming less ape-like, as in Homo, they become more ‘ape-like’. Cranial proportions
and ectocranial features that were thought to be unique among pongids evolved separately
[? M. V.] in the australopithecines parallel [? M. V.] with the great apes. The features of
KNM-WT 17000, therefore, are not as ‘primitive’ as they look. The robust
Australopithecus did not evolve from a big-toothed pongid ancestor with large cranial
superstructures, but from a small-toothed hominid with a rounder, smoother ectocranium,
like A. africanus”. Ferguson, 1989b.











“Plio-Pleistocene hominids had markedly abbreviated [enamel] growth periods relative to
modern man, similar to those of the modem great apes”. Bromage & Dean, 1985.
“Enamel thickness has been secondarily reduced in the African apes and also, although at
a different rare and extent, in the orang-utan. Thick enamel, previously the most important
characteristic in arguments about the earliest hominid, does not therefore identify a
hominid”. Martin, 1985 (but Beynon et al., 1991).
In the South African fossils including Taung, “sulcal patterns of seven australopithecine
encocasts appear to be ape-like rather than human-like”. Falk, 1987.
“Cranial capacity, the relationship between endocast and skull, sulcal pattern, brain shape
and cranial venous sinuses, all of these features appear to be consistent with an ape-like
external cortical morphology in Hadar early hominids”. Falk, 1985.
In the type specimen of A. afarensis, “the lower third premolar of ‘A. africanus afarensis’
LH-4 is completely apelike”. Ferguson, 1987b.
“A. afarensis is much more similar cranially to the modern African apes than to modern
humans”. Schoenemann, 1989.
“Olson's assertion that the lateral inflation of the A.L. 333-45 mastoids is greater than in
any extant ape is incorrect if the fossil is compared to P. troglodytes males or some
Gorilla mates and females. Moreover, the pattern of pneumatization in A. afarensis is also
found only in the extant apes among other hominoids”. Kimbel et al., 1984.
“Prior to the identification of A. afarensis the asterionic notch was thought to characterize
only the apes among hominoids. Kimbel and Rak relate this asterionic sutural figuration to
the pattern of cranial cresting and temporal bone pneumatization shared by A. afarensis
and the extant apes”. Kimbel et al., 1984.
“... the fact that two presumed Paranthropus [robustus] skulls were furnished with high
sagittal crests implied that they had also possessed powerful occipital crests and ape-like
planum nuchale... Nuchal crests which are no more prominent - and indeed some less
prominent - will be found in many adult apes”. Zuckerman, 1954b.
In Sts.5, MLD-37/38, SK-47, SK-48, SK-83, Taung, KNM-ER 406, O.H.24 and O.H.5,
“craniometric analysis showed that they had marked similarities to those of extant
pongids. These basicranial similarities between Plio-Pleistocene hominids and extant apes
suggest that the upper respiratory systems of these groups were also alike in appearance...
Markedly flexed basicrania [are] found only in modern humans after the second year...”.
Laitman & Heimbuch, 1982.
“The total morphological pattern with regard to the nasal region of Australopithecus can
be characterized by a flat, non-protruding nasal skeleton which does not differ
qualitatively from the extant nonhuman hominoid pattern, one which is in marked contrast
to the protruding nasal skeleton of modern H. sapiens”. Franciscus & Trinkaus, 1988.
Table 2 - Quotations on gorilla-like features in large East African australopith crania
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

“Incisal dental microwear in A. afarensis is most similar to that observed in Gorilla”.
Ryan & Johanson, 1989.
The composite skull reconstructed mostly from A.L.333 specimens “looked very much
like a small female gorilla”. Johanson & Edey, 1981, p. 351.
“Other primitive [or advanced gorilla-like? M. V.] features found in KNM-WT 17000, but
not know or much discussed for A. afarensis, are: very small cranial capacity; low
posterior profile of the calvaria; nasals extended far above the frontomaxillar suture and
well onto an uninflated glabella; and extremely convex inferolateral margins of the orbits
such as found in some gorillas”. Walker et al., 1986.




As for the maximum parietal breadth and the biauriculare in O.H.5 and KNM-ER 406 “the
robust australopithecines have values near the Gorilla mean: both the pongids and the
robust australopithecines have highly pneumatized bases”. Kennedy, 1991 (see also his
fig. 1).
In O.H.5, “the curious and characteristic features of the Paranthropus skull... parallel
some of those of the gorilla”. Robinson, 1960.
The A. boisei “lineage has been characterized by sexual dimorphism of the degree seen in
modern Gorilla for the length of its known history”. Leakey & Walker, 1988.
A. boisei teeth showed “a relative absence of prism decussation”; among extant
hominoids, “Gorilla enamel showed relatively little decussation ...”. Beynon & Wood,
1986 (cf. Beynon et al., 1991).
Table 3 - Quotations on chimp-like features in South African australopith crania

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
“Alan [Walker] has analysed a number of Australopithecus robustus teeth and they fall
into the fruit-eating category. More precisely, their teeth patterns look like those of
chimpanzees... Then, when be looked at some Homo erectus teeth, be found that the
pattern changed”. Leakey, 1981, pp. 74-75.
“The ‘keystone’ nasal bone arrangement suggested as a derived diagnostic of
Paranthropus [robustus] is found in an appreciable number of pongids, particularly
clearly in some chimpanzees”. Eckhardt, 1987.
“P. paniscus provides a suitable comparison for Australopithecus [Sts.5]; they are similar
in body size, postcranial dimensions and... even in cranial and facial features”. Zihlman et
al., 1978.
“A. africanus Sts.5, which... falls well within the range of Pan troglodytes, is markedly
prognathous or hyperprognathous”". Ferguson, 1989a.
In Taung, “I see nothing in the orbits, nasal bones, and canine teeth definitely nearer to the
human condition than the corresponding parts of the skull of a modern young
chimpanzee”. Woodward, 1925.
“The Taung juvenile seems to resemble a young chimpanzee more closely than it
resembles L338y-6”, a juvenile A. boisei. Rak & Howell, 1978.
“In addition to similarities in facial remodeling it appears that Taung and Australopithecus
in general, had maturation periods similar to those of the extant chimpanzee”. Bromage,
1985.
“I estimate an adult capacity for Taung ranging from 404-420 cm2, with a mean of 412
cm2. Application of Passingham’s curve for brain development in Pan is preferable to that
for humans because (a) brain size of early hominids approximates that of chimpanzees,
and (b) the curves for brain volume relative to body weight are essentially parallel in
pongids and australopithecines, leading Hofman to conclude that ‘as with pongids, the
australopithecines probably differed only in size, not in design’”. Falk, 1987.
In Taung, “pneumatization has also extended into the zygoma and hard palate. This is
intriguing because an intrapalatal extension of the maxillary sinus has only been reported
in chimpanzees and robust australopithecines among higher primates”. Bromage & Dean,
1985.
“That the fossil ape Australopithecus [Taung] ‘is distinguished from all living apes by
the... unfused nasal bones…’ as claimed by Dart (1940), cannot be maintained in view of
the very considerable number of cases of separate nasal bones among orang-utans and
chimpanzees of ages corresponding to that of Australopithecus”. Schultz, 1941.
Only a few possibly relevant data linking an australopith fossil with one of the extant African
hominoids could be obtained from the literature (cf. Tables 2 and 3). Uniquely derived cranial
features of A. boisei and Gorilla concern: some incisal microwear features (Ryan & Johanson,
1989; though acquired ontogenetically, tooth wear reflects phylogenetic adaptations); enamel
prism decussation (Beynon & Wood, 1986; cf. Beynon et al., 1991); orbital morphology
(KNM-WT 17000, see Walker et al., 1986); body size (but see also McHenry, 1991).
Uniquely derived features of South African australopiths with Pan and Homo concern:
mandibular premolar root morphology (Wood et al., 1988; see also below). Uniquely derived
features of A. robustus and Pan concern: tooth microwear (e.g. Leakey, 1981, p.74); nasal
bone arrangement (Eckhardt, 1987); maxillary sinus topology (Bromage & Dean, 1985; see
also Cave & Wheeler Haines, 1940). Not obtained were: uniquely derived features of South
African fossils with Gorilla; of A. boisei with Pan; and of any australopith with Homo (i.e.
features that are absent from all African ape species, mature and immature). Jenkins (1991):
“Tobias (1988) prepared a comparative list of the cranial, mandibular, dental and
endocranial traits for H. habilis, A. africanus, A. robustus, and A. boisei to determine
evidence for cladogenetic relationships. His tabular summaries enumerate numerous
shared derived characters of all four taxa. However, he did not include any outgroup
comparisons. In this poster, data for two outgroups [? M. V.], composed of Gorilla
gorilla and Pan troglodytes, were compiled and compared to Tobias’ evaluations of H.
habilis, A. africanus and A. boisei. The results show that numerous traits he used are
also shared with Gorilla and Pan...”
Thick molar enamel and small anterior dentition are discussed above. Orthognathism, intermediate position of foramen magnum, relatively “short” arms, lateral plantar process of
calcaneus, longer and adducted first metatarsals, etc. are seen in bonobos or/and immature
apes. Lucy’s short ilium is not a good case: overall, her pelvis is as distinct from the human as
it is from the chimpanzee’s (e.g. Stern & Susman 1983), and the Sterkfontein Sts.14 pelvis
(notably the ischium) is even more chimp-like (Broom & Robinson, 1950; Oxnard, 1984, fig.
10.1); short ilia (in proportion to trunk length) as in monkeys and humans are probably the
ancestral condition, so that Coon (1954) could assert that, in pelvic morphology, apes look
less like monkeys than humans do (cf. Schultz, 1950, fig. 6). W. L. Straus (in Schultz, 1936,
p. 431):
“The human ilium would seem most easily derived from some primitive member of a
preanthropoid group, a form which was lacking many of the specializations, such as
reduction of the iliac tuberosity and anteacetabular spine and modification of the
articular surface, exhibited by the modern apes. I wish to emphasize here that the
anthropoid-ape type of ilium is in no sense intermediate between the human and lower
mammalian forms. Its peculiar specializations are quite as definite as those exhibited
by man, so that it appears very unlikely that a true anthropoid-ape form of ilium could
have been ancestral to the human type”.
Overall, the more human-like features of the australopith hindlimbs are less abundant than the
more ape-like features (summarized in Oxnard, 1984, Nota Bene following p. 334; and in
Verhaegen, 1990). Moreover, it has been argued that all these human-like features (e.g. the
superhumanly broad sacrum, long femoral neck and valgus knee) could have been correlated
with some sort of bipedalism in the ancestral African hominoids (see the discussion above).
With the apparent exception of the front teeth reduction and the relative orthognathism
in A. boisei and A. robustus (but juvenile African apes also are orthognathic, see Schmid &
Stratil, 1986; Aiello & Dean, 1990, p. 197), later large australopith skulls (KNM-WT 17000)
show more gorilla features than earlier ones (from A.L.333), and later smaller ones show
more chimpanzee features than earlier ones (Taung more than Sts.5, and much more than
Lucy). See, for instance, the first quotation of Table l; for KNM-WT 17000, Table 2; for
Taung, Table 3, and Falk et al. (1989); and for Lucy, Ferguson (1987b).
(The same could be true of the postcrania: see Verhaegen (1990) and the discussion of
the distal humerus below. Nevertheless, most Kromdraai and Swartkrans remains are usually
described as being intermediate between humans and chimps but more human- than ape-like
(especially the lower limb features, e.g. the adducted hallux), and more human-like than those
of Hadar (Susman, 1989; Gebo, 1992). This does not necessarily contradict the evolutionary
trees proposed in this paper: (1) although most Swartkrans fossils certainly belong to A.
robustus, a few probably represent Homo (Susman, 1989); (2) the earliest split is not that
between humans and (African) apes, but that between Pan-Homo and Gorilla (see below),
and A. robustus undoubtedly belonged to Pan-Homo rather than to Gorilla; (3) at the time of
A. robustus there already existed much more humanlike fossils (e.g. KNM ER-1470 and 148l), so that A. robustus must have belonged either to Pan or to an extinct side-branch of
Pan-Homo; (4) prenatal apes show adducted great toes (see above), and Pan (notably
paniscus) is more bipedal than Gorilla).)
In spite of the scarcity of comparative data from single sources, a few figures
regarding skulls and dentitions (the postcrania are briefly discussed in Verhaegen, 1990) are
brought together in Table 4a (comparative measurements from different sources were not
used), and some preliminary conclusions emerge from it (Table 4b):
(1) The figures of the large afarensis skulls from A.L.333 are rather ape-like, with
more bonobo-like foramen magnum indices, chimp-like frontal bone, and rather gorilla-like
dental features.
(2) Overall, A. africanus from Makapansgat and Sterkfontein resemble Pan rather than
Gorilla or Homo, and in bite force and foramen magnum indices, bonobos rather than
common chimps.
(3) The figures of A. robustus from Swartkrans, mostly regarding the dentition, are
generally intermediate between those of common chimp and gorilla.
(4) A. boisei KNM-ER 406 and O.H.5, in spite of the differences between them, are
more gorilla-like (KNM-ER 406 is even super-gorilla in bite force).
Every australopith species in this Table thus appears morphologically nearer to at least
one of the African ape species than it is to humans.
Robust polyphyly?
Biomolecular results leave no doubt that Pan is genetically closer to Homo than to Gorilla
(e.g. Goodman, 1982; Hasegawa et al., 1985, 1987, 1988; Caccone & Powell, 1989; Sibley et
al., 1990; Gonzalez et al., 1990; Ruvolo et al., 1991; Begun, 1992), and contrary to the
prevailing opinion this is not contradicted by the anatomical evidence (Groves & Paterson,
1991). This implies that the African hominoids first split into Pan-Homo (smaller, relatively
gracile) and Gorilla (larger, super-robust), and that many of the traits that common chimps
share with gorillas but not with bonobos or humans could have developed in parallel with
gorillas (e.g. very long and sexually dimorphic canines, “very” dorsal foramen magnum,
ectocranial crests, arms considerably longer than legs). Convergent and parallel, even reverse
or fluctuating evolution of anatomical traits are among the commonest features of biological
evolution (e.g. Trinkaus, 1990; Hartman, 1989; Sheldon, 1988; Seger, 1987; Gibbs & Grant,
1987; Cartmill, 1982; White & Harris, 1977; Darwin, 1903, p.171), and the final proof that
Darwinism is not a tautology. “Parallel evolution occurs when two species adopt a lifestyle
that is more or less similar. If the lifestyle is essentially identical, and the species from a
similar genetic background, the end result may be almost indistinguishable to other than
detailed examination” (R. G. Silson, pers. comm.).
The very long canines and very dorsal foramen magnum of adult gorilla and common
chimp males (but not of subadult African apes nor of adult bonobos) could well be derived
and rather recent adaptations to the same environmental (e.g. in response to climatic) changes
and cannot be explained by mere allometry. Even knuckle-walking of chimps and gorillas has
been argued to have arisen independently (Begun, 1992), possibly in more bipedal ancestors
(Kleindienst, 1975; Hasegawa et al., 1985; Edelstein, 1987). Indeed, Gorilla knuckle-walking
anatomy and ontogeny are much better developed than in Pan, and are different from Pan
(Inouye, 1992). And the LCA (the last common ancestor of Homo and Pan) had not yet
acquired knuckle-walking since humans do not at any age show the slightest trace of knucklewalking behaviour: (1) we lean (e.g. on a table) far more comfortably on our proximal than on
our middle hand phalanges; (2) whereas in knuckle-walking apes the middle hand phalanges
are naked, in many men they are dorsally haired, and fingers III and IV (that bear most weight
in knuckle-walkers) even more frequently than V and II (Harrison, 1958; Singh, 1982; Ikoma,
1986); (3) “human infants walk or run spontaneously on all fours and this invariably with the
palms flat on the ground and the fingers completely extended” (Schultz, 1936, p. 264).
Lucy’s arms were much shorter than a bonobo's (humerus 24 cm vs 29 cm; cf. 26 cm
in human pygmies) and lacked knuckle-walking adaptations (Jungers, 1982; Stern & Susman,
1982), but later the small hominid O.H.62 had more chimp- and bonobo-like proportions
(Korey, 1990; Aiello & Dean, 1990, p. 258; Wood, 1992, box 2), and the larger KNM-ER
1500 (probably a boisei female) showed some gorilla-like proportions, e.g. relatively large
forelimbs (McHenry, 1978, 1992). While the early KNM-KP 271 distal humerus was “similar
to that of modern man” (Senut, 1980; cf. Oxnard, 1984, fig.10.12; and Aiello & Dean, 1990,
p. 365 and p. 368), A. robustus TM 1517 was more chimp-like, and A. boisei KNM-ER 739
more gorilla-like (Senut, 1980; Aiello & Dean, 1990, pp. 365-368). Body weight estimations
for robustus and boisei based on formulae for ape postcrania fit much better with the massive
jaws than estimations based on human formulae (see McHenry, 1991). The boisei ulnae
O.H.36 and L.40-19 and humerus KNM-ER 739 were of gorilla robusticity and length
(McHenry, 1991, 1992; Howell & Wood, 1974; Senut, 1980; Leakey, 1971; Aiello & Dean,
1990, p. 367-369), and the curvature and the cross-section of L.40-19 are reminiscent of
knuckle-walkers (Howell & Wood, 1974); “the Rudolf australopithecines, in fact, may have
been close to the ‘knuckle-walker’ condition, not unlike the extant African apes” (Leakey,
1971). Their arm lengthening and strengthening is paralleled ontogenetically in the African
apes; Rensch (1972, p. 45) even states that “it is only after birth that an ape’s arms become
disproportionally long”, but this can only be true when arm growth relative to the height in
African apes is compared with monkeys (Schultz, 1936, fig. 15).
The possibility should be considered that robustus and boisei did not belong to the
same (robust) branch, but that their robust traits represented parallel adaptations (cf. Delson,
1987; Grine, 1987; Trinkaus, 1990; Conroy, 1990, fig. 6.40.d). Indeed, super-robust
specimens from East Africa (KNM-WT 17000) appeared in the fossil record before the less
robust A. robustus from South Africa, and the morphological differences between africanus
and robustus are less than those between robustus and boisei (e.g. Leakey, 1959, 1960; Wood,
1978; Wood & Chamberlain, 1987). This is particularly clear in dental morphology (Hunt &
Vitzthum, 1986; Wood & Uytterschaut, 1987; Wood & Engleman, 1988; Wood et al., 1988).
An analysis of root morphology in mandibular premolars, for instance, revealed moderate root
reduction in A. africanus, A. robustus and P. troglodytes, pronounced reduction in Homo but
root molarization in A. boisei compared with A. afarensis, G. gorilla and most higher primates
(Wood et al., 1988).
Possible evolutionary trees of the australopithecines are obscured by the
incompleteness of the fossil material, by parallel (e.g. boisei/robustus) or even reverse
evolution of some anatomical characters, by mosaic evolution and retention of ancestral
characters in some branches (stagnations, and “sudden” accelerations of certain features).
Nevertheless, some relationships seem to emerge (Figure 1):
(1) In East Africa, A. boisei – and perhaps some larger afarensis from A.L.333 or
Laetoli as well – is morphologically (Tables 2 and 4), and therefore probably cladistically
closer to Gorilla than to Pan or Homo. (This does not imply that some of their anatomical
features cannot be closer to humans or to chimpanzees than to gorillas. Nor that (all) gorillas
must descend from A. boisei. Biomolecular data suggest that the difference between highland
and lowland gorilla - like that between common chimp and bonobo - is less than half that
between man and chimp (Gribbin & Cherfas, 1983, p. 137), i.e. highland and lowland gorillas
possibly diverged 3-2 Myr BP. In view of the small anterior dentition of A. boisei, the
possibilities should be considered that some or all gorillas descend from a form nearer to
KNM-WT 17000 than to A. boisei, or - the prevailing opinion - that fossil ancestors of gorillas
have not been discovered yet.)
Since Homo and Pan diverged probably one or two million years later than Pan-Homo
and Gorilla (e.g. Ruvolo et al., 1991), it is not surprising that Wood (1978), in a classification
of East African fossil hominids, states that “by relying solely on morphology, the taxa
presented are most obviously subdivided into the ‘robust’ australopithecine taxon
Australopithecus boisei, and another group consisting of all the remaining taxa... In contrast
to the conformity within the ‘robust’ lineage the ‘non-robust’ hominids display a wide range
of variation”.
(2) South African australopiths (Tables 3 and 4) - and probably some very small
specimens from East Africa such as Lucy or “H. habilis” as well (cf. Zihlman, 1985;
Ferguson, 1987a,b, 1992; Wood, 1978, 1992a,b) - show more affinities with Pan-Homo than
with Gorilla. A striking example is the incus bone SK 848, which is clearly more like Homo
or Pan than like Gorilla (Rak & Clark, 1979, fig. 1). Because A. robustus lived at the time of
KNM-ER 1470 (probably an early Homo), and Taung lived even later (Partridge, 1973,
1985), they could have belonged to the Pan clade but not to the Homo clade. Taung’s
endocast, dentition, facial growth and possibly foramen magnum position strikingly resemble
those of apes and chimpanzees (Falk et al., 1989). Simons (1989):
“Dart’s enthusiasm for A. africanus as a human ancestor was occasioned by his
misidentification of the lamboid structure as the lunate sulcus and thus reading a
human-like sulcal pattern in the natural endocast of the brain of the Taung child”.
Discussion
Why are many paleoanthropologists so reluctant to consider just the possibility that some or
all of the australopithecines could have been evolutionarily nearer to one of the African apes
than to humans?
(1) When paleoanthropologists discover fossil remains, they often - understandably tend to stress the human-like features of their finds. Subsequent researchers, however,
frequently obtain more detached views.
(2) Man is often considered to possess a great number of features that are uniquely
derived from the supposed “primitive hominoid condition”: thick enamel, short canines,
forward position of the foramen magnum, short ilia, non-grasping feet, low intermembral
index, etc. But the primitive hominoid condition is largely hypothetical: as discussed above,
man seems to be more primitive in some of these features than the apes (e.g. thick enamel,
low pelvis); and in many features the differences between the ape species (e.g. between
Pongo and Gorilla) are larger than those between humans and some of the apes (e.g. relative
arm length, foot shape). Most probably the ancestral hominoids were neither like humans nor
like any of the extant ape species.
(3) In the same way, it is often uncritically accepted that the LCA was much more
chimp- than human-like. As Hasegawa et al. (1985) say:
“It is unknown whether the last common ancestor of human and chimpanzee was like
the living chimpanzee or like the living human. However it seems to have been widely
assumed implicitly that the common ancestor of the two species was more like the
chimpanzee than the human. There has been a tendency to view hominid features as
specialized and those of apes as unspecialized. Any fossil hominoids that bear some
resemblance to humans have been readily considered to be human ancestors”.
Such assumptions are reinforced by using terms like “primitive”, “plesiomorphic” or “less
advanced” (which imply that the ancestral character is known), where the more neutral
“apelike” or (if possible, and more precisely) “chimp-like”, “bonobo-like” or “gorilla-like”
would be preferable. The anthropocentric fallacy enshrined in the usage of “primitive” has
more than once been challenged (Gribbin & Cherfas, 1993; Edelstein, 1987; Verhaegen,
1990). Since homoplasy, convergence, and reverse (and even fluctuating) evolution are so
common, ontogeny may provide more reliable criteria to decide what is primitive (Trinkaus,
1990; cf. Northcutt, 1990). “Morphological characters can be subjected to parallel or
convergent evolution, and cannot be used with confidence for phylogenetic reconstructions
unless the probability of parallel evolution is evaluated or rejected in a proper way”
(Hasegawa et al., 1987).
As we go further back in time, we may expect that human ancestors become more
chimpanzee-like, but also that the chimpanzees’ ancestors become more human-like, i.e.
display a few human-like features. Assuming that the LCA looked much more like a
chimpanzee than a human and that subsequently humans have evolved much more than
common chimps is statistically less likely than assuming that the LCA already possessed a
few mosaic human-like features (e.g. facultative bipedalism, orthognathism, thicker enamel)
and that both branches (Homo and Pan) underwent evolutionary changes towards their
present-day representants (e.g. much longer legs in humans, longer arms in chimps). In fact, it
seems most economical to assume that the LCA 8-4 Myr BP looked somewhat like bonobos
(or like subadult chimpanzees), which are in several instances - but not, for instance, in body
weight - intermediate between humans and common chimps, e.g. in relative canine size,
canine dimorphism, orthognathisrn, foramen magnum indices, relative arm and leg lengths,
bipedalism and knuckle-walking. Although the LCA lived earlier, the gracile australopiths of
3-2.5 Myr BP (Lucy, Sterkfontein) are the best approximation we presently have: see Aiello
& Dean (1990, p. 254), or in Table 3 the quotation of Zihlman et al. (1978).
It seems that, while our ancestors were becoming more and more human-like, the
African apes - at first the ancestor of the gorillas and shortly thereafter that of both
chimpanzees - for unknown reasons (climatic and habitat changes?) - broke away from our
evolutionary direction, partially reversed their evolution, and became again - the three species
to different degrees - more like monkeys in thinner enamel, larger front teeth, prognathism,
ectocranial crests, relatively smaller endocast, more dorsal foramen magnum, elongated iliac
blades, short femoral necks, less valgus knees, more grasping feet, quadrupedalism, etc. (but
not, for instance, in body size, relative arm length, knuckle-walking, pelvic height, number of
lumbar, sacral and coccygal vertebrae).
There are admittedly several weak spots in this scenario: the many reversals (notably
in the lower limb anatomy) and parallelisms (e.g. anterior dentition, iliac anatomy, knucklewalking adaptations) in the evolution of Gorilla and Pan. (If Pongo is included in the
comparison, even more - apparently improbable - parallelisms are needed, although, as
discussed above, for most of such features (e.g. sexual dimorphism, foramen magnum
position, relative arm length, foot shape), at least one African ape species can be found to be
more different from orangs than from humans, and Andrews (1992), in a review of Miocene
hominoids, even asserts that “if Sivapithecus belongs in the orangutan clade, as I have argued,
the shared [postcranial] morphology of the orang-utan and the African apes must have arisen
independently”).
However, if these reversals and parallelisms are correlated (re-adaptations to, for
instance, an older, less “innovating” or less human-like lifestyle or environment), the counterargument to my scenario fails. Moreover, the traditional hypothesis - that all
australopithecines are more closely related to humans than to African apes - seems to have
more serious difficulties, since it does not explain: (1) the apparent complete absence of fossil
ancestors or relatives of any African ape; (2) the various australopith-like features that are
present in premature though not in adult African apes (e.g. orthognathy, less dorsal foramen
magnum, more humanlike feet); (3) the fact that all australopiths lack the uniquely derived
bony features which set man (at least since H. erectus) clearly apart from the other catarrhines
(e.g. external nose, very large brain, very long legs), and that they resemble the apes in these
respects; (4) that every one of the australopith species has more features in common with
either gorillas or chimpanzees than with humans (e.g. Tables 2, 3 and 4); (5) and that at the
time of the robust australopiths there already lived more humanlike creatures (KNM-ER
1470).
(Oxnard’s (1984, p. 307-332) proposition - that the australopiths were evolutionarily
nearly equidistant from African apes and humans and left no descendants today - does not
have the fifth difficulty. Also, in my opinion, Oxnard correctly states that many australopith
postcrania were biomechanically unique, and could have represented adaptations to a welldefined lifestyle (e.g. Verhaegen, 1992).)
Conclusion
A review of the paleo-anthropological literature reveals no data that exclude the possibility
that both gorillas and chimpanzees could have had australopith ancestors. Bipedalism is
generally considered to be the shared feature that links australopithecines with humans, and
there is no doubt that at least some of the australopith species were partial bipeds. But it has
never been proven that the African apes’ unique locomotion (plantigrade knuckle-walking)
could not have evolved from some kind of (“short”-legged) bipedalism. In fact, insofar as the
fragmentary fossil material and the incomplete comparisons with extant apes allow,
ontogenetic and morphological evidence tends to favour the hypothesis that the last common
ancestor of Homo and Pan 8-4 Myr BP was a partially bipedal, gracile australopith with
chiefly a mosaic of human and chimpanzee (esp. bonobo) features: low sexual dimorphism,
minimal prognathism, slightly enlarged canines, non-protruding nasal skeleton, smooth
ectocranium without crests, “small” brain with ape-like sulcal pattern, relatively non-flexed
basicranium, intermediate position of foramen magnum, “short” forelimbs without knucklewalking features, low ilia, (very) long femoral necks, “short” legs, (very) valgus knees, full
plantigrady, longer and not very abductable halluces.
I expect that when australopith fossil material is re-examined and compared in detail
with every one of the large hominoids, in most cases it will resemble either Pan or Gorilla
more closely than it resembles Homo and certainly Pongo.
ACKNOWLEDGMENTS – I wish to thank A. S. Ryan, M. Goodman, M. Hasegawa, R. G. Silson,
M. R. Kleindienst, E. Morgan and especially J. Verhulst for their corrections and comments
on various versions of this manuscript.
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Table 4A - Measurements of australopithecine, African ape and human skulls
foramen magnum indicesa
- basion I
- basion II
- opisthion I
- opistbion II
333-45
(51.4)
(77.2)
(15.9)
(21.3)
Sts.5
43.7
66.2
(14.2)
(19.4)
frontal bene indicesb
- B at post-orb.constrict.(mm)
- minimum frontal B (mm)
- fronto-temporal B index
- superior facial B (mm)
- inner biorbital B (mm)
- fronto-facial B index
- fronto-biorbital B index
recon.
66.0
107.0
94.0
62.0
78.6
Sts.5
64.0
48.0
75.0
93.5
84.2
68.4
76.0
rel.H ant.masseter originc
- zygomax.-alveolar margin
- orbitoalveolar H
- zm-alv/lorb-alv.index
recon.
24.0
(47.5)
50. 5
mandibulad
- ramus H (mm)
- ramus B (mm)
- H/B %
recon.
55.0
55.0
100.0
mandibular fossa e
- L (mm)
- B (mm)
- D (mm)
- L/B %
- D/L %
- D/B %
bite forcef
- infratemporal fossa (cm²)
- molar crown are (cm²)
- bite force equivalent M²
- bite force equivalent at I
recon.
(16.0)
5.38
13.9
9.2
incisal microwearg
- wear striae (/mm²)
- pits (/mm²)
- pit diameter (mm)
- wear striation orientation
A.afar.
4.40
2.17
.07
61°
O.H.5
54.9
69.3
27.6
33.3
ER-406
40.5
(57.1)
15.6
(20.6)
SK-48
(67.0)
(27.0)
40.3
(100.0)
(93.0)
65.7
72.0
O.H.5
69.4
(25.0)
36.0
115.5
97.0
60.3
71.5
ER-406
62.0
31.0
50.0
114.0
100.0
54.4
62.0
Gorilla
69.0
44.2
64.1
125.3
105.1
55.5
66.0
Pt
70.5
54.7
77.4
106.2
90.0
66.6
78.4
Peking
96.0
86.0
89.6
121.0
111.0
79.3
86.5
Sts.5
32.0
51.0
62.7
SK-48
38.3
61.0
62.8
O.H.5
36.0
75.1
47.9
ER-406
40.0
62.0
64.5
Gorilla
36.4
71.3
51.2
Pt
24.6
51.2
48.0
Homo
18.1
41.3
43.8
Sts.7
61.0
46.8
130.0
SK
60.7
54.5
111.4
O.H.5
65.0
-
Natron
47.0
52.8
89.0
Gorilla
67.0
62.5
108.0
Pt
43.1
46.4
92.9
Homo
35.9
37.4
94.7
MLD
22.7
30.4
7.8
74.6
34.2
25.5
A.rob.
26.7
31.9
9.5
83.5
35.8
29.8
O.H.5
27.8
34.4
8.7
81.1
31.2
25.2
G male
27
46
10
58.7
37.1
22.1
Pt male
25
29
7
86.3
27.9
24.1
Homo
25.0
23.8
14.5
99.0
61.4
60.8
Sts.5
9.7
5.87
7.8
5.3
SK-48
(11.0)
5.73
12.2
9.O
Gorilla
17.5
6.42
15.6
9.4
Pt
12.7
3.53
10.9
6.5
Gorilla
3.02
1.87
.06
60°
Pt
5.27
3.87
.06
37°
ER-406
18.3
8.92
18.0
12.0
Pt
33.3
52.0
11.2
16.2
Pp
41.6
61.3
16.3
22.1
Pp
7.5
2.45
6.6
3.9
Peking
81.1
87.2
31.8
33.5
Homo
7.2
2.86
6.7
4.3
Eskimo
6.85
2.17
.18
17°
Table 4A-4B - Legend
H human(like); Pt common chimp(like); Pp pygmy chimp(like); G gorilla(like); G>P, P>G apelike;
Pp? like Pt, but possibly even more like Pp (no figures available for Pp);
+ very much like ... ; - well outside African hominoid range;
B breadth; D depth; H height; L length;
recon. reconstruction of large A.afarensis; 333-45 large A.afarensis from A.L.333-45;
Sts.5, Sts.7 A.africanus from Sterkfontein; MLD A.africanus MLD-37138 from Makapansgat;
SK mean of A.robustus SK-12, SK-23 and SK-34 from Swartkrans;
O.H.5, ER-406 A.boisoi from Olduvai and Turkana; Natron from Peninj River;
Peking H.erectus; Eskimo H.sapiens.
In extant hominoids, measurements are means of males and females, unless mentioned otherwise.
a
e
b
f
Kimbel et al., 1984, table 9
ibid., table 6
c
ibid., table 5
d
ibid., table 2
Tobias, 1968, table 1
Demes & Creel, 1988, table 1 and 2
g
Ryan et al., 1989, table 21
Table 4B - Australopiths compared with African hominoids
foramen magnum indicesa
- basion I
- basion II
- opisthion I
- opistbion II
333-45 Sts.5
Pp
Pp+
He
Pp
Pp+ Pp
Pp+ Pp>Pt
frontal bene indicesb
- B at post-orb.constriction
- minimum frontal B (mm)
- fronto-temporal B index
- superior facial B (mm)
- inner biorbital B (mm)
- fronto-facial B index
- fronto-biorbital B index
recon. Sts.5 SK-48 O.H.5 ER-406
G>P G>P G>P+ G>P+ G>P
G>P GGGP+
GGGP+
Pp? P
H>PG H>PG
Pp? Pp? P
P>G G>P
P+
P+
G>P G>P G+
(Pp??)
rel.H ant.masseter originc
- zygomax.-alveolar margin
- orbitoalveolar H
- zm-alv/lorb-alv.index
recon.
P+
P
G+
(Pp?)
mandibulad
- ramus H (mm)
- ramus B (mm)
- H/B %
recon. Sts.7
G>P G
G>P P+
H>PG G-
mandibular fossa e
- L (mm)
- B (mm)
- D (mm)
- L/B %
- D/L %
- D/B %
Sts.5
G>P
P+
G>P-
O.H.5
Pp
Pp
He
He+
SK-48
G+
P>G
G>P-
0.H.5
G+
G
P+
ER-406
Pp+
Pp>Pt
Pp+
Pp
ER-406
GG>P
G>P-
SK
0.H.5 Natron
G
G+
P
G>P
P>G
G+
P>H
MLD A.rob. O.H.5
H=P G
G
P+
P+
P
P
G+
G>P
P
P+
P
G>P+ G+
P
P>G+ P>G+ P>G+
bite forcef
- infratemporal fossa (cm²)
- molar crown area (cm²)
- bite force equivalent M²
- bite force equivalent at I
recon.
G
G
G
G+
incisal microwearg
- wear striae (/mm²)
- pits (/mm²)
- pit diameter (mm)
- wear striation orientation
A.afar.
P>G
H+
G>P+
G+
Sts.5
Pp>t
G
HP
H>P
SK-48
Pt
G
Pt>G
G+
(Gorilla??)
(Pp??)
(Pp??)
ER-406
G+
GG
G-
(all)
(Pp??)
Figure 1 - An example of a possible evolutionary tree of fossil hominids
0 Myr BP
Gg
:
:
:
?
1
2
3
4
Ab
Ab
Ab
Ab
Pt
:
:
:
:
?
Ar
Ar
Pp
:
:
:
:
:
?
O.H.62
.
.
WT-17000
:
:
?A.L.333
:
:
?Laetoli
Hs
:
Hn
He
He
He
He
He
.
. ?ER-1470
.
.
.
At ?
At ?
?Lucy
.
.
?BC-1
.
.
Gorilla gorilla
Pt Pan troglodytes
Pp Pan paniscus
Ab Australopithecus boisei
Ar A. robustus
At A. africanus transvaalensis
He Homo erectus
Hn Homo neanderthalensis
Hs Homo sapiens sapiens
DID ROBUST AUSTRALOPITHECINES PARTLY FEED ON HARD PARTS OF GRAMINEAE?
Human Evolution 7: 63-64, 1992
Estimates of bite force suggest that Paranthropus boisei and P. robustus fed on “low-energy
food that had to be processed in great quantities”, “a hard object diet”, “food objects... hard
and round in shape” (Demes & Creel, 1988). According to studies on molar enamel
microwear of South African australopithecines, “Paranthropus ate substantially more hard
food items than Australopithecus” (Grine & Kay, 1988). Studies on incisal microwear
suggest that “P. robustus may have ingested foods that required less extensive incisal
preparation than the foods consumed by A. africanus” (Ungar & Grine, 1991), but “incisors
need not be employed in the manipulation of hard objects” (Ungar & Grine, 1989). However,
the precise nature of the robust australopithecine diet is still unknown.
A solution may be found in the remarkable parallelism between the dentitions of
robust australopithecines, especially P. boisei, and the giant panda, Ailuropoda melanoleuca.
In comparison with respectively non-robust australopithecines and non-panda bears, both
have less prognathic faces, relatively smaller incisors and canine teeth, broader and heavier
cheek bones, broader molars and premolars and “molarized” premolars, and thicker molar and
premolar enamel (Aiello & Dean, 1990; Du Brul, 1977; Grassé, 1955). The heavy grinding
apparatus of P. boisei could have been an adaptation for processing, among other things,
tough parts of bamboo plants, on which giant pandas almost exclusively feed. The stalks of
bamboo and other Gramineae such as sugar cane fit the description of low-energy food as
well as that of hard and round food objects.
P. boisei has been discovered in former lagoons (Carney et al., 1971) and montane
forests (Bonnefille, 1976), and P. robustus, near streamside or marsh vegetations (Brain,
1981, p. 189). In such environments the bamboo or reed species on which some primates feed
are abundant (e.g. MacKinnon, 1978; Glander et al., 1989).
This diet is not as unlikely for a hominid as it may seem. Humans eat grains of
different Gramineae (rice, com, wheat), and our closest relatives are known to feed also on
harder parts of Gramineae: common chimpanzees like to chew sugar cane stalks, and young
mountain gorillas love the young shoots of bamboo while the adult males crack the stalks of
bamboo (MacKinnon, 1978). Other primates that cat different parts of bamboo are
Rhinopithecus roxellana, Cercopithecus mitus kanditi, Callicebus moloch and three
Hapalemur species (Glander et al., 1989). An electron microscope study of the enamel
surface of the teeth of Gigantopithecus blacki indicates that also this fossil ape, which
developed thick enamel and strongly molarized premolars in parallel with the robust
australopithecines, fed partly on Gramineae, possibly bamboo (Ciochon et al., 1990).
It must be possible to test this hypothesis by comparing molar enamel microwear of
Gigantopithecus, Paranthropus and Ailuropoda.
References
Aiello L. & Dean C., 1990. Human Evolutionary Anatomy, Academic Press, London.
Bonnefille R., 1976. Implications of pollen assemblage from Koobi Fora Formation, East
Rudolf Kenya. Nature, 264: 403-407.
Brain C. K., 1981. The hunters or the hunted? University of Chicago Press, Chicago.
Carney J., Hill A., Miller J. A. & Walker A., 1971. Late australopithecine from Baringo
District, Kenya. Nature 230: 509-514.
Ciochon R. L., Piperno D. & Thompson R. G., 1990. Opal phytoliths on the teeth of the
extinct ape Gigantopithecus blacki: implications for paleodietary studies. Proceedings
of the National Academy of Sciences USA, 87: 8120-8124.
Demes B. & Creel N., 1988. Bite force, diet, and cranial morphology of fossil hominids.
Journal of Human Evolution, 17: 657-670.
Du Brul E. L., 1977. Early hominid feeding mechanisms. American Journal of Physical
Anthropology, 47: 305- 320.
Glander K. E., Wright P. C., Seigler D. S., Randrianasolo V. & Randrianasolo B., 1989.
Consumption of cyanogenic bamboo by a newly discovered species of bamboo lemur.
American Journal of Primatology, 19: 119-124.
Grassé P. P., 1955. Traité de Zoologie, Masson & Cie, Paris, Vol. 1 7.
Grine F. E. & Kay R. F., 1988. Early hominid diets from quantitative image analysis of dental
microwear. Nature, 333: 765-768.
MacKinnon J. R., 1978. The ape within us, Collins, London.
Ungar P. S. & Grine F. E., 1989. Maxillary central incisor wear in Australopithecus and
Paranthropus. American Journal of Physical Anthropology, 78: 317.
Ungar P. S. & Grine F. E., 1991. Incisor size and wear in Australopithecus africanus and
Paranthropus robustus. Journal of Human Evolution, 20: 313-340.
AFRICAN APE ANCESTRY
Human Evolution 5: 295-297, 1990
It is commonly believed that the australopithecines are more closely related to humans than to
African apes. This view is hardly compatible with the biomolecular data, which place the
Homo/Pan split at the beginning of the australopithecine period. Nothing in the fossil hominid
morphology precludes the possibility that some australopithecines were ancestral to gorillas
or chimpanzees and others to humans.
Key words: Hominid evolution, gorilla, chimpanzee, Australopithecus, Lucy, Taung.
It is commonly thought that from a period covering at least the last four million years, no
fossils of ancestors of the African apes have been found so far, although hundreds of hominid
fossils have been discovered from that period. The usual explanation for this remarkable
absence of fossil apes is low fossilisation probability in tropical forests (where the ancestral
apes presumably lived).
A more likely solution is that not only man, but also the African apes have descended
from the australopithecines (e.g., Gribbin & Cherfas, 1983; Hasegawa et al., 1985; Edelstein,
1987). The molecular clock leaves little doubt that the man/chimp split occurred between 6
and 4 Myr BP (Hasegawa et al., 1985), which is in the beginning of the australopith period
from about 6 (Lukeino, Lothagam) until 1 Myr BP (Taung).
Australopithecines are generally believed to be closer to man than to apes because of
their dental and locomotor features. Like man, they have much thicker molar enamel than
apes, but enamel thickness has been secondarily reduced in the African apes (Martin, 1987).
The robust forms show much smaller anterior teeth than the adult males of G. gorilla and P.
troglodytes (differences with the females are less). But bonobos have rather small and only
slightly dimorphic canine teeth (Zihlman et al., 1978). Since the prognathism of Negroes
compared with other humans developed in about 200,000 years (Cann et al., 1987), the
evolution of the (indeed much more pronounced) ape prognathism in 1 Myr cannot be
considered impossible.
The humanlike orientations of afarensis, distal femoral and tibial articulations (Stern
& Susman, 1983), the short iliac bones of Lucy and A. africanus (McHenry, 1982), and the
more central foramen magnum in the robust australopiths and Taung are thought to be
correlated with bipedality. However, Gribbin & Cherfas (1983), Hasegawa et al. (1985) and
Edelstein (1987) have argued that the African apes’ ancestors were more bipedal. Also
bonobos have a more central foramen (Kimbel et al., 1984) and frequently walk bipedally
(Zihlman et al., 1978).
The mistake of many palaeoanthropologists - the anthropocentric fallacy using
«primitive» for «gorilla-» or «chimp-like» - is described by Hasegawa et al. (1985): «It seems
to have been widely assumed implicitly that the common ancestor (of man and chimp) was
more like the chimpanzee».
Cranial resemblances between australopithecines and apes are listed in Table 1. Also
«the Homo like features of Australopithecine limb bones tend to have been greatly
exaggerated in the literature (O. J. Lewis, pers. comm.). Most afarensis postcranials (AL 288,
129, 333) are different from both humans and apes, but the scapula, humerus, ulna, knee,
hand and foot bones are more like apes (McHenry, 1982; Stern & Susman, 1983; Senut, 1981;
Feldesman, 1982; Tardieu, 1986; Sarmiento, 1987; Deloison, 1985).
Lucy’s pelvic girdle AL 288 resembles the apes in some respects (lateral enlargement
of iliac blades, small auricular and acetabular articulation surfaces, small lumbosacral angle;
McHenry, 1982; Stern & Susman, 1983; Abitbol, 1987), and her upper limb looks rather
bonobo-like (Stern & Susman, 1983; Feldesman, 1982). Also A. africanus scapula Sts 7
(McHenry, 1982), its hand bones (TM 1526) and those of A. robustus (SKW 14147, SK 84
and 85) are more chimp than humanlike (Lewis, 1977). The enormous L40-19 ulna of A.
boisei is of gorilla size, and morphologically intermediate between man and common chimp
(Feldesman, 1982).
Although the picture is confused by the retention of ancestral characters in populations
that split not very long before (e.g., large and small A. afarensis) and by parallel evolution
(both robust forms lived at the same time), it gives me the following impressions. A. boisei
and perhaps some of the larger A. afarensis are closer to Gorilla, while Lucy and the South
African australopiths show more affinities with Homo-Pan (but A. robustus, living at the time
of KNM-ER 1470, could not belong to the Homo lineage). The Taung child, which lived even
later than A. robustus, is perhaps ancestral to Pan paniscus or to Pan troglodytes.
Table l - Cranial resemblances of australopiths with apes










The australopith dentition is more apelike in development pattern (Conroy & Vannier,
1987), enamel growth rate (Bromage & Dean, 1985), dental morphology (Johanson &
Edey, 1981), and enamel microwear.
All australopithecine brain endocasts appear to be ape rather than humanlike in size and
sulcal pattern (Falk, 1985).
The composite A. afarensis skull (mostly AL 333; Kimbel et al., 1984) «looked very
much like a small female gorilla» (Johanson & Edey, 1981).
The extensive pneumatization of the AL 333-45 temporal bone is also seen in chimpanzee
males and some gorillas; «the pattern of pneumatization in A. afarensis is also found only
in the extant apes among other hominoids» (Kimbel et al., 1984).
KNM-WT 17000 had «extremely convex inferolateral margins of the orbits such as found
in some gorillas» (Walker et al., 1986).
«The ‘keystone’ nasal bone arrangement suggested as a derived pattern diagnostic of
Paranthropus is found in an appreciable number of pongids, particularly clearly in some
chimpanzees» (Eckhardt, 1987).
A. robustus incus SK 848 resembles Pan more than Homo and certainly than Gorilla (Fig.
1 in Rak & Clarke, 1979).
A. africanus Sts 5 resembles a bonobo skull (Zihlman et al., 1978).
The Taung skull has much more chimp than human traits (Bromage, 1985) and is indeed
much too recent (Partridge, 1985) to be on the line to Homo.
Its «pneumatization has also extended into the zygoma and hard palate. This is intriguing
because an intrapalatal extension of the maxillary sinus has only been reported in
chimpanzees and robust australopithecines among higher primates» (Conroy & Vannier,
1987).
References
Abitbol M. M., 1987. Evolution of the lumbosacral angle. American Journal of Physical
Anthropology, 72: 361-372.
Bromage T. G., 1985. Taung facial remodeling: a growth and development study. In: P. V.
Tobias, ed. Hominid Evolution, pp. 239-245, Liss, New York.
Bromage T. G. & Dean M. C., 1985. Re-evaluation of age at death of immature fossil
hominids. Nature, 317: 525-527.
Cann R. L., Stoneking M. & Wilson A. C., 1987. Mitochondrial DNA and human evolution.
Nature, 325: 31-36.
Conroy G. C. & Vannier M.W., 1987. Dental development of toe Taung skull from computed
tomography. Nature, 329: 625-627.
Deloison Y., 1985. Comparative study of calcanei of primates and Pan-AustralopithecusHomo relationships. In: P. V. Tobias, ed. Hominid Evolution, pp. 143-147, Liss, New
York.
Eckhardt R.B. Hominoid nasal region polymorphism and its phylogenetic significance.
Nature, 328: 333-335.
Edelstein S. J., 1987. An alternative paradigm for hominoid evolution. Human Evolution, 2:
169-174.
Falk D., 1985. Hadar AL 162-28 endocast as evidence that brain enlargement preceded
cortical reorganization in hominid evolution. Nature, 313: 45-47.
Feldesman M. R., 1982. Morphometrics of the ulna of some Cenozoic «hominoids». American
Journal of Anthropology, 57: 187.
Gribbin J. & Cherfas J., 1983. The monkey puzzle, Triad, Paladin.
Hasegawa M., Kishino H, & Yano T., 1985. Dating of the human-ape splitting by a molecular
clock of mitochondrial DNA. Journal of Molecular Evolution, 22: 160-174.
Johanson D. C. & Edey M. A., 1981. Lucy, Granada, London.
Kimbel W. H., White T. D. & Johanson D. C., 1984. Cranial morphology of Australopithecus
afarensis: a comparative study based on a composite reconstruction of toe adult skull.
American Journal of Physical Anthropology, 64: 337-388.
Lewis O. J., 1977. Joint remodelling and the evolution of the human hand. Journal of
Anatomy, 123: 157-201.
Martin L., 1987. Significance of enamel thickness in hominoid evolution. Nature, 314: 260263.
McHenry H. M., 1982. The first bipeds: a comparison of the A. afarensis and A. africanus
postcranium and implications for toe evolution of bipedalism. Journal of Human
Evolution, 15: 177-191.
Partridge T. C., 1985. Spring flow and tufa accretion at Taung. In: P. V. Tobias, ed. Hominid
Evolution, pp. 171-187, Liss, New York.
Rak Y. & Clarke R. J., 1979. Ear ossicle of Australopithecus robustus. Nature, 279: 62-63.
Sarmiento E. E., 1987. Long bone torsions of the lower limb and its bearing upon the
locomotor behavior of australopithecines. American journal of Physical
Anthropology, 72: 250-251.
Senut B., 1981. Humeral outlines in some hominoid primates and in Pliopleistocene
hominids. American journal of Physical Anthropology, 56: 257-283.
Stern J. T. & Susman R. L., 1983. The locomotor anatomy of Australopithecus afarensis.
American Journal of Physical Anthropology, 60: 279-317.
Tardieu C., 1986. The knee joint in three hominid primates: application to Plio-Pleistocene
hominids and evolutionary implications. In: D. M. Taub & F. A. King, eds. Current
Perspectives in primate Biology, pp. 182-192, Van Nostrand Reinhold, New York.
Walker A., Leakey R. E., Harris J. M. & Brown F. H., 1986. 2.5-Myr Australopithecus boisei
from west of Lake Turkana, Kenya. Nature, 322: 517-522.
Zihlman A.L., Cronin J. E., Cramer D. L. & Sarich V. M., 1978. Pygmy chimpanzee as a
possible prototype for the common ancestor of humans, chimpanzees and gorillas.
Nature, 275: 744-746.
LETTER TO THE EDITOR
Human Evolution 2: 381, 1987
Sir,
The aquatic ape theory states that our hominid ancestors spent a considerable part of
their day swimming end diving in a river, lake or sea, and, at least partially, are aquatic food.
The AAT is supported by our lack of body hair, our thick fat-layer and several other features
absent in nonhuman primates, but widespread among aquatic mammals (HARDY, 1960;
MORGAN, 1982; VERHAEGEN, 1985).
The ability to speak is a uniquely human character. Innumerable attempts explaining it
have been made, but the question how language emerged has not yet been solved. Recently it
has been suggested that the origin of speech was facilitated by our aquatic past (MORGAN,
1982, pp. 92-105; MORGAN & VERHAEGEN, 1986). All aquatic mammals control their
breathing «voluntarily», i.e. through the primary motor cortex. When surfaced they open the
airway whenever they went to inhale air, and they can hyperventilate and then close the
airway whenever they intend to dive.
The human primary motor cortex (area 4) is much larger than that of apes, mostly due
to the expansion of the areas for the musculature of mouth, throat end breathing. Just in front
of that enlarged area 4 lies the typically human Broca’s area. In present-day man, it
coordinates the activities of the enlarged area 4, to produce the right sound on the right time.
Brcoca’s area may have been originated in a previous aquatic phase to coordinate the muscles
commanded by the enlarged area 4, to make the right airway muscle contract on the right
time: just before, during or just after a dive. In order to use this voluntary control for
improving his vocalizations, our ancestor must have been able to interpret his own sound
production (feedback). This was improved by the evolution of the arcuate fasciculus, a
typically human pathway between Broca’s area end Wernicke’s area (GESCHWIND, 1972).
Wernicke’s area, a primary language area used for decoding spoken language, lies dorsal to
primary auditory cortex end to the principal sensory areas for mouth end throat. In
Wernicke’s area, connections could be made with other nearby association trees, and a certain
sound or combination of sounds could be associated with something that our ancestor was
aware of (hearing, seeing, feeling, doing) at the same time. Compared with a chimp’s brain
our association areas are enormously enlarged. These areas amplified the possibilities of the
sound producing apparatus: they act as the hardware of the computer, whereas the sound
analysing end producing areas act as the input/output apparatus; the particular language is the
software.
Most authors discussing language origins try to explain our speech capacity by an
enormous improvement of vocalizing abilities that already existed in rudimentary form in
prehuman primates, but fail to explain how exactly this could have occurred. In my opinion,
most of these problems are readily solved by the application of the aquatic theory to the vocal
and breathing apparatus.
GESCHWIND N., 1972. Language and the brain. Scient. Amer., 226: 76-83.
HARDY A. C., 1960. Was man more aquatic in the past? New Scient., 7: 642-5.
MORGAN E., 1982. The aquatic ape. London: Souvenir.
MORGAN E. & VERHAEGEN M., 1986. In the beginning was the water. New Scient., 1498: 6263.
VERHAEGEN M., 1985. The aquatic ape theory: evidence and a possible scenario. Med.
Hypoth., 16: 16-32.