Journal of Human Evolution 50 (2006) 78e95
Dental microwear and diets of African early Homo
Peter S. Ungar a,*, Frederick E. Grine b, Mark F. Teaford c, Sireen El Zaatari d
a
Department of Anthropology, University of Arkansas, Fayetteville, AR 72701, USA
Departments of Anthropology and Anatomical Sciences, Stony Brook University, Stony Brook, NY 11794, USA
c
Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, 1830 E. Monument St., Baltimore, MD 21205, USA
d
Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
b
Received 11 March 2005; accepted 22 August 2005
Abstract
Conventional wisdom ties the origin and early evolution of the genus Homo to environmental changes that occurred near the end of the Pliocene. The basic idea is that changing habitats led to new diets emphasizing savanna resources, such as herd mammals or underground storage
organs. Fossil teeth provide the most direct evidence available for evaluating this theory. In this paper, we present a comprehensive study
of dental microwear in Plio-Pleistocene Homo from Africa. We examined all available cheek teeth from Ethiopia, Kenya, Tanzania,
Malawi, and South Africa and found 18 that preserved antemortem microwear. Microwear features were measured and compared for these specimens and a baseline series of five extant primate species (Cebus apella, Gorilla gorilla, Lophocebus albigena, Pan troglodytes, and Papio ursinus)
and two protohistoric human foraging groups (Aleut and Arikara) with documented differences in diet and subsistence strategies. Results confirmed that dental microwear reflects diet, such that hard-object specialists tend to have more large microwear pits, whereas tough food eaters
usually have more striations and smaller microwear features. Early Homo specimens clustered with baseline groups that do not prefer fracture
resistant foods. Still, Homo erectus and individuals from Swartkrans Member 1 had more small pits than Homo habilis and specimens from
Sterkfontein Member 5C. These results suggest that none of the early Homo groups specialized on very hard or tough foods, but that H. erectus
and Swartkrans Member 1 individuals ate, at least occasionally, more brittle or tough items than other fossil hominins studied.
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Hominin; Feeding adaptations; Homo habilis; Homo rudolfensis; Homo erectus
Introduction
Diet underlies many of the behavioral and ecological differences that separate primate species (and foraging peoples)
from one another, and should therefore be a key to understanding the paleobiology and ecology of early hominins.
It follows, then, that changes in feeding adaptations should
have also played an important role in the origin and early
evolution of the genus Homo. While there is considerable
interest in the evolution of human diet, the dental evidence
for feeding behaviors among the earliest representatives of
* Corresponding author. Tel.: C1 479 575 6361; fax: C1 479 575 6595.
E-mail addresses: [email protected] (P.S. Ungar), [email protected].
edu (F.E. Grine), [email protected] (M.F. Teaford), [email protected]
(S. El Zaatari).
0047-2484/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jhevol.2005.08.007
our genus has received little attention compared with
analyses of their australopith predecessors. In this paper,
we present the first comprehensive molar microwear
analysis of Homo specimens from the Plio-Pleistocene of
Africa.
Models for the diets of early Homo
Researchers have created elaborate scenarios for the origin
and early evolution of our genus. Most of these depend on the
apparent contemporaneity of early Homo species, Oldowan
technology, and the spread of C4 grasslands across eastern
and southern Africa. According to these models, environmental change provided the motive, and technology offered the opportunity for the origin and adaptive radiation of our genus.
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
The three commonly recognized species of African early
Homo have overlapping geochronological ranges, perhaps indicating coexistence over two hundred millennia or more.
Most Homo habilis specimens come from Olduvai Gorge
and Koobi Fora, and date to between ca. 1.87 Ma and
1.65 Ma, although A.L. 666-1 from Hadar possibly extends
the range of this species back to 2.33 Ma (Kimbel et al.,
1996). Specimens attributed to H. habilis at Sterkfontein fall
within this time frame (Tobias, 1991). Homo rudolfensis has
a similar temporal range, with most fossils dating between
1.90 Ma and 1.85 Ma at Koobi Fora. Other specimens from
Koobi Fora, the Omo, Chemeron, and Malawi might extend
this range to between 2.4 Ma and 1.55 Ma (Wood, 1991a;
Bromage et al., 1995; Suwa et al., 1996; Sherwood et al.,
2002). East African Homo erectus had an even greater temporal span, from 1.89 Ma (or perhaps even 1.95 Ma) at Koobi
Fora to less than 660 ka at Baringo (Susman et al., 1983;
Wood and Vannoten, 1986; Feibel et al., 1989). Homo erectus
specimens from Swartkrans also fall within this temporal
range (Vrba, 1985; Rightmire, 1990b; Tobias, 1991; Wood,
1991a; McKee et al., 1995).
Most researchers relate the first appearances of these species during the late Pliocene to major episodes of global cooling and drying (Vrba et al., 1995). C4 grasslands evidently
spread across eastern Africa after about 2.5 Ma, concomitant
with periodic fluctuations in climate (Cerling, 1992). This
change corresponds roughly to the postulated times of the
emergence of H. habilis and H. rudolfensis. Climate may
have played a role in the origin of H. erectus, too, as this species appeared during a period of significant faunal turnover
(Behrensmeyer et al., 1997). Although researchers debate the
tempo of this turnover (Potts, 1998), most agree that changes
to cooler, more variable climates had a substantial effect on
mammalian diversity, including early Homo.
The earliest archaeological remains date to about 2.5 Ma,
and include both stone tools and cut-marked faunal remains
from Ethiopia (de Heinzelin et al., 1999; Semaw et al.,
2003). This material demonstrates that Pliocene hominins
were making and using stone tools to process animal remains,
almost certainly for consumption. While other hominins were
present at the time (Walker et al., 1986; Asfaw et al., 1999),
most would agree that one or more species of early Homo
most likely made and used Oldowan technology. The appearance of stone tools suggests an expanded toolkit beyond the
perishable items used by living great apes for the procurement
or preparation of food (Panger et al., 2002). It is also noteworthy that the earliest large concentrations of stone tools and
modified bones at sites such as DK and FLK 22 at Olduvai
Gorge and FxJj 1 at Koobi Fora are approximately coincident
with the earliest known H. erectus (Blumenschine and Masao,
1991).
In sum, there is near synchrony of three events in East
Africa approximately 2.5 Ma: 1) the emergence of Homo
habilis and H. rudolfensis; 2) the beginning of the spread of
grasslands and increasing climatic variation; and 3) the appearance of the earliest modified stone tools and cut-marked
bones. Furthermore, H. erectus appears at about the same
79
time as large archaeological concentrations and significant faunal turnover. These concurrent events may or may not be related, but they have served as the basis for scenarios used to
explain the origin and early radiation of our genus. Changing
environments and an expanded tool kit have been linked with
a changing resource base and changing dietary adaptations.
These scenarios come in ‘‘meat-eating’’ and ‘‘plant-eating’’
varieties.
Meat-eating scenarios
Darwin (1871) considered hunting and meat consumption
to have played important roles in human evolution, and
many have developed this notion since. The idea is that, as
grasslands began to spread and forest resources became
scarce, hominins relied more and more on savanna adapted ungulates as a food source. This change in ecology started a feedback loop wherein improved hunting abilities followed an
expanded toolkit, increased sociality, and larger brains, which
were made possible by increased protein consumption (Washburn, 1963; Lee and Devore, 1968; Isaac, 1971; Dart and Wolberg, 1971; Daegling and Hylander, 2000; Stanford and Bunn,
2004). These scenarios have become increasingly sophisticated with improved understanding of nutrition and digestive
physiology. Some recent models consider possible relationships between meat consumption and brain size in light of
tissue energy requirements (Milton, 1987; Leonard and
Robertson, 1994; Aiello and Wheeler, 1995). Others stress
the role of animal fat as a possible source of long-chain polyunsaturated fatty acids to help form brain tissue (Speth, 1989;
Eaton et al., 2002).
Plant-eating scenarios
Other researchers have argued that hominins began to focus
on xeric plants rather than animals as the savanna spread
across eastern and southern Africa during the Plio-Pleistocene
(Linton, 1971; Wolpoff, 1973; Coursey, 1973). Indeed, most
documented human foragers eat more plant foods than meat
(Zihlman and Tanner, 1978). Recent models that emphasize
xeric plant consumption by early hominins have focused on
underground storage organs, or USOs. The two most common
scenarios, the ‘‘Grandmother hypothesis’’ (O’Connell et al.,
1999) and the ‘‘Cooking hypothesis’’ (Wrangham et al.,
1999), share much in common. Both include a transition
from ‘‘apelike’’ to ‘‘humanlike’’ subsistence in H. erectus, as
evidenced by larger female body mass and a reduction in tooth
size.
These models are often sophisticated and elegant, but they
do not tell us what early Homo ate. We prefer to view them as
hypotheses, some of which may be tested with data derived
from the hominin fossils themselves. While researchers have
considered the dietary implications of tooth size, shape, and
mineralized tissue chemistry of early Homo (for a review,
see Ungar et al., in press), very limited work has been published for these species on one of the most effective and
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P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
broadly applied methods for inferring diets of past peoples and
fossil speciesddental microwear.
Dental microwear of early Homo
Dental microwear research has now been carried out for
more than half a century, and numerous studies have documented relationships between the densities, sizes, and shapes
of microscopic wear features in teeth and the fracture properties of foods eaten by living primates and other mammals (for
reviews, see Teaford, 1991; Rose and Ungar, 1998; Ungar,
2002b). Primates that eat mostly hard, brittle nuts and seeds,
for example, have more microwear pitting, whereas those
that eat tough leaves often have relatively more microwear
striations. Species that consume soft fruits tend to be intermediate in their ratios of pits to scratches (Teaford and Walker,
1984; Teaford, 1988a). Studies of wild populations of primates
have shown that microwear can, in fact, reflect rather subtle
differences in diet between populations (Teaford, 1985;
Teaford and Robinson, 1989; Teaford and Glander, 1991).
There have been few studies of the dental microwear of early
Homo, but the limited work that has been done hints at some
interesting possibilities. Puech and colleagues (Puech et al.,
1983a; Puech, 1984) noted, for example, evidence of enamel
and dentine erosion on some molar teeth of H. habilis from Olduvai Gorge. This implied to them the consumption of unripe,
acidic fruits by these hominins. In another study, Waddle
(1988) found high incidences of small microwear pits in the
occlusal surfaces of some early Homo molars from Swartkrans
(Members 1 and 2). While she considered this study preliminary, its results might be consistent with Walker and Shipman’s
(1997) observations of ‘‘extreme gouging and battering’’ in
eastern African H. erectus cheek teeth. Finally, Martı́nez et al.
(2004) examined buccal surface microwear in H. habilis specimens from eastern Africa. Their study focused not on diet reconstruction per se, but rather on the relationship (or lack thereof)
between microwear density and inferred age of death. These
studies make it clear that much work remains to be done on
the dietary implications of dental microwear in early Homo.
we deemed them too fragile to mold. All other specimens
were replicated following standard procedures (see below).
Casts of cheek teeth were produced for 83 specimens. These
fossils were recovered from 1) Sterkfontein, Swartkrans, and
Drimolen in South Africa; 2) Olduvai Gorge in Tanzania; 3)
Koobi Fora, West Turkana, Baringo, and Lainyamok in Kenya;
and 4) the Omo and Hadar in Ethiopia. Casts of the UR 501
molar teeth from Uraha, Malawi were also prepared (molds
courtesy of Tim Bromage).
Tooth replicas were first examined by binocular light microscopy at 50! and, if necessary, at 500! by scanning electron microscopy to determine suitability for microwear
analysis. The vast majority of specimens were deemed unsuitable because of taphonomic damage (e.g., etching, erosion)
that obscured or obliterated antemortem microwear. This circumstance was most often the case for surface finds and specimens that had been subjected to fluvial transport. Specific
criteria used to evaluate occlusal surfaces are presented in detail elsewhere (Teaford, 1988b; King et al., 1999). A few other
specimens had to be excluded because they are unworn. Ultimately, we could include with confidence only 18 specimens
(n Z 5 for Homo erectus; n Z 6 for Homo habilis; n Z 3 for
early Homo from Sterkfontein Member 5C, and n Z 4 for
early Homo from Swartkrans Member 1) in this microwear
analysis. Those specimens that did not preserve antemortem
microwear can be identified by comparing the list of all specimens examined (Appendix I) with those used in this study
(Table 1). The usable fraction of the total sample (ca. 23%)
is similar to that found for Plio-Pleistocene monkeys from
some of these same sites (Leakey et al., 2003; El Zaatari
et al., 2005).
Table 1
Tooth type, stratigraphic derivation, and taxonomic attribution of Homo specimens for which microwear data could be obtained
Specimen
Tooth
Formation
Member
OH 4
OH 7
OH 15
OH 16
OH 41
Stw 19b
LM3
LM2
RM3
LM2
LM1
RM2
Olduvai Gorge
Olduvai Gorge
Olduvai Gorge
Olduvai Gorge
Olduvai Gorge
Sterkfontein
Bed I
Bed I
Bed II
Lemuta Mb.
Bed II
Dump D-3*
Homo
Homo
Homo
Homo
Homo
Homo
habilis
habilis
habilis
habilis
habilis
habilis
This study presents dental microwear data for all available
early Homo molar specimens from eastern and southern
Africa. These data are compared with those for a baseline series of human groups with documented subsistence practices
and nonhuman primate species with known differences in diet.
KNM-ER 807
KNM-ER 820
KNM-WT 15000
OH 60
SK 15
RM1 Koobi Fora Fm.
RM1 Koobi Fora Fm.
LM1 Nachukui Fm.
RM3 Olduvai Gorge
LM1
Swartkrans
KBS Mb.
Okote Mb.
Natoo Mb.
Bed I
HR, Mb. 2
Homo
Homo
Homo
Homo
Homo
erectus
erectus
erectus
erectus
erectus
The fossil sample
SE 1508
SE 1579
Stw 80
LM1
LM1
LP4
Sterkfontein
Sterkfontein
Sterkfontein
SK
SK
SK
SK
LM1
RM2
LM3
LM3
Swartkrans
Swartkrans
Swartkrans
Swartkrans
Materials and methods
We examined all available molar teeth of Homo specimens
from the Plio-Pleistocene of Africa at the National Museum of
Ethiopia, the National Museums of Kenya, the National Museum of Tanzania, the Transvaal Museum, and the University
of the Witwatersrand. A few specimens were excluded from
this study following initial inspection because of obvious
postmortem damage to entire occlusal surfaces or because
27
45
847
2635
Homo sp. indet. A
Homo sp. indet. A
Homo sp. indet. A
Mb. 5C
Mb. 5C
Mb. 5C
HR,
HR,
HR,
HR,
Mb.
Mb.
Mb.
Mb.
Taxonomic
attribution
1
1
1
1
Homo
Homo
Homo
Homo
sp.
sp.
sp.
sp.
indet.
indet.
indet.
indet.
B
B
B
B
* Stw 19b was recovered from Dump D-3, while associated specimens Stw
33 (LP4) and Stw 34 (LM2) are recorded as having been recovered from Dump
D-18, which Kuman and Clarke (2000) believe must be an error. Dump D-3
breccia is consistent with its derivation from Member 5A.
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
Specimen attributions
There is currently no consensus among paleoanthropologists
concerning either the number of Plioceneeearly Pleistocene
species attributable to Homo or the hypodigms of these taxa
(Stringer, 1986; Lieberman et al., 1988; Chamberlain, 1989;
Groves, 1989; Rightmire, 1990a; Miller, 1991; Wood,
1991a,b, 1992; Rightmire, 1993; Grine et al., 1993, 1996;
Blumenschine et al., 2003). While a comprehensive review of
the arguments is beyond the scope of this paper, the taxonomic
attribution of the specimens needs to be discussed because it can
have marked effects on the interpretation of microwear data.
We recognize at least three species of early Homo in the
Plio-Pleistocene deposits of eastern and southern Africa, including H. habilis, H. rudolfensis, and H. erectus (ZHomo
ergaster). We concur with Wood (1991a, 1992, 1993) and
others in distinguishing two species among the craniodental
specimens traditionally regarded (Howell, 1978; Tobias,
1991) as Homo habilis,1 namely H. habilis sensu stricto and
H. rudolfensis. On the other hand, we do not distinguish
H. ergaster as a separate species from H. erectus; rather, we
agree with those that observe continuous variation among these
fossils, and regard them as constituting a single species lineage
(e.g., Rightmire, 1990b; Bräuer and Mbua, 1992; Bräuer, 1994).
While some have suggested that there is more than one species in the traditional H. habilis hypodigm from Olduvai Gorge
(Leakey, 1976; Rightmire, 1993; Blumenschine et al., 2003),
we accept the attributions of Wood (1991a, 1992, 1993) and
Tobias (1991), who have undertaken the most exhaustive studies of these fossils to date. Thus, OH 4, OH 7, OH 15, OH 16,
and OH 41 are considered to represent H. habilis for the purposes of the analyses presented here. None of the specimens
from the Shungura Formation, Koobi Fora Formation, and
Chiwondo Beds that have been attributed or likened to H. rudolfensis by Wood (1991a, 1992, 1993), Bromage et al. (1995),
and Suwa et al. (1996) preserve molars that are useful for the
study of microwear. The usable dental sample for H. erectus
molars from eastern Africa includes two specimens from
Koobi Fora (KNM-ER 807, KNM-ER 820) and the Nariokotome boy (KNM-WT 15000). One additional specimen from
Olduvai Gorge, OH 60, has been attributed to H. erectus on
the basis of very small size (Ungar et al., 2001).
Most workers that have studied the hominin remains from
Sterkfontein have attributed or likened the Stw 53 cranium
from Member 5A (Partridge, 2000) to H. habilis (Howell,
1978; Tobias, 1991). The Stw 19b molar was recovered
from a breccia dump, the composition of which suggests
that it is likely to have come from Member 5A, which is referred to by Kuman and Clarke (2000) as the ‘‘Stw 53 infill.’’
1
Homo habilis and H. rudolfensis may not display ‘‘adaptive coherence’’
with Homo sapiens (Wood and Collard, 1999). However, there is strong evidence that they share a closer evolutionary relationship with later species of
Homo than with any currently recognized species of Australopithecus (Strait
and Grine, 2001). As such, the generic assignment of H. habilis and H. rudolfensis is largely a matter of personal preference and does not affect the question of whether or not they are distinct species.
81
We follow the attribution of specimens from this particular
sedimentary unit to H. habilis (Howell, 1978; Tobias, 1991;
Kimbel et al., 1997).
The taxonomy of other Homo specimens from Sterkfontein
is less certain. Tobias (1965) likened specimens from Robinson’s excavations of the ‘‘Extension Site’’ [Member 5C of
Partridge (2000)] to H. habilis. Kuman and Clarke (2000),
on the other hand, suggested that the Stw 80 mandible, excavated from this deposit by Hughes, is similar to the Swartkrans
Member 1 jaw, SK 15, which has been attributed to H. erectus
(or H. ergaster) by most workers (Howell, 1978; Rightmire,
1990a; Kuman and Clarke, 2000). In addition to Stw 80,
a number of isolated teeth have been recovered from Sterkfontein Member 5C (Stw 82, SE 1508, and SE 1579). Because
there is a lack of consensus or empirical evidence pertaining
to the specific attribution of these Member 5C specimens,
we treat them as a separate group.
The taxonomy of Swartkrans specimens that belong to the
genus Homo has been reviewed recently by Grine (2005).
Most workers accept that the Member 2 fossils, including
SK 15, are attributable to H. erectus (Robinson, 1961; Howell,
1978; Rightmire, 1990a; Tobias, 1991; Wood, 1991a). We follow these researchers, and include SK 15 in that species.
On the other hand, there is a notable lack of consensus regarding the specific attribution(s) of the Swartkrans Member 1
specimens. They have recently been referred to H. erectus,
H. habilis, or possibly a novel species that is not currently
recognized in the Plio-Pleistocene deposits of eastern Africa
(Howell, 1978; Walker, 1981; Clarke, 1985; Bilsborough and
Wood, 1988; Tobias, 1991; Grine et al., 1993, 1996; Kimbel
et al., 1997; Grine, 2001). Because of this debate, we treat
the Swartkrans Member 1 specimens (SK 27, SK 45, SK
847, SK 2635) as a separate group. The descriptive statistics
calculated for microwear variables for each of these specimens
are presented in Appendix II to allow others to group specimens and perform analyses according to their own preferred
taxonomies.
The baseline sample
The baseline sample used in this analysis was divided into
four groups: extant African apes, ‘‘hard-object’’ feeding monkeys, USO-eating chacma baboons, and archaeological samples of protohistoric peoples (see Appendix II for a list of
specimens).
All of the extant primate species studied here have been analyzed for dental microwear patterns previously (Teaford and
Walker, 1984; Teaford, 1988a; Daegling and Grine, 1999).
These taxa were studied by different observers using different
analytical techniques. Direct comparison of published results
with one another, or with results for fossils presented here
would, however, be problematic. Overall, interobserver error
rates are about 9% using a given technique, and results obtained through different quantification protocols vary by about
17% (Grine et al., 2002). This should serve as a cautionary tale
for those who assemble and compare microwear data from different research projects, especially those that employ different
82
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
techniques of microwear analysis. In order to ensure the legitimacy of our baseline series for interpreting the early Homo
results, we analyzed both the fossils and all extant taxa (including those for which data are already available in the literature) using the same observers and the same analytical
protocol (see below).
The African apes were included in the comparison because
they have been suggested to be reasonable models for early
hominin behavior, especially given phyletic affinities (see
Rodman, 2002, and references therein). We analyzed the subspecies Pan troglodytes troglodytes and Gorilla gorilla beringei because of their contrasting diets (see below). Cebus apella
and Lophocebus albigena were included because of suggestions that early hominins may have evolved as hard-object
feeders (Kay, 1981). Papio ursinus was included because of
recent emphasis on USOs as an important or keystone resource
for early Homo (see above). Finally, two human groups were
included because of plausible similarities in subsistence practices between recent foraging peoples and early Homo. The
Arikara and Aleut were selected because their diets are well
documented and differ in the degree of animal tissue consumption. This difference is important, given hypotheses concerning the role of meat in the diets of early Homo.
The diets of these peoples and nonhuman primates are recorded with varying degrees of detail in the literature. Furthermore, interpretations of microwear results for museum
specimens based on naturalistic studies of other individuals
in the wild should not be pushed too far. Primate diets can
be affected by idiocyncratic food preferences and differences
in microhabitat, study site, observation technique, season,
and even year of observation (Olupot, 1998; Doran et al.,
2002; Chapman et al., 2002). Because we do not have specific
feeding information for the individuals considered in this analysis, summaries presented here should only be taken as rough
guides when interpreting microwear.
Gorilla gorilla beringei is the most folivorous of the gorilla
subspecies. Specimens included in this study come from
a very well-documented sample housed at the U.S. National
Museum of Natural History. These individuals were exhumed
and collected in the Virunga Mountains in 1979 and identified
by Dian Fossey and Jay Matternes. Many were studied in the
wild, with individual names recorded for specimens (Fossey,
1983). Virunga mountain gorilla diets are dominated by leaves
and stems, which often make up more than 90% of foods eaten
(Fossey and Harcourt, 1977; Vedder, 1984; Watts, 1984,
1990). Mountain gorillas living at lower elevations, such as
at Bwindi, take more fruits as availability permits (Robbins
and McNeilage, 2003; Stanford and Nkurunungi, 2003), but
even these populations eat mostly leaves.
Pan troglodytes troglodytes, in contrast, consumes mostly
fruits. The sample studied here comes from the HammonTodd Osteological Collection at the Cleveland Museum of
Natural History. Most specimens were collected near Abong
Mbang in eastern Cameroon. Not a great deal is known about
this subspecies in Cameroon, but the central African chimpanzee has been the subject of long term study in the Lopé Reserve, Gabon, and the Ndoki Forest, Congo. Diets reported
for chimpanzees at Lopé and Ndoki are very similar, and are
dominated by fruits (between 70% and 80% of the diet; Tutin
and Fernandez, 1985; Kuroda, 1992; Tutin et al., 1997). Other
foods eaten include leaves (12%e13%), seeds (5%e10%),
and occasionally pith and flowers.
Cebus apella and Lophocebus albigena are commonly included in studies of primate functional morphology (Kay,
1981; Dumont, 1995) and dental microwear (Teaford and
Walker, 1984; Teaford, 1988a) as ‘‘hard-object’’ specialists,
with adaptations for crushing brittle items, especially nuts.
In fact, these primates eat a lot of things, although they do include more hard, brittle foods in their diets than do other primates living in the forests with them. Capuchin and mangabey
specimens examined for this study are all housed at the U.S.
National Museum of Natural History.
The C. apella specimens analyzed in this study consist of
wild-shot individuals from Amazonas in Venezuela and from
Demerara-Mahaica and the headwaters of the Essiquibo River
in Guyana. There is no information on season of capture.
Eisenberg (1989) summarized their diets as comprising 66%
fruit flesh, 25% seeds, 7% pith, and occasional insects and
other prey. While Brown and Zunino (1990) reported that
some brown capuchins in Argentina consume more bromeliad
leaves and insects, specimens included in the microwear study
were restricted to the tropical part of their distribution, where
C. apella is noted to consume hard, brittle foods more often
than do other sympatric primate species (Terborgh, 1983;
Janson and Boinski, 1992).
Lophocebus albigena specimens examined for this study
were wild-shot in Congo and Uganda. All specimens examined were collected in the early and middle 20th century during the months of November and December. Grey-cheeked
mangabeys are predominately frugivorous, with fruits (including seeds) constituting about 60% of the annual diet at sites
ranging from the Dja Reserve in Cameroon to Lopé in Gabon
and Kibale in Uganda (Ham, 1994; Olupot, 1998; Poulsen
et al., 2001). Insects make up nearly 30% of the diet at these
sites, with leaves and flowers each typically constituting about
5% of the diet. While the quantity of hard seeds eaten by
L. albigena varies by site and season in some places, seedeating makes up nearly 60% of feeding observations at the
Dja Reserve during the season that includes November and
December (Poulsen et al., 2001). Furthermore, recent mechanical properties testing has shown that grey-cheeked mangabeys
at Kibale consume more puncture-resistant foods (both seeds
and bark) than eaten by sympatric guenons at times of resource scarcity (Lambert et al., 2004). It is no wonder, then,
that these mangabeys can frequently be located in the forest
by the sound of crushing nuts (Waser, cited in Kay, 1981).
Papio ursinus is often considered a USO specialist, especially in the dry season. The chacma baboon sample used in
this study comes from the Transvaal Museum in Pretoria,
and has excellent provenience. Details can be found in Daegling and Grine (1999). These individuals were all collected
during the dry season from Messina and the D’nyala Reserve
in Limpopo Province, South Africa, and the Rustenburg Provincial Nature Reserve in Northwest Province, South Africa.
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
Hypogeous tubers, bulbs, and roots account for up to 90% of
the Papio ursinus diet at that time of year (Whiten et al., 1987,
1991; Byrne et al., 1993).
The human groups considered here have already been
documented to show diet/tooth-use-related differences in incisor microwear (Ungar and Spencer, 1999). All human specimens analyzed are housed at the U.S. National Museum of
Natural History. The Aleut included in this study were collected by Hrdlicka (1945) during his expeditions to the Aleutian
Islands. Most individuals studied are protohistoric, living after
AD 1700 (McCartney, pers. comm.). Ethnohistorical accounts
of Aleuts record an almost exclusively animal (mostly marine)
subsistence base, including both fresh and dried fish, mollusks,
and sea mammals. This diet was occasionally supplemented
with land resources, including rodents, foxes, and edible
tubers (Hrdlicka, 1945; Laughlin, 1963). The Aleut are well
known for their repetitive, high magnitude tooth-loading of animal tissues. Veniaminov (cited in Hrdlicka, 1945) noted, for
example, that the Aleut call the month of March Kisiagunak,
meaning ‘‘when they chew straps.’’
Most of the Arikara examined were collected by Stirling
from the Mobridge Site (39WW1) and probably date to AD
1600e1700 (Wedel, 1955; Jantz, 1973). The Arikara of the Mobridge Site made ample use of both plant and animal foods.
They had a mixed subsistence base, with animal and plant products each representing about half of the yearly diet. Plant foods
eaten included wild vegetation (e.g., black cherries, peppers,
grapes, pumpkin, and Chenopodium) and some cultigens
(maize, beans, squash, and sunflowers) (Hurt, 1969; Meyer,
1977; Blakeslee, 1994; Tuross and Fogel, 1994). Still, this
Plains group ate large amounts of bison, which were cut into
strips and dried (Meyer, 1977). They also hunted smaller
game, including deer, antelope, and jackrabbit. Thus, the two
foraging groups differed in degree of meat consumption, with
the Aleut relying much more on animal tissues than the Arikara.
Casting procedure
High resolution replicas of the fossil and baseline specimens were prepared following established procedures (Grine
and Kay, 1987; Teaford and Oyen, 1989c; Ungar, 1996).
Original teeth were cleaned with cotton swabs soaked in alcohol or acetone to remove dirt and preservatives as necessary.
Molds were then made of occlusal crowns using President’s
Jet regular body polyvinylsiloxane dental impression material
(Coltène-Whaledent Corp., Mawah, NJ), and allowed to
degas before casting. Replicas were then poured using
Epotek 301(Epoxy Technologies, Inc., Billerica, MA), a highresolution epoxy resin and hardener. Resulting casts were
mounted on aluminum SEM stubs with glyptal and colloidal
graphite (to ensure conductivity) and sputter-coated with approximately 20 nm of gold.
83
distance of 12e20 mm, and a magnification of 500!. Surfaces examined were oriented nearly perpendicular to the electron beam to minimize feature foreshortening (Gordon, 1988).
Crushing surfaces of early Homo permanent cheek teeth
that preserved antemortem microwear were recorded on Polaroid Type 55 Positive-Negative film. Analyses were restricted
to M1s and M2s for the baseline groups, and all available molars (and one P4) for the fossil samples (see Table 1). An ideal
study would be restricted to a single tooth type to minimize
analytical ‘‘noise’’ (Gordon, 1988; Bullington, 1991), but
this was not possible given the small sample sizes available
for early Homo. Inter-facet variation was controlled by restricting analysis to ‘‘Phase II’’ facets (Gordon and Walker, 1983).
These facets have been particularly effective in differentiating
primates by diet (Teaford, 1988a).
Specimens examined in this study combined variably worn
teeth, following usual practice. Previous analyses of dental microwear in early hominins have failed to find any relationship
between degree of gross wear and conventional microwear
measurements (Grine, 1986). Furthermore, recent work on
a sample of known-age wild primates has demonstrated no
age-related effects on microwear patterns (Nystrom et al.,
2004).
Photomicrographs were scanned at 200 DPI using a photo
scanner and cropped to 640 ! 480 pixels. Resulting images
had a resolution of 0.25 mm per pixel, and a sample area of
0.02 mm2 of the original occlusal surface. Two photomicrographs were taken for each specimen to increase the sample
area whenever sufficient microwear was preserved.
Data collection
Images were analyzed using Microware 4.02 (Ungar,
2002a). A mouse-driven pointer was used to define four points
for each feature: two each to identify the endpoints of the major and minor axes. Axis lengths and orientations were calculated, and standard descriptive statistics were recorded for
each image. Pits were distinguished from scratches on the basis of a 4:1 length to breadth ratio (Teaford, 1988a). Descriptive statistics presented here include: 1) overall feature
measurements (major and minor axis mean lengths and standard deviations), 2) percentage of all features that are pits;
3) pit measurements (length and width means and standard deviations); and 4) striation measurements (length and breadth
means and standard deviations and mean orientation vector
length).
All photomicrographs were digitized by three observers
(MFT, PSU, and SEZ). Values for individual specimens were
averaged to reduce measurement errors inherent in conventional dental microwear analyses (Grine et al., 2002; see discussion above).
Statistical analyses
Specimen imaging
Molar replicas were then examined using an Amray 1810
SEM at an accelerating voltage of 20e25 keV, a working
Statistical analyses focused on identifying significant microwear differences among baseline groups with known differences in diet, assessing microwear variation between
84
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
H. habilis and H. erectus, and determining how data for the
fossil species cluster relative to those for the baseline groups.
Four variables that have been shown in the past to be useful
for distinguishing living species with different diets were
considered here: 1) pit percentage, 2) striation breadth, 3)
pit width, and 4) mean orientation vector length (Walker
and Teaford, 1989; Ungar, 1994; Teaford et al., 2001; Rafferty et al., 2002).
Analyses of the baseline groups
All data were rank-transformed before analysis to mitigate
the possible effects of violating assumptions associated with
parametric statistical tests (Conover and Iman, 1981). Data
for the four variables were compared among species (based
on specimen values in Appendix II) using a multivariate analysis of variance model (MANOVA) with taxon as the dependent variable and measurement means for each individual as
the replicates (Neff and Marcus, 1980). Results indicated
whether the taxa differed significantly in overall microwear
patterning. Single classification ANOVAs on each variable
and multiple comparisons tests were used to determine sources of significant variation (Sokal and Rohlf, 1995). Because
baseline groups were chosen for their diet and expected microwear differences, Fisher’s least significant difference
(LSD) a priori tests were used to compare species. Tukey’s
honestly significant difference (HSD) post hoc tests were
also run to balance risks of Type I and Type II errors (Cook
and Farewell, 1996).
Differences between early Homo species
Rank-transformed microwear data for H. habilis, H. erectus, and the early Homo specimens from Sterkfontein Member
5C and Swartkrans Member 1 were compared using the same
MANOVA scheme described above for comparisons of baseline groups. Only variables that showed significant variation
among baseline groups were included in this analysis. The
ANOVAs for each variable were used to determine sources
of significant variation, and Tukey’s HSD post hoc tests
were used to compare pairs of taxa.
Comparisons of the fossil data and the baseline series
Hierarchical cluster analyses were performed on the living
and fossil taxa, using each of the microwear variables that
showed significant variation among taxa in the ANOVA models. Variables were considered separately because they evince
different scales. Euclidean distance and complete linkage were
used, following Fortelius and Solounias (2000). Specimens assigned to H. habilis and H. erectus and samples from Sterkfontein Member 5C and Swartkrans Member 1 were considered
separately.
Results
Raw data for average feature dimensions, pit percentages,
and pit and striation measurements for each specimen are presented in Appendix II. Example photomicrographs are illustrated in Fig. 1. Summary statistics are presented in Table 2
and illustrated in Figs. 2e4. Results of statistical analyses
are given in Tables 3e4.
The baseline series
Results of statistical analyses for the baseline sample are
presented in Table 3. All MANOVA test statistics indicate significant variation in the model. In other words, microwear patterns vary among the taxa. Individual ANOVAs show
significant variation in feature sizes (both pit width and striation breadth) and pit percentage. The taxa do not differ in striation mean vector length (i.e., orientation homogeneity).
Multiple comparisons tests show the sources of the observed variation. First, pit widths indicate clusters of baseline
groups. Gorilla, Cebus, and Pan cluster together as one group,
and Arikara, Lophocebus, Papio, and Aleut cluster in the other.
In nearly all cases, each member of one group differs significantly from each member of the other according to both Fisher’s LSD and Tukey’s HSD test results. Striation breadths also
discriminate between two groups, which are the same as those
for pit width, except that the Arikara cluster with Gorilla,
Cebus, and Pan rather than with the Aleut, Papio, and Lophocebus. Differences between the Aleut and those samples with
narrower striations are only marginally significant. These
groupings are clearly illustrated by the hierarchical cluster
analyses (see Fig. 4).
The multiple comparisons results for the pit percentage
analysis indicate three groups, although these are not as clearly
separated as are the two groups identified for the feature size
variables: 1) Cebus and Lophocebus, 2) Aleut, Pan, and Papio,
and 3) Gorilla and Arikara. Cebus and Lophocebus have the
highest mean pit percentage values, whereas Gorilla and
Arikara have the lowest values (i.e., the highest proportion of
striations). Pit percentages differ significantly between taxa
in different groups but not within these groups. Thus, these
two groups can be clearly separated. The Aleut, Pan, and Papio
samples have intermediate values. All three differ from Gorilla
(though Pan only marginally), Arikara differs marginally from
Papio, and Pan differs from Cebus and Lophocebus. The
Aleut-Pan-Papio group may be considered tenuous because
Papio does not differ significantly from Cebus or Lophocebus,
and Pan does not differ from the Arikara sample. Still, these
groupings are supported by the cluster analyses presented in Fig. 4.
In sum, the baseline samples fall into six groups on the
basis of pit percentage and feature size (Fig. 3). The mangabeys have high pit percentages and large features, the baboons
and Aleuts have intermediate pit percentages and large features, the capuchins have high pit percentages but smaller features, the chimpanzees have intermediate pit percentages and
small features, and the gorillas have low pit percentages and
small features. The Arikara have low pit percentages, with
large pits but narrow striations on average.
Early Homo comparisons
Results comparing the four hominin groups are presented
in Table 4. The MANOVA results indicate significant
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
85
Fig. 1. Representative photomicrographs of ‘‘Phase II’’ molar facets for groups considered in this study: A) Lophocebus albigena (NMNH 220086), B) Cebus
apella (NMNH 296634), C) Homo erectus (KNM-ER 820), D) Papio ursinus (AZ 45), E) Aleut (NMNH 377913), F) Pan troglodytes (CMNH B-3437),
G) Homo habilis (OH 15), H) Arikara (NMNH 315539), I) Gorilla gorilla (NMNH 545027). The scale bar Z 30 mm.
variation in the model. The ANOVA tests indicate significant
variation in pit percentage but not pit width or striation
breadth. Pairwise comparisons indicate that H. erectus from
eastern Africa and Swartkrans Member 2 have higher pit percentages than do H. habilis from eastern Africa and Sterkfontein Member 5A. Likewise, specimens from Swartkrans
Member 1 have higher pit percentages than do those from
Sterkfontein Member 5C. On the other hand, pit percentages
for Sterkfontein Member 5C do not differ significantly from
those for H. habilis (from eastern Africa and Sterkfontein
Member 5A), and those for Swartkrans Member 1 do not differ significantly from those for H. erectus (from eastern
Africa and Swartkrans Member 2).
Figure 4 presents the hierarchical cluster analyses for each
variable, including data for the baseline groups and using the
fossil specimen attributions listed in Appendix II. There are
two distinct clusters for pit width. Papio, Lophocebus, and
the Aleut (those taxa with the largest pits) are clearly separate
from all other taxa, including the fossil hominins. There may
also be a second-order pit width clustering that separates
H. habilis, Sterkfontein Member 5C specimens, Arikara, and
Pan from Gorilla, Cebus, H. erectus, and Swartkrans Member
1 specimens. This clustering is supported by a significant difference between Arikara on the one hand and Cebus and
Gorilla on the other. On the other hand, the lack of significant variation among the hominins, or between Pan, Cebus,
and Gorilla makes this unlikely.
There are also two distinct clusters for striation breadth.
These clusters accord well with those suggested by statistical
analyses of striation breadth for the baseline series. Papio,
Lophocebus, and the Aleut all have thicker striations on average than do the other samples. There may, in addition, be a second-order striation breadth cluster separating the Aleut from
Papio and Lophocebus. The lack of significant differences between the Aleut and either the baboons or mangabeys makes
this unlikely, however. All of the hominins have lower mean
striation breadth values, clumping together with Cebus, the
Arikara, Pan, and Gorilla.
Finally, there are also two distinct clusters for pit percentage. Homo habilis and Sterkfontein 5C specimens cluster
with the Arikara and Gorilla samples, separate from all other
groups analyzed. There also appears to be a secondary
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
86
Table 2
Descriptive microwear statistics*
60
50
40
30
Aleut
(n Z 5)
X
s
18.5
3.95
3.3
0.50
6.3
1.07
1.5
0.21
0.54
0.086
45.9
10.01
Arikara
(n Z 5)
X
s
27.0
11.15
2.1
0.68
4.9
1.30
1.3
0.24
0.45
0.213
30.8
19.37
Cebus
(n Z 5)
X
s
11.1
2.22
2.2
0.41
3.2
0.65
1.2
0.14
0.49
0.196
59.1
8.74
Gorilla
(n Z 5)
X
s
29.7
4.64
1.7
0.44
2.8
0.61
1.3
0.36
0.56
0.185
25.5
9.32
Lophocebus
(n Z 5)
X
s
16.0
2.95
4.3
1.07
5.8
1.07
1.9
0.23
0.56
0.131
59.2
11.03
Pan
(n Z 5)
X
s
18.8
5.98
2.2
0.38
3.7
1.12
1.2
0.09
0.49
0.190
43.7
5.08
Papio
(n Z 5)
X
s
17.9
3.51
3.8
1.40
5.9
0.99
1.8
0.81
0.47
0.083
48.4
16.36
H. habilis
(n Z 6)
X
s
23.8
6.07
2.4
0.53
4.1
1.06
1.3
0.15
0.54
0.092
37.5
5.99
H. erectus
(n Z 5)
X
s
15.0
3.34
2.2
0.30
3.1
0.63
1.3
0.12
0.48
0.124
50.2
4.47
Sterk M. 5
(n Z 3)
X
s
22.3
4.77
2.4
0.63
4.0
0.86
1.4
0.26
0.51
0.065
36.2
12.68
2
Swart M. 1
(n Z 4)
X
s
15.8
0.95
2.3
0.23
3.3
0.14
1.3
0.125
0.40
0.120
50.1
4.88
1.75
1.5
20
10
Lo
ph
oc
eb
us
Ce
bu
s
Al
eu
t
Pa
n
Pa
pi
o
G
or
ill
a
0
7
6
Pit Width
5
4
3
2
1
eu
t
o
Al
pi
eb
oc
1.25
1
0.75
0.5
Discussion
The results presented here for the fossil hominins can be interpreted in terms of relationships between diet and microwear
for the baseline series. Interpretations can then be considered
relative to those derived from other lines of evidence, and
used to evaluate recent models for the diets of early Homo.
us
o
eb
pi
Lo
ph
oc
Pa
t
eu
Al
a
G
or
ill
a
ar
ik
Ar
Pa
bu
Ce
clustering of H. erectus and the Swartkrans Member 1 specimens with the Aleut, Pan, and especially Papio. This cluster
appears to be distinct from Lophocebus and Cebus. This second-order clustering does accord well with those suggested
by statistical analyses of pit percentage in the baseline series.
n
0.25
0
s
* Means (X ) and standard deviations (s) for feature lengths (major and minor
axes), pit and striation breadths, striation orientation concentration (r), and
percentage incidence of pitting (taxon averages). All linear measurements
are in mm. See Appendix II for information on individual specimens.
Striation Breadth
Lo
ph
Pa
us
a
ar
ik
Ar
G
or
ill
a
0
Pa
n
Pit
%
ik
ar
a
Scratch
r
Ar
Scratch
breadth
s
Pit
width
bu
Minor
length
Ce
Major
length
Pit Percentage
Group
70
Fig. 2. Microwear pit percentage (top), pit width (middle), and striation
breadth (bottom) mean values for baseline groups.
diets. Theory dictates that microwear feature linearity should
reflect the angle of approach of opposing facets, and that the
angle of approach should reflect the mechanical properties
of foods to be fractured (Grine, 1981). Opposing facets that
Interpretation of the microwear results
The baseline series
The baseline groups varied in microwear pit percentages,
pit widths, and striation breadths. Some of these differences
provide insights into the relationships between microwear
and diet in nonhuman primates and foraging peoples that
can be used to infer aspects of diet in early Homo.
Pit percentage is the most widely and successfully used microwear attribute for distinguishing mammals with different
Fig. 3. Distinguishing microwear criteria for baseline groups. 1Arikara have
large pits; 2Arikara have broad striations.
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
87
Lophocebus
Cebus
H. erectus
Swartkrans 1
Papio
Table 3
Extant primate microwear comparisons
A. MANOVA results
Aleut
Pan
Wilks’ l
Statistic
0.059
df
24, 88
F
P
4.609
0.000
B. Individual ANOVAS
H. habilis
Sterkfontein 5
Arikara
Gorilla
0
10
20
30
40
Pit Percentage Distances
Aleut
Papio
Lophocebus
Arikara
H. habilis
Sterkfontein 5
Effect
SS
df
MS
F
P
Pit width
Error
2458
1112
6
28
410
40
10.313
0.000
Striation breadth 2083
Error
1485
6
28
347
53
6.544
0.000
Striation r
Error
220
3350
6
28
37
120
0.307
0.928
Pit percentage
Error
2042
1528
6
28
340
55
6.239
0.000
C. Multiple comparisons tests (matrices of pairwise mean differences)
Pit width
Pan
Swartkrans 1
Cebus
H. erectus
Gorilla
Arikara
Cebus
Gorilla Lophocebus
Pan
7.6
20.2z 12.6z
22.1z 14.5z
3.4
4.2
17.3z 9.7y
3.6
4.0
1.9
16.8z
2.9
16.6z
18.7z
4.8
18.5z
13.7z
Aleut
Arikara
Cebus
Gorilla Lophocebus
Pan
1.6
3.2
20.9z
2.7
15.5z
1.6
19.3z
1.1
13.9y
17.7z
0.5
12.3y
12.8y
Arikara
Cebus
Gorilla Lophocebus
Pan
21.2z
10.2y
14.8z
4.6
Aleut
0
1
2
3
4
Pit Width Distances
Cebus
Arikara
Pan
Arikara
Cebus
Gorilla
Lophocebus
Pan
Papio
13.9z
0.2
Striation breadth
Gorilla
H. erectus
Swartkrans 1
Arikara
Cebus
Gorilla
Lophocebus
Pan
Papio
H. habilis
Sterkfontein 5
Aleut
Papio
Lophocebus
14.2y
12.6y
11.0y
6.7
11.5y
1.3
18.2z
5.4
Percent pitting
Aleut
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Striation Breadth Distances
Fig. 4. Hierarchical cluster analyses for baseline and fossil groups: pit percentage (top), pit width (middle), and striation breadth (bottom) mean values for
baseline groups. See Appendix II for fossil specimen designations.
Arikara
Cebus
Gorilla
Lophocebus
Pan
Papio
y
shear past one another to slice tough foods should be dominated by scratches from abrasives that are dragged along tooth
surfaces. In contrast, opposing facets that approach perpendicular to one another to crush hard, brittle foods should be dominated by pits. Indeed, many studies have shown that mammals
that prefer hard, brittle foods have higher pit percentages than
those that usually eat soft, tough items (Teaford and Walker,
1984; Teaford, 1988a; Van Valkenburgh et al., 1990; Strait,
1993; Crompton et al., 1998).
The pit percentage results presented here make sense given
documented differences in diet and subsistence practices.
Cebus apella and L. albigena, for example, have high pit percentages, as expected for seasonal ‘‘hard-object’’ feeders
(Terborgh, 1983; Janson and Boinski, 1992; Poulsen et al.,
2001; Lambert et al., 2004). Gorilla gorilla beringei
z
9.0
9.2
13.0y
8.2
2.8
1.8
18.2z
4.0 22.2z
17.2z 1.0
6.2 12.0y
10.8y 7.4
11.0y
6.4
Fisher’s LSD test p % 0.05.
Fisher’s LSD and Tukey’s HSD test p % 0.05.
specimens have low pit percentages (i.e., high striation
counts), as expected for primates with diets dominated by
tough leaves and stems (Fossey and Harcourt, 1977; Vedder,
1984; Watts, 1990; Elgart-Berry, 2004). Pan troglodytes individuals are intermediate in microwear pit percentage, and are
intermediate in the average fracture properties of the foods
they consume (Tutin and Fernandez, 1985; Kuroda, 1992; Tutin et al., 1997). Papio ursinus pit percentages are also intermediate in mean pit percentage, though they do not differ
significantly from C. apella or L. albigena. This result is consistent with seasonal consumption of USOs (Whiten et al.,
1987; Whiten et al., 1991; Byrne et al., 1993), assuming that
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
88
Table 4
Early Homo microwear comparisons
A. MANOVA results
Statistic
df
F
P
0.172
9, 29
3.455
0.005
SS
df
MS
F
P
Pit width
Error
154.0
330.5
3
14
51.333
23.607
2.174
0.137
Striation breadth
Error
46.8
437.7
3
14
15.600
31.264
0.499
0.689
Pit percentage
Error
364.5
120.0
3
14
121.500
31.264
14.175
0.000
Wilks’ Lambda
B. Individual ANOVAS
Effect
C. Multiple comparisons tests
Percent pitting
Homo habilis
Sterkfontein M. 5C
Swarktrans M. 1
z
Homo
erectus
Homo
habilis
Sterkfontein
M.5
9.400z
8.500z
0.000
0.900
9.400z
8.500z
Tukey’s HSD test p % 0.05.
they are hard and brittle or coated with large-grained exogenous grit (Daegling and Grine, 1999). The results for all of
these taxa are consistent with previous studies of microwear
(Teaford and Walker, 1984; Teaford, 1988a; Daegling and
Grine, 1999).
The human samples may also be understood in this context.
While pit percentage values do not differ significantly between
the groups, the high variance in the Arikara values probably
correlates with their greater dietary variation (Hrdlicka,
1945; Laughlin, 1963; Blakeslee, 1994; Tuross and Fogel,
1994), which, in turn, may have masked differences between
these groups, especially given the small samples analyzed
here. The significant difference between the Arikara and
Cebus, Lophocebus, and Papio is noteworthy because of the
lack of difference in pit percentage between the Aleut, Cebus,
and Lophocebus. Indeed, the Aleut were expected to cluster
with Cebus and Lophocebus because repetitive loading and
forceful chewing may also cause pits (Puech et al., 1981,
1983b; Teaford and Oyen, 1989a; Teaford and Runestad,
1992; Rafferty et al., 2002). This result may be consistent
with Spencer and Ungar’s (2000) suggestion, based on differences in craniofacial morphology, that the Aleut probably engaged in more powerful or repetitive loading than did the
Arikara.
Two groups were distinguished on the basis of pit width: 1)
Gorilla, Cebus, and Pan and 2) the Arikara, Lophocebus,
Papio, and Aleut. These pit width results need to be interpreted within the context of the etiology of the individual features. Early experimental work (Puech et al., 1981, 1985)
hinted at two primary patterns of antemortem microwear pitting: larger impact craters caused by hard objects, and smaller
pits caused by adhesive wear. Subsequent research clarified the
relationships between pit size and etiology. For example, laboratory work with monkeys suggested a possible link between
hard foods and large pits (Teaford and Oyen, 1989a), and studies of museum samples of geladas and chacma baboons suggests that these ‘‘hard objects’’ might well include
exogenous grit on foods (Teaford, 1993; Daegling and Grine,
1999). Studies of interstitial and canine-honing facets indicated that tooth-tooth wear (attrition) can lead to the formation
of smaller, prism-sized pits (Walker, 1984; Radlanski and
Jager, 1989). Teaford and Runestad (1992) suggested that differences in pit size might then help to distinguish between primates whose diets include hard, brittle items and those whose
diets comprise tough foods, with the former showing larger
microwear pits. More recently, Rafferty et al. (2002) showed
high incidences of prism-sized microwear pits for primate species that routinely feed on tough foods.
According to this interpretation, Gorilla and Pan should
have smaller pits than Lophocebus and Papio, and they do.
On the other hand, C. apella should have larger pits than the
apes, as was reported by Teaford (1988a) in an earlier study.
They do not. Either pit size is not as good a marker as might
be expecteddi.e., the large number of features in Cebus apella
effectively swamps the signal from large pitsdor the individuals studied here were collected at a time or place when they
were feeding on tough rather than hard-brittle foods. Small absolute body size (and consequent low maximum occlusal
force) does not explain the small pit size in C. apella, as there
does not appear to be a relationship between primate body
mass and microwear feature dimensions, even within broad dietary categories (e.g., Teaford, 1988a). We expect that studies
of larger samples using new 3-D microwear analysis techniques (Ungar et al., 2003) will help resolve this issue.
The Arikara and especially the Aleut have large pits on average, which suggests that their pits were formed as a result of
high-impact crushing rather than attritional shearing and slicing. Because the Arikara diet is so varied, it is difficult to parse
microwear signals related to specific items. The Aleut, on the
other hand, had a diet dominated by meat, which is generally
recognized to be tough, requiring substantial work to fracture
(Lucas and Peters, 2000). While meat itself is too soft to indent enamel, tooth wear may result from adherent grit (Lalueza et al., 1996; Ungar and Spencer, 1999), or the
adhesive effects of tooth-on-tooth contacts during mastication
(Puech et al., 1981, 1985). Large microwear pits in the Aleut
sample more likely resulted from high occlusal forces (Spencer and Ungar, 2000) in combination with hard abrasives
clinging to food, much like the situation posited for coastal
hunter-gatherers in North America (Teaford et al., 2001).
The Cebus, Pan, Gorilla, and Arikara samples had narrower striations on average than did the Aleut, Papio, and
Lophocebus samples. These differences are likely due to
a combination of factors, including the sizes and shapes of
abrasive particles, the magnitudes of occlusal forces, and perhaps even differences among the groups in underlying enamel
structure (Maas, 1991). The most common way to scratch
a tooth is to drag across it an object harder than enamel (Moh’s
hardness from 4.5 to 5.0). Two likely culprits are 1) silica in
exogenous grit from dust or soil (Moh’s hardness of quartz
is 7.0) and 2) opal phytoliths, which are formed as monosilicic
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
acid is absorbed from groundwater and deposited in the cell
walls of plants that are eaten (Moh’s hardness from 5.5 to
6.5) (Baker et al., 1959; Lucas and Teaford, 1995; Ungar
et al., 1995; Lucas, 2004; Teaford et al., in press). Microwear
striation breadths are likely limited by the sizes and shapes of
these abrasives (Ungar, 1994; Ungar and Spencer, 1999).
Larger phytoliths could leave broader striations than expected
from exogenous grit dominated by smaller, angular clay grains
(Ungar, 1994), though larger-grained sand particles could also
yield thicker scratches (Daegling and Grine, 1999; Teaford
et al., 2001).
Occlusal force likely also plays a role in striation breadth.
We know, for example, that hard-object feeders tend to have
wider microwear striations than those that prefer softer fruits
and leaves (Teaford, 1988a). Ryan’s (1981) attribution of thick
gouges in Inuit incisors to ‘‘power grasping/pulling’’ activities
is consistent with this notion. This factor might explain why
the Aleut have broader striations than the Arikara (Ungar
and Spencer, 1999), and perhaps why Papio and especially Lophocebus have broader striations than Pan. On the other hand,
it remains unclear why Cebus striations are narrower. Until we
better understand the factors that influence striation breadth,
interpretations of differences between groups as diverse as
those sampled here will remain limited (Teaford and Runestad,
1992).
The fossil groups
The extant baseline data indicate that higher pit percentages
should reflect consumption of hard, brittle items requiring
heavy masticatory loads. Larger pits suggest hard, brittle items
whereas smaller pits more likely point to tougher foods and
adhesion of opposing surfaces during shearing. The hominins
are well separated from Papio, Lophocebus, and the Aleut in
both striation breadth and pit width. The Aleut, chacma baboons, and mangabeys consume foods that evidently require
considerable occlusal force for comminution, such as tough
mammalian tissues,2 tough seeds and corms, and, in the case
of the mangabeys, at least occasional hard and brittle nuts.
This makes sense given inferred relationships between occlusal force and pit size and striation breadth. Compared with the
Aleut, Lophocebus, and Papio, the early Homo groups probably did not typically eat foods with considerable fracture
strength or puncture resistance. These fossil hominins therefore likely did not specialize on extremely tough foods, such
as dried meat, or those with extremely high yield strengths,
such as hard USOs.
Likewise, none of the fossil hominin groups have the high
pit percentages of L. albigena or C. apella. This result also
suggests that early Homo did not often consume hard objects.
Homo habilis and Sterkfontein Member 5C specimens have
relatively low pit percentages, in line with the figures for the
2
Occlusal forces required to fracture a food item depend on both mechanical properties of that food and tooth shape (Lucas, 2004). Tough, dried meat,
for example, should require more forceful and repeated chewing cycles to fracture by flat Aleut molars than by steeply sloped teeth, such as carnassials designed for shearing and slicing such foods.
89
Arikara and Gorilla. This result implies a diet that included
some tougher foods, such as those with the mechanical properties of some leaves, woody plants, and perhaps some animal
tissues. In contrast, H. erectus and Swartkrans Member 1
specimens had higher but still moderate pit percentages, in
line with those of the Aleut, Pan, and especially Papio. This
result implies consumption of a range of items and/or those
with intermediate fracture properties. These early hominins
may have eaten some more resistant foods, such as harder
USOs or tough animal tissues than did H. habilis or the hominins from Sterkfontein Member 5C.
The lack of differences in feature size between the early
hominin samples suggests that microwear feature ‘‘types’’
may have been formed by similar processes. Small samples
and the dietary versatility that might be expected of early
Homo (Teaford et al., 2002; Wood and Strait, 2004) would
make it difficult to detect differences between the taxa. However, the fact that feature size variation within these samples is
not especially large may reflect comparable balances between
abrasive particle size and masticatory force rather than Type II
statistical errors.
In contrast, the significant differences in pit percentage suggest that the early Homo individuals differed in the fracture
properties of their diets. Higher pit percentages for H. erectus
and the individuals from Swartkrans Member 1 imply at least
occasional consumption of significantly harder or tougher
foods on average than those eaten by H. habilis and the individuals from Sterkfontein Member 5C. The fact that these pits
tend to be small suggests that they were formed by adhesive
wear during shearing and slicing, and therefore that H. erectus
and the individuals from Swartkrans Member 1 consumed
tougher foods on average than the other samples. Still, because
of the small features found in the C. apella sample analyzed
for this study, we cannot exclude the possibility that those
hominins with higher pit percentages actually consumed
some harder foods or ingested larger-grained abrasives as
well. Further work on larger samples of extant taxa using
3D microwear texture analysis (Ungar et al., 2003) will hopefully allow us to resolve this issue.
Implications of the microwear results
Changes in diet through time
Comparisons of the early Homo samples to one another allow us to speculate on whether microwear can offer insights
into changes in diet through time. Although it is difficult to define ancestor-descendant relationships between specific fossil
taxa with precision, H. habilis does make a reasonable ancestral morphotype for the genus Homo, including H. erectus
(Chamberlain and Wood, 1987; Strait et al., 1997; Kimbel
et al., 1997). In the present context, some features of possible
relevance to this argument include retention of larger molars
and perhaps thicker tooth enamel than observed for H. erectus
(Teaford et al., 2002). Wood and Collard (1999) have even argued that H. habilis is plesiomorphic enough to belong to the
australopith adaptive grade, and should be reassigned to the
genus Australopithecus.
90
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
In this sense then, a direct comparison of microwear in
these species might provide new insights into changes in
diet within the genus Homo around the time of the PlioPleistocene boundary. If so, similarities in feature size suggest
that the abrasives causing microwear pits and striations
remained consistent over time. However, the material properties of foods eaten may have changed. Higher pit percentages
in H. erectus suggest that these hominins may have incorporated increasing amounts of fracture-resistant foods (possibly
hard, but more likely very tough) compared with H. habilis.
Early Homo samples from Sterkfontein Member 5C and
Swarktrans Member 1
Samples from Sterkfontein Member 5C postdate those from
Member 5A assigned to H. habilis (Partridge, 2000). Indeed,
apparent morphological similarities between Member 5C
specimens and those from Swartkrans Member 2 have suggested to some that they belong to what we refer to as H. erectus (Kuman and Clarke, 2000). In contrast, Swartkrans
Member 1 specimens predate those from Member 2 assigned
to H. erectus. Grine (2005) proposed that Member 1 hominins
more closely resemble H. habilis than they do H. erectus. Regardless of the specific attributions of these samples, there
seems to be continuity in microwear pattern within each of
these South African localities. In other words, the microwear
patterns of H. habilis specimens from eastern Africa and
Sterkfontein Member 5A are very similar to those from Sterkfontein Member 5C. Likewise, H. erectus specimens from
eastern Africa and Swartkrans Member 2 have microwear patterns indistinguishable from those of the Swartkrans Member
1 hominins.
Comparisons with previous studies
Previous microwear studies
Early Homo microwear results presented here can also be
interpreted within the context of results from previous studies
and other lines of evidence for the diets of these hominins.
Data presented here may be consistent with the preliminary
microwear results presented by Waddle (1988), which suggested that early Homo from Swartkrans Members 1 and 2
had a high incidence of small pits. Heavy pitting in H. erectus
from eastern Africa was also suggested by Walker (cited in
Waddle, 1988; Walker and Shipman, 1997). Still, while our results suggest that H. erectus and the sample from Swartkrans
Member 1 had higher incidences of small pits than did H. habilis or the specimens from Sterkfontein Member 5C, none of
these hominins showed an extremely high incidence of pitting
or remarkably small pits. Thus, the fracture properties of their
diets were probably not as challenging as earlier studies suggested. Puech et al. (1983a) and Puech (1984) also studied microwear in some early Homo specimens, speculating that
evidence of erosion of H. habilis molars from Olduvai Gorge
(no list of specimens was provided) indicates acidic fruit consumption. However, more recent studies have shown that the
pattern of erosion described by these authors suggests taphonomic damage to the part of the tooth examined rather than
antemortem tooth use (see Teaford, 1988b; King et al.,
1999). The specimens in question are much more severely
eroded than any of the extant baseline teeth, and we found evidence of this erosion on both occlusal facets and non-occlusal
parts of the teeth, including interstitial facets not exposed to
food during life.
Other lines of evidence
Bone and tooth chemistry, like microwear, tells us something about what an individual ate. Whereas microwear indicates possibly only a few weeks of diet (Teaford and Oyen,
1989b), tooth and especially bone chemistry reflects food preferences averaged over many months to many years. It is not
surprising then, that preliminary results published for the stable isotopes d13C and d18O for the Swartkrans Member 1
Homo sample suggest a generalized diet (Lee-Thorp et al.,
2000; van der Merwe et al., 2003). Indeed, intermediate microwear pit percentages for these hominins accord well with
a mixed or generalized diet, as does the lack of large average
feature sizes that are seen in some dietary specialists.
The other two commonly cited lines of evidence for diet in
early Homo, tooth size and shape, provide evidence of what
a taxon (or its ancestor) may have been adapted to consume
rather than what an individual actually ate. We prefer to leave
the studies of dental allometry until larger samples and more
precise body weight estimates are available, and relationships
between molar size and function are better understood (see
Ungar et al., in press). Molar shape, on the other hand, has
provided some interesting clues. While sample sizes have
necessitated combining taxa, early Homo specimens show
moderately sloped occlusal surfaces, suggesting an adaptation
to a diet tougher than that of their australopith predecessors,
and intermediate between those of chimpanzees and gorillas
(Ungar, 2004). This is also consistent with the intermediate
microwear pit incidences found in early Homo.
Dental microwear and diet models
The microwear results presented here, combined with other
lines of evidence, suggest that early Homo ate foods that were
neither extremely hard nor exceedingly tough, but instead consumed a rather varied diet. Further, while the diets of different
early Homo groups probably did not differ dramatically from
one another, H. erectus and individuals from Swartkrans Member 1 probably consumed some foods that were more difficult
to fracture than did H. habilis and the individuals from Sterkfontein Member 5C.
These interpretations allow us to comment on popular models for early Homo diets. Researchers have long argued that
a new resource base made available by the spread of C4 grasslands and stone tools motivated subsistence changes that led to
the origin and early evolution of our genus (for review, see Ungar et al., in press). Workers have suggested a shift from a diet
dominated by fruit or other forest resources to savanna animals
or xeric plants (especially USOs). In this light, the lack of microwear evidence for dietary specialization is instructive. None
of these hominins probably limited their diets to either tough
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
meat or hard USOs. On the other hand, microwear differences
between H. habilis and H. erectus may be of some significance,
especially if the higher incidences of pitting in the latter reflect
consumption of more foods resistant to fracture.
Ungar (2004) suggested that the diets of early Homo and
their immediate predecessors differed largely in fallback foods
consumed during times of resource stress. He measured the
average difference in occlusal slope between Australopithecus
afarensis and early Homo molars at a given stage of wear to be
4.1 degrees. This is comparable to that between sympatric
chimpanzees and lowland gorillas (with an average difference
of 4.3%; Ungar, 2004), taxa that overlap greatly in their diets
except at ‘‘crunch’’ times. The intermediate pattern of microwear makes sense in this light because features may turn over
rapidly (Teaford and Oyen, 1989b), and thus should reflect
more commonly eaten foods. Extant primates often prefer
foods that are easy to fracture, leaving tougher or harder items
as occasional fallback resources (e.g., Remis, 1997; Lambert
et al., 2004). It is reasonable to hypothesize, then, that early
Homo species had versatile diets, but preferred foods that
were easy to consume. These hominins, especially H. erectus
and the individuals from Swartkrans Member 1, would probably have resorted to harder or tougher items mostly when other
foods were unavailable. We speculate that, given environmental dynamics during the Plio-Pleistocene (Cerling, 1992;
Behrensmeyer et al., 1997; Potts, 1998), changes in the fracture properties of fallback foods consumed by early Homo
might relate to changes in resources available to these
hominins.
Conclusions
A study of early Homo from the Plio-Pleistocene of eastern
and southern Africa reveals antemortem microwear on molars
or premolars of 18 of 83 specimens examined. Microwear
data for these specimens cluster with data for baseline groups
of protohistoric human foragers and extant nonhuman primates that prefer less fracture-resistant foods. This finding
suggests that none of the early Homo groups specialized on
very tough or very brittle items. Still, H. erectus and Swartkrans Member 1 specimens do have more small pits than do
those of H. habilis and specimens from Sterkfontein Member
5C. This result suggests some dietary variation among these
early hominins such that H. erectus and individuals from
Swartkrans Member 1 ate, at least occasionally, more tough
or brittle foods than did H. habilis and individuals from Sterkfontein Member 5C.
Acknowledgements
We thank the curators at the National Museums of Kenya
and Tanzania, the University of the Witwatersrand, the Transvaal Museum, U.S. National Museum of Natural History, and
the Cleveland Museum of Natural History for permission to
study collections in their care. We are grateful to Alejandro
91
Pérez-Pérez for his help collecting impressions of the hominin
teeth in Kenya, Tanzania, and South Africa and to Tim Bromage for the replica of the Uraha specimen. We also thank Mike
Plavcan and Rob Scott for advice on statistics, and the anonymous reviewers and Bill Kimbel for their helpful comments
on an earlier version of this paper. This project was funded
by NSF SBR 9804882.
Appendix I. Fossil specimens examined for this study
AL 666-1
DNH 70
KNM-BK 67
KNM-BK 8518
KNM-ER 730
KNM-ER 806
KNM-ER 807
KNM-ER 808
KNM-ER 809
KNM-ER 820
KNM-ER 992
KNM-ER 1462
KNM-ER 1480
KNM-ER 1482
KNM-ER 1483
KNM-ER 1502
KNM-ER 1506
KNM-ER 1507
KNM-ER 1508
KNM-ER 1590
KNM-ER 1801
KNM-ER 1802
KNM-ER 1805
KNM-ER 1808
KNM-ER 1812
KNM-ER 1813
KNM-ER 1814
KNM-ER 2597
KNM-ER 2600
KNM-ER 2601
KNM-ER 3733
KNM-ER 3734
KNM-ER 3953
KNM-ER 15960
KNM-WT 15000
Lainyamok
OH 4
OH 6
OH 7
OH 13
OH 15
OH 16
OH 27
OH 37
OH 39
OH 41
OH 45
OH 60
OH 62
Omo 166-1973-781
Omo 166-781
Omo 195-1973-1630
Omo 35-1973-4023
Omo 75-1969-14
Omo 75s-1969-15
Omo 75s-1969-16
Omo K 7-1969-19
Omo L 26-1G
Omo L 28-30
Omo L 398-573
Omo L 894-1
Omo P 933-1
Omo SH1.1-1969-17
SE 255
SE 1508
SE 1579
SK 15
SK 27
SK 45
SK 847
SK 2635
SKX 257
SKX 268
SKX 334
SKW 3114
Sts 19
Stw 19b
Stw 53
Stw 80
Stw 81
Stw 82
Stw 103
UR 501
AL Z Hadar; DNH Z Drimolen; KNM-BK Z Baringo; KNM-ER Z Koobi
Fora; KNM-WT Z West Turkana; OH Z Olduvai Gorge; Omo Z Shungura;
SE, Sts, Stw Z Sterkfontein; SK, SKX, SKW Z Swartkrans, UR Z Uraha,
Malawi.
Appendix II. Phase II facet microwear summary statistics
Group
Specimen*
Pits
(%)
Axis
lengths
Pits
Striations
Major Minor Len Wid Len Wid
Aleut
r
NMNH
NMNH
NMNH
NMNH
NMNH
377852
378618
377803
377913
378283
45.1
44.8
51.5
30.5
57.3
17.0
16.8
18.1
25.3
15.2
3.3
3.9
3.3
2.5
3.3
6.7
11.8
6.6
8.2
7.1
5.9
8.2
6.2
5.9
5.5
25.6
21.3
27.3
33.4
25.5
1.8
1.6
1.6
1.4
1.3
0.40
0.55
0.48
0.61
0.44
Arikara NMNH
NMNH
NMNH
NMNH
NMNH
324718
325339
325351
315539
382912
10.7
38.6
60.5
20.6
23.6
42.1
22.3
12.2
32.3
26.1
1.4
2.7
2.6
2.7
1.4
5.4
8.3
5.2
9.3
4.4
4.6
6.1
4.2
6.4
3.3
46.3
31.2
20.1
38.8
31.1
1.2
1.0
1.2
1.6
1.0
0.71
0.59
0.40
0.15
0.42
(continued on next page )
P.S. Ungar et al. / Journal of Human Evolution 50 (2006) 78e95
92
Appendix II (continued)
Group
Specimen*
Pits Axis lengths
Pits
Striations
(%) Major Minor Len Wid Len Wid r
Cebus
apella
NMNH
NMNH
NMNH
NMNH
NMNH
296634
296640
406443
406624
406627
52.3
66.4
67.1
47.5
62.0
10.2
7.7
12.6
13.2
11.8
2.1
1.7
2.4
2.1
2.8
5.0
3.8
4.9
6.1
6.7
3.1
2.2
3.1
3.5
4.0
15.4
13.6
26.7
18.1
19.4
1.0
1.0
1.3
1.2
1.2
0.45
0.17
0.57
0.64
0.62
Gorilla
gorilla
NMNH
NMNH
NMNH
NMNH
NMNH
545027
545029
545031
545034
545036
27.9
29.2
30.1
9.0
31.3
28.5
27.6
29.7
37.4
25.1
1.5
1.8
2.4
1.2
1.7
4.5
5.3
6.6
3.7
5.0
2.8
3.2
3.5
1.9
2.8
38.0
36.7
40.2
40.6
34.2
1.0
1.2
1.9
1.1
1.2
0.75
0.55
0.69
0.52
0.27
Lophocebus
albigena
NMNH
NMNH
NMNH
NMNH
NMNH
164580
220086
220094
452449
220089
64.6
52.3
62.7
72.1
44.0
16.1
12.5
15.8
14.8
20.6
4.0 9.5 5.4 31.7
3.5 8.8 5.3 16.7
5.9 11.6 7.5 24.1
4.9 9.9 6.0 25.6
3.3 8.8 4.7 29.2
1.6
1.7
2.1
1.9
2.1
0.50
0.62
0.76
0.41
0.52
Pan
troglodytes
CMNH
CMNH
CMNH
CMNH
CMNH
B3398
B3412
B3413
B3437
B1903
42.0
44.1
37.3
51.4
44.0
18.3
15.1
28.7
13.1
18.6
1.7
2.5
2.7
2.0
2.3
1.2
1.3
1.1
1.2
1.2
0.47
0.38
0.70
0.25
0.67
4.2
6.9
8.1
4.6
6.6
2.4
3.9
5.3
2.8
4.0
28.5
21.4
41.3
22.3
27.5
Papio
ursinus
AZ 784
AZ 45
AZ 193
AZ 44
AZ 769
31.3
48.7
32.7
64.5
64.9
21.3
19.0
20.5
12.8
16.0
3.0 11.1 6.0 26.1 1.5 0.56
3.7 10.6 5.7 26.2 1.8 0.37
2.7 9.3 5.1 26.2 1.5 0.55
3.5 9.3 5.2 17.0 1.2 0.48
6.2 11.7 7.5 28.3 3.3 0.41
Homo
habilis
OH 15
OH 16
OH 4
OH 41
OH 7
Stw 19b
30.8
45.1
44.4
34.6
35.2
46.2
27.6
16.7
28.7
17.7
28.4
25.6
1.8
2.4
3.1
2.0
2.6
2.8
5.2
5.6
9.6
5.8
7.9
6.3
2.8
3.6
5.4
3.7
4.9
4.1
37.6
25.6
43.0
23.9
39.3
40.1
1.3
1.5
1.4
1.1
1.4
1.7
0.44
0.58
0.47
0.67
0.53
0.49
Homo
erectus
KNM-ER 807
KNM-ER 820
KNM-WT15000
OH 60
SK 15
56.2
45.9
47.8
46.6
54.6
14.0
15.0
12.7
20.8
12.8
2.0
2.6
1.9
2.4
2.1
4.6
7.2
4.7
5.5
4.7
2.7
4.0
2.6
3.4
2.8
25.0
21.8
20.1
33.9
22.5
1.2
1.4
1.3
1.5
1.2
0.46
0.54
0.28
0.61
0.49
Sterkfontein
M. 5C
Stw 82
SE 1508
SE 1579
45.9 17.9
17.9 27.1
41.9 18.4
2.7
1.4
2.6
6.9 4.5 27.4 1.3 0.45
4.9 2.8 31.6 1.2 0.51
7.3 4.7 26.0 1.3 0.60
Swartkrans
M. 1
SK 27
SK 45
SK 847
SK 2635
47.2
46.0
53.1
56.7
2.1
2.1
2.4
2.6
5.4
5.2
5.7
5.3
16.8
16.4
14.8
15.2
3.1
3.2
3.4
3.4
26.2
25.2
24.0
27.5
1.2
1.2
1.3
1.5
0.52
0.30
0.48
0.30
* Museums: NMNH Z US National Museum of Natural History;
CMNH Z Cleveland Museum of Natural History; AZ, SK, SE Z Transvaal
Museum, Pretoria; KNM, OH (except OH 7) Z Kenya National Museum, Nairobi; OH 7 Z Tanzania National Museum, Dar-es-Salaam; Stw Z University
of the Witwatersrand, Johannesburg.
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