ARE HUMAN BEINGS APES, OR
ARE APES PEOPLE TOO?
Russell H. Tuttle*
1. INTRODUCTION
We do not know how many genes mark levels of separation among apes and people; we
cannot discretely recognize their phenotypic expressions; and they probably are not of
equal value to sort apes from people and apes from other apes. Until the developmental
and functional biology of our genomes are much better understood (Naylor and Brown,
1998; Hamdi et al., 1999), I recommend a measure of dispassionate conservatism among
colleagues who would resolve puzzles regarding our bushy phylogeny and the largely
uncharted lineages of extant apes.
Estimates of the number of genes in the human genome and presumably also in those
of chimpanzees and other great apes range between 30,000 and 150,000 (Venter et al.,
2001; Claverie, 2001; Cohen, 1997; Fields et al., 1994; Hattori et al., 2000; O’Brien et al.,
1999; Reeves, 2000). Accordingly, if humans and chimpanzees share 98.4% of their genes,
between 480 and 2400 of them could be different. However, if Britten (2002) is correct
that the overall difference is 5%, then there are 1500–7500 different genes. And if the
human-chimpanzee difference in DNA is has been underestimated “possibly by more than
a factor of 2” (Britten et al., 2003, p. 4664), the difference could be more than 3000–
15,000 genes. Currently, we are poorly equipped to state how many of these genes, in
what combinations, and how interacting with the several pre- and postpartum environments
that shape organisms throughout their careers might be determinate in gauging the distances
among them following furcation of the human lineage, whether it be from a dichotomy of
humans and chimpanzee/bonobos (Bailey et al., 1992; Diamond, 1988; Horai et al., 1995;
Ruvolo, 1996; Goodman et al., 1998), a tritomy of African apes and humans (Marks, 1995;
Deinard and Kidd, 1999; Samollow et al., 1996; Rogers, 1994), or a polytomy that also
included extinct collateral lineages for which there is no genetic material (Corruccini,
1994).
* Russell H. Tuttle, Department of Anthropology, The University of Chicago, 1126 E. 59th Street, Chicago, IL
60637-1614, USA.
In Human Origins and Environmental Backgrounds. 2006. Edited by Hidemi Ishida,
Russell H. Tuttle, Martin Pickford, Masato Nakatsukasa and Naomichi Ogihara.
New York: Springer.
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2. FAMILY MATTERS
Contrary to Begun’s (1999) proclaimed near-consensus that all extant apes and humans
are cofamilially Hominidae, I maintain that restriction of the Hominidae for modern humans
and our bipedal Plio-Pleistocene ancestors and collateral bipedal species should be
maintained at least until the functional meanings of genomic variations among apes and
people can be explicated.
Mayr (1969: 94) defined family as “a taxonomic category containing a single genus or
a monophyletic group of genera, which is separated from other families by a decided gap”
and “recommended...that the size of the gap be in inverse ratio to the size of the family.”
Granted that the overall point-genetic distance of humans from apes, particularly the
African ones, is relatively small, the number of species in the Hominidae should be sizeable
in order for a traditional familial status to be sustained. The current inclusion of at least 16
Plio-Pleistocene species (Tattersall, 2000) with Homo sapiens in a common higher taxon
argues for Hominidae sensu stricto, with Pongo pygmaeus, P. abelii, Gorilla gorilla, G.
beringei, Pan troglodytes, Pan paniscus (Grubb et al., 2003), and the 12 species of gibbons
(Brandon-Jones et al., 2004) relegated to other families. Therefore, I recommend that the
Hominidae comprise species of Homo, Australopithecus, and Paranthropus and
provisionally Ardipithecus, Kenyanthropus, Sahelanthropus, and Orrorin and that Pan,
Gorilla, and their Miocene-Pleistocene ancestors constitute the Panidae. Pongidae would
include only Pongo pygmaeus and P. abelii among extant apes plus fossil species that are
closely related to them, and the 12 species of gibbons and their ancestors constitute the
Hylobatidae (Table 1).
3. HOMINIDAE
There are distinctive features of the pelvic girdle, lower limb, and lumbar spine that identify
a hominoid as being terrestrially bipedal. They allow identification of Hominidae sensu
stricto in Plio-Pleistocene deposits, and one hopes that soon they will be traced into the
Late Miocene, when obligate bipedalism probably became a regular component of one or
more hominoid lineages.
The development of obligate terrestrial bipedalism established a new adaptive zone
for some anthropoid primates, which then radiated and deployed to establish terrestrial
niches in forests, closed woodlands, open woodlands and yet more open areas over a span
of at least 4.5 million years. Detailed documentation of our first bipedal steps and later
developments of prolonged orthograde bipedal stance, striding and running in our lineage
has been and perhaps always will be elusive because commonly early postcranial specimens
are not assuredly associated with telling craniodental remains, which are the stock-intrade of the paleoanthropological systematist. The postcranial fossil gap is particularly
frustrating to cladistically inclined architects of phylogenic models, who because of the
dearth of specimens enter fewer postcranial than craniodental traits into their analyses.
Wood and Collard’s (1999) emphasis on postcranial morphology in hominoid
systematics is laudable; in the long run it probably will be more productive than heavy
reliance on either molecular genetics or cladistic analyses of the craniodental traits that
happen to have been preserved without a full set of features from the rest of the organisms
Table 1. A partial taxonomy of the Hominoidea
Hominoidea
Hominidae
Paranthropinae
Paranthropus aethiopicus
Paranthropus boisei
Paranthropus robustus
Australopithecinae
Australopithecus afarensis
Australopithecus africanus
Australopithecus anamensis
Australopithecus bahrelghazali
Australopithecus garhi
Australopithecus habilis
Homininae
Homo sapiens
Homo neanderthalensis
Homo erectus
Homo ergaster
Homo antecessor
Homo heidelbergensis
Homo rudolfensis
Subfamily incertae sedis
Ardipithecus ramidus
Ardipithecus kadabba
Kenyanthropus platyops
Orrorin tugensis
Sahelanthropus tchadensis
Panidae
Paninae
Pan paniscus
Pan troglodytes
Gorillinae
Gorilla beringei
Gorilla gorilla
Pongidae
Pongo abelii
Pongo pygmaeus
Hylobatidae
Bunopithecus hoolock
Hylobates agilis
Hylobates klossii
Hylobates lar
Hylobates moloch
Hylobates muelleri
Hylobates pileatus
Nomascus concolor
Nomascus gabriellae
Nomascus leucogenys
Nomascus nasutus
Symphalangus syndactylus
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that are being compared.
Within the Hominidae sensu stricto, several subfamilies may be identified partly
according to the extent to which they exhibit anatomical features that suggest full
commitment to terrestrial niches via bipedal adaptive complexes versus continued reliance
on arboreal climbing. Complexes of craniodental features may further warrant grouping
some species into subfamilies. I suggest that there are at least 3 subfamilies in the
Hominidae: Paranthropinae, Australopithecinae, and Homininae, with Ardipithecus ramidus,
A. kadabba, Kenyanthropus platyops, Orrorin tugenensis, and Sahelanthropus tchadensis
subfamilially incertae sedis (Table 1).
Species of Australopithecus and Paranthropus, which, though obligately bipedal on
the ground, also exhibit anatomical features suggesting notable reliance on arboreal
climbing, are subfamilially discrete from species of Homo, which are fully committed
morphologically and neurophysiologically to a terrestrial adaptive zone. Were Ardipithecus
ramidus, A. kadabba, Kenyanthropus, Orrorin, and Sahelanthropus to lack features of the
lower limb and spine that are related to terrestrial bipedalism, they might be removed to
the Panidae or another family of the Hominoidea.
4. PARANTHROPINAE
The cladistic analyses of craniodental traits by Strait et al. (1997) indicate that the three
species of Paranthropus—Paranthropus aethiopicus, Paranthropus boisei, and
Paranthropus robustus—compose a monophyletic group. Sparse, mostly fragmentary
postcranial morphology is known only for Paranthropus robustus and Paranthropus boisei
(McHenry, 1994; Grausz et al., 1988). All studies indicate that in many features of the
upper and lower limbs Paranthropus was more like Australopithecus than like Homo sapiens
(Grausz et al., 1988; McHenry, 1994). Accordingly, even though they were probably
terrestrially bipedal, they appear to have retained features that are commonly associated
with arboreal activities and bipedalism somehow different from that of Homo: relatively
long upper limbs, small femoral heads, anteroposterially flattened femoral necks, flared
iliac blades, long ischial bodies, and curved manual phalanges (Robinson, 1972; McHenry,
1994).
Shipman and Harris (1988) found that in eastern Africa, Paranthropus boisei and
Paranthropus aethiopicus are strongly and persistently associated with closed habitats,
though at Konso, Ethiopia, Paranthropus boisei lived in a grassland habitat (Suwa et al.,
1997). The South African cave sites of Paranthropus robustus are associated with open/
arid habitats, which may reflect taphonomic bias rather than their actual foraging preference
since rivers and sizeable waterholes in the grasslands would be bordered by trees and
thickets (Vrba, 1988; Shipman and Harris, 1988).
Dental morphology and wear patterns indicate that Paranthropus robustus ate hard
food items, perhaps like those in the Transvaal today (Kay and Grine, 1988; Peters, 1993),
and that East Turkanan Paranthropus boisei chewed whole pods and fruits with hard
pericarps and tough seeds, but probably did not masticate quantities of grass seed, leaves
or bone (Walker, 1981). It will be interesting to learn the dietary habits that are indicated
by microwear on the teeth of Konso Paranthropus boisei.
ARE HUMAN BEINGS APES, OR ARE APES PEOPLE TOO?
253
5. AUSTRALOPITHECINAE
Of the six species of Australopithecus (Table 1), only Australopithecus africanus is securely
placed in the Australopithecinae. Cladistic analyses of craniodental traits have not
comprehensively included the gnathodental specimens of Australopithecus bahrelghazali
(Brunet et al., 1995, 1996) and specimens of Australopithecus garhi (Asfaw et al., 1999),
Australopithecus anamensis (Leakey et al., 1995), Ardipithecus kadabba (Haile-Selassie
et al., 2004) and Ardipithecus ramidus (White et al., 1994, 1995) or of the Turkwel hominids
(Ward et al., 1999). Further, Pickford and Ishida (1998) were inclined to sink
Australopithecus anamensis into Praeanthropus afarensis, and Wood and Collard (1999)
have referred Homo habilis sensu stricto (Lieberman et al., 1996) to Australopithecus, as
Australopithecus habilis, based largely on their postcranial anatomy, which suggests arboreal
climbing.
Wood and Collard (1999) also referred Homo rudolfensis to Australopithecus, as
Australopithecus rudolfensis. The assignment of the hypodigm to Australopithecus
rudolfensis versus Homo rudolfensis is problematic in a scheme that has among its chief
criterion for generic status postcranial features related to fully hominine bipedalism versus
a compromise between arboreal climbing and terrestrial bipedality.
Because very hominine postcranial remains occur contemporaneously with the type
specimen of Homo rudolfensis at East Turkana, Kenya, it probably is premature to transfer
the species to Australopithecus. Indeed in 1992, Wood included a hominine talus (KNMER 813) and two femora (KNM-ER 1472 and KNM-ER 1481A) in Homo rudolfensis.
Tardieu (1999) noted that a dual attachment of the lateral meniscus on the tibial plateau
indicates that KNM-ER 1481B and KNM-ER 1476B are hominine, and unlike
australopithecines, which apparently had a single attachment of the lateral meniscus in the
knee. The hominine partial hip bone (KNM-ER 3228; Rose 1984) from the Lower Member
of the Koobi Fora Formation is also reasonably placed in the hypodigm (McHenry, 1994).
A more comprehensive cladistic analysis than that conducted by Strait et al. (1997),
particularly one that includes a rich complement of postcranial traits, might bring
Australopithecus afarensis and perhaps Ardipithecus spp. into the Australopithecinae.
6. HOMININAE
Pedal anatomy is basically unknown for Homo ergaster, as represented postcranially by
KNM-WT 15000, but there is no reason to doubt that they were exclusively committed to
terrestrial bipedalism, like that of modern human beings (Walker and Leakey, 1993). Indeed,
no hominid younger than 1.5 Ma exhibits the climbing features that characterize
Australopithcus and Paranthropus. Therefore, we may assume that, like Homo sapiens
and Homo neanderthalensis (Trinkaus et al., 1998), for which there is abundant data, Homo
erectus (Rightmire, 1990), Homo heidelbergensis (Roberts et al., 1994), and Homo
antecessor were essentially modern bipeds.
Wood and Collard (1999) reasonably challenged the view that endocranial volumes ≥
600 cm3, endocranial markers purportedly indicating language capacity, hands with
humanoid precision grip, and the ability to make stone tools are sufficient criteria for
membership in Homo. Instead, they proposed that species of Homo should evidence
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commonality in their adaptive strategies to maintain homeostasis, to acquire food, and to
produce offspring, which would set them apart from those of Australopithecus,
Paranthropus, and Ardipithecus. Because Homo habilis and Homo rudolfensis had jaws
that suggest heavy chewing and dental development more like those of Australopithecus
than that of Homo sapiens, Wood and Collard (1999) moved them to Australopithecus.
This accords well with postcranial inferences in the case of Australopithecus habilis, but
as mentioned above, it probably is discordant with postcranial specimens that may belong
to Homo rudolfensis.
7. CULTURED APES AND THE EVOLUTION OF CULTURE
A collateral consequence of removing the oft-cited craniodental and handy features as
chief criteria for Homo is that we are freer to postulate the development and occurrence of
language and stone tool-using among any or all Plio-Pleistocene hominid genera and species.
Moreover, it is easier to imagine that extant apes, particularly chimpanzees, excel some
Plio-Pleistocene hominid species in tool behaviors and perhaps in intraspecific
communication.
There never has been and probably never will be sufficient evidence to ascribe or to
deny speech or a gestural form of language for any fossil hominid species from relatively
intact, let alone crushed skulls and natural endocasts, since features related to language are
not indelibly impressed on the surface of the human brain (Tuttle, 2001; Deacon, 1997).
Nor can one discount language capacity in fossil hominids based on bones bounding the
vocal tract (Tuttle, 2001).
Apes and many monkeys are dexterous enough to make and to use the simple stone
artifacts that begin to appear in the archaeological record at 2.5 Ma; therefore, the hand
bones of late Pliocene-Early Pleistocene Hominidae are not secure guides to which species
were tool whizzes (Tuttle, 1967). Indeed, it is possible that tool behavior, largely employing
vegetal and other natural objects, was part and parcel of hominid foraging and defensive
behaviors for hundreds of millennia before some species began to modify stone and bone
for special tasks.
At what point in the development of hominid tool behavior and intraspecific
communication can we assume that a given species has culture? This question could be
informed by controlled comparisons of cognitive and neural substrates of tool behavior
and intraspecific communication in living apes versus people.
A group of 9 veteran field and laboratory researchers (Whiten et al., 1999) concluded
that chimpanzees are cultural beings, and Nature declared that cultural primatology has
come of age (de Waal, 1999). De Waal (1999:635) remarked that “the record is so
impressive that it will be hard to keep these apes out of the cultural domain without once
again moving the goalposts.”
What is the ultimate goal here? For instance, should chimpanzees be considered people
because they are cultural beings? If so, will an expanded critical multiculturalism (Turner,
1993) free incarcerated individuals and protect remaining populations of Pan troglodytes
from further depredations by Homo sapiens?
To the latter question, regrettably I think not, given the slow progress of human rights
and mutual respect in many parts of the world, including privileged Western societies.
ARE HUMAN BEINGS APES, OR ARE APES PEOPLE TOO?
255
Indeed, such a declaration might make more apes pawns of politicos and targets of resentful
people, as some people and other animals are today.
In the first instance, we must define culture and decide whether that which we would
designate as culture is homologous in apes and humans, at least insofar as it is predisposed
by common genetic substrates. Advocates of chimpanzee culture emphasize social or
observational learning and imitation of behaviors that become demic traditions in particular
groups (Whiten et al., 1999). The cited examples of chimpanzee culture do not include
explication of their meanings to the chimpanzees themselves. Specifically, there is no
reference to symbolic mediation or a comparable mechanism that would underpin shared
values, ideas and beliefs about their tool behavior, grooming postures, noise-making and
athletic displays. To many anthropologists, this is the sine qua non of culture (Geertz,
1973; White and Dillingham, 1973; Keesing, 1974; Durham, 1991; Kuper, 1999; Harris,
1999), whose development should be the focus of research by evolutionary primatologists
and anthropologists if we are to have a cultural primatology.
Although captive apes may participate with humans in artifactual cultures at the level
of young children (Savage-Rumbaugh et al., 1998; Fouts and Mills, 1997; Miles, 1999;
Patterson and Cohn, 1994), they have not been found naturalistically to possess culture,
i.e. symbolically mediated behavior, ideas, beliefs and values. The demic traditions
described by Whiten et al. (1999) would constitute cultures if, and only if, their focal
chimpanzees were proved to be cultural, i.e. symboling, beings.
The challenge before us is to crack the communicative codes of apes in natural habitats
and noninvasively to explore the nervous systems, vocal tracts, and other anatomical
structures related to vocalization and gesture to discern whether apes naturalistically symbol
(White and Dillingham, 1973) even though they lack humanoid speech.
Our primary goal should be to understand apes and other organisms in all their
wonderful specialness. Apes comprise a bonus for evolutionary anthropologists in providing
a rich basis for fleshing out and acting out our bony Miocene-Pleistocene predecessors,
albeit with the caveat that their behavioral repertoires are undoubtedly different in some
aspects from those of apish species in our lineage. Were they to be found to symbol
naturalistically, they would be symboling apes, with much more to teach us about how we
became people.
8. ACKNOWLEDGEMENTS
This paper is dedicated to Dr. Shiro Kondo, a visionary scientist, whose mentoring of
younger scientists contributed enormously to the development of evolutionary anthropology
in Japan with strong links to colleagues internationally. I thank the organizers of the Center
for Excellence International Symposium on Evolution of the Apes and the Origin of Human
Beings, who were gracious hosts and highly informative colleagues. Special gratitude is
also due to Drs. Hidemi Ishida, Yuzuru Hamada, and Yutaka Kunimatsu and their students
in evolutionary anthropology for ensuring that our evenings were enriched with fine dining
and lively conversation.
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