Reflections on the Origins of
Scavenging and Hunting in Early Hominids.
When did our earliest human ancestors first begin to scavenge for meat
and first begin to hunt? This is a difficult question to answer with
certainty. We cannot ask them, and their few surviving fossils offer
clues that are at best inferences. The question must be approached using
very limited data. Nonetheless, by using several approaches to the question,
a very plausible answer seems within grasp. I hypothesize that both
scavenging and hunting coincided with the emergence of the genus Homo.
I will first discuss the several areas of evidence that have entered
into this inquiry. Thereafter I will discuss the species of hominids
in relation to the evidence.
Fossils, though few and rare, are by far the most important evidence
we have of hominid evolution. Fossils and paleoarchaeological excavations
have provided both anatomical evidence and indications of behaviors. In
addition to the scant evidence offered by fossils, an understanding of
evolution and its relationship to paleoecology and climate changes offers
useful clues and some possible answers. Paleoclimate studies evidence
the temporal alterations in the forces that have influenced hominid evolution.
Evolution takes place in a context, and a holistic understanding of
fossil evidence requires a look at that context. Let us begin by placing
the fossils in their hypothetical environment. Primates evolved in tropical
and subtropical climates as plant eaters. Primates differentiated into
several species of apes around 15 mya (million years ago). Around 12
mya the climate became drier and parts of the African tropical forest
niche was replaced by grasslands. Tectonic changes also affect climate.
These changes have been summarized by Brunetto Chiarelli as follows:
"In the last 12 million years sub-Saharan Africa underwent climatic
changes because of the tectonic movements which created the Rift Valley.
The climate became drier and the forests were replaced by bushveld
and savannas. In eastern regions especially, some apes had to learn
to live in a new environment: open plains where a specialized cleverness
was necessary to survive. About 6-5 million years ago they began to
evolve into Australopithecus, with erect posture and a higher encephalic
quotient. Climate change was at the origin of this development." (Chiarelli,
The fossil record evidences branches of the primate tree that failed
to adapt to environmental and ecological change and perished. Approximately
16 mya, during a warm climate epoch, Pliopithecus and Dryopithecus,
two genera of primates, migrated from Africa into Eurasia. These species
are particularly illustrative to the present discussion because they
were vegetarians, and therefore not preadapted to an ecology with fewer
plants and a cold season. They became extinct due to the climate cooling
about 14 mya, except in tropical Southern Asia where they evolved into
Orangutans (Pickford, 1968).
During the warmer period in Eurasia and in the forests of tropical
and subtropical Africa there was no reason to switch to meat. More than
100 food plant species suitable for primates are available in the equatorial
forest. This prolific ecology, which was originally spread across the
entire African equatorial belt, was greatly reduced in the east by the
sinking of the Rift Valley. There also the hominids had to adapt to
a landscape with reduced vegetation or perish (Pickford, 1990). The
survival pressures may not have been as extreme as at more northerly
latitudes. In this scenario, in Africa around 5 mya ago, Australopithecus
equipped with new survival tools, bipedalism and a slightly larger brain,
evolved. These preadaptive features may have ensured their survival
and our evolution during a cooling event in the Late Miocene epoch (about
6.0-5.3 mya). This correlates well with the time at which apes and hominids
diverged (Larick and Ciochon).
Increased brain size had occurred several previous times in our evolution.
Those events support the hypothesis that changes in the environment
and ecology, and their consequent pressures, can select for greater
brain size. Approximately 220 mya, at the beginning of the evolution
of mammals, a major encephalization occurred. A second major encephalization
occurred following the Mesozoic extinction 65 mya, when a dramatic change
of the niches of mammals took place. "In mammalian and primate history,
one of the major responses to changes in environment was the enlargement
of the brain in relation to body size," according to Brunetto Chiarelli.
Given this correlation, a significant increase in brain size can also
infer an epoch of changes and new adaptations. The size of the hominid
brain has increased from about 500 cc. to 1500 cc. during the last 2
to 3 million years, the largest quantitative evolutionary change in
the history of the mammals (Chiarelli, 1996). This vast change can be
viewed as a temporal graph of adaptive history. Pinpointing when the
greatest changes occurred can illustrate periods of new adaptations
and extreme survival pressure.
Another area of evidence that merits attention is behavioral ecology.
With fossil species, the difficulty arises in trying to find evidence
of behaviors. Studying an animal in relation to its environment involves
understanding the quantity and quality of different kinds of food, distribution
of food resources and water, predators and group size. Groups can form
in response to predation. Behavior, to be an inherited trait, must have
an impact on reproductive success, such as living in groups increasing
predator detection (Paxton). In primates much observed behavior is a result
of learning rather than genetic, and is passed from generation to generation
as part of culture. Tool use is such an acquired behavior. An example
is termite extracting with sticks by chimpanzees. Learned behaviors can
also impact reproductive success and evolution.
Fossils offer some evidence of behaviors. Teeth can be viewed microscopically
to discover the kinds of foods chewed. The microscopic scratches and pits
that form on a tooth's surface as the result of chewing are useful evidence.
Heavily pitted molar surfaces typically suggest a diet consisting of harder
food items (such as hard seeds, nuts or bone). In contrast, a heavily
scratched shearing facet on a molar tooth usually indicates that the tooth
was used to shear food items (such as leaves or meat). Intermediate patterns
indicate mixed diets.
Dietary differences are revealed by comparison of microwear images
of two fossil apes from the late Miocene of Europe, Ouranopithecus
and Oreopithecus: The heavily pitted surface on the molars of
Ouranopithecus macedoniensis suggests the consumption of harder
food items such as nuts or tubers. The heavily scratched surface on
the molars of Oreopithecus bambolii suggests a diet comprised
of leaves or other soft objects.
Tools are also valuable evidence of behaviors. Tools have been encountered
in association with fossils. And because the earliest hominid tools
are associated with scavenging, they are our most valuable behavioral
evidence in relation to carnivorous activity. The first hominid tools
provided a technology that added a first stage to digestion, preprocessing
foods and giving early hominids access to a wider range of nutritional
resources, imparting a survival advantage. Stone tools are extensions
of the forelimb and hand for breaking down or processing tough foodstuffs
(Larick and Ciochon).
Current evidence for the emergent stage of tool making appears about
2.5 mya in Hadar, Omo and Turkana with simple core choppers and rough
flake scrapers. This initial threshold of stone technology correlates
well with the emergence of Homo itself. Recently Larick and Ciochon
"Fragmentary fossils representing the emergent genus Homo
are consistently dated to nearly 2.5 mya at various points in the
eastern Rift Valley. Likewise, as the earliest stone tools, also found
in the eastern Rift, have equal antiquity, the emergence of one must
be linked to the other. By 1.9 mya, Homo ergaster presents
undeniable morphological features for moving great distances: long
torso and limbs, narrow hips, a large brain and reduced dentition.
With the new evidence from Longgupo, Java and Riwat, it becomes clear
that early Homo (the immediate ancestor to Homo ergaster
and Homo erectus) and simple stone tools arrived in tropical
and subtropical Asia by about 2.0 mya."
Genus Homo had crude bifacial tools by 2.0 mya. These became
the distinctive Acheulian biface tools about 1.5 mya in the eastern
Rift in Ethiopia, and in Peninj and Olduvai Gorge in Tanzania. Acheulian
bifaces are found in Israel by 1.4 mya. Early Acheulian tools are associated
with H. ergaster or H. erectus (Larick and Ciochon).
What enabled the early migration out of Africa? It certainly was not
the diet of 100 plants in tropical forests. Two sequential patterns of
subsistence behavior are evidenced in the tool and fossil record. The
first, at the earliest stone tool sites about 2.5 mya, occurs near natural
features termed "catchments" to denote the presence of numerous complementary
resources. Here large, diverse accumulations of bone and stone waste indicate
significant occupation. After exhausting one catchment's resources, the
group would presumably move to another. Larick and Ciochon term this "catchment
scavenging." This pattern was followed by a more territorial approach.
It is the first adaptation that temporally corresponds to the dispersal
of hominids out of Africa. The capability to migrate across vast distances
and into new ecological niches with different plants is indirect evidence
that the emergent Homo species was relying on meat to survive.
The coincidence of climate change, emergence of the earliest Homo,
the appearance of stone tools, and species dispersal provide rather convincing
evidence of meat scavenging by this point in hominid history.
New adaptations and behaviors should correspond to increased brain size.
As we have already observed, selective pressures were responsible for
the increase of the brain size at earlier points in our evolution. During
the evolution of Australopithecines into Homo habilis and H.
erectus brain size more than doubled. This supports the other evidence
of new adaptations.
Let us move on to an examination of what we know about the individual
fossil hominid species, with attention to the factors in the foregoing
We know that monkeys and apes are plant eaters. Australopithecines also
lived on plant food. Tooth wear evidences a diet of leaves and fruits
(Grine and Kay, 1988), and probably also tubers, seeds and insects (Isaak,
1978; Parker and Gibson, 1979). According to Meave Leakey and Alan Walker,
"our evidence suggests that the earliest bipedal hominid known to date
lived at least part of the time in wooded areas." Fossils buried near
Ardipithecus ramidus, such as seeds and the bones of forest monkeys,
imply that they lived in a closed-canopy woodland. Fossil evidence also
supports the view that early hominids occasionally inhabited a riparian
habitat. This data supports the view that Australopithecenes were primarily
Australopithecus anamensis existed between 4.2 and 3.9 mya, and
has a mixture of primitive and advanced features. The teeth and jaws of
anamensis are primitive, similar to older fossil apes (Foley).
At Kanapoi workers recovered two nearly complete lower jaws, one complete
upper jaw and lower face, and several sets of isolated teeth. The thickened
enamel suggests that A. anamensis had already adapted to a changed
dietpossibly much harder food (Leakey, and Walker).
Australopithecus afarensis existed between 3.9 and 3.0 mya, had
a protruding jaw with large back teeth, and had more human-like teeth
than that of a chimpanzee. The canine teeth are smaller than modern apes,
but larger than those of humans, and the shape of the jaw is intermediate.
Australopithecus africanus existed between 3 and 2 mya. It is
similar to A. afarensis. Brain size was a little larger than chimpanzee
brains. The teeth and jaws are much larger than those of humans, yet more
similar to human teeth than to those of apes (Johanson and Edey 1981).
The jaw shape is fully parabolic and canine size is reduced compared to
A. afarensis. "Fossils of afarensis include various bone
and joint structures typical of tree climbers," according to Meave Leakey
and Alan Walker.
Donald Johanson infers that A. africanus was vegetarian, "In
my opinion, A. africanus, with its heavily buttressed mandible
and expanded chewing teeth, forecasts the vegetarian specialization
of the robust forms."
Australopithecus aethiopicus existed between 2.6 and 2.3 mya.
This species may be the ancestor of A. robustus and A. boisei.
The brain size is 410 cc. The massiveness of the face, jaws and single
tooth found, and the largest sagittal crest in any known hominid, are
noteworthy. The Black Skull (A. aethiopicus), at 2.5 million
years, is intermediate between A. afarensis and the later
A. robustus and A. boisei.
Australopithecus robustus existed between 2 and 1.5 mya. It
had larger and more robust skull and teeth than A. africanus,
with small front teeth and massive molars set in a large jaw. They had
a brain size of about 530 cc with sagittal crests, evidence of large
chewing muscles. This increase in brain size may be a reflection of
overall size, not a significant evolutionary modification. Diet was
probably coarse, tough food that needed a lot of chewing. Bones excavated
with robustus skeletons may have been used as digging tools, also a
vegetarian adaptation (Foley).
The robust australopithecines with their massive jaws, greatly enlarged
chewing muscles, and huge crushing and grinding molar teeth were specialized
to process tough, fibrous, vegetarian diets (Johanson). Johanson wrote,
"The vegetarian specialization of our robust relatives was a continuation
of a longstanding dietary adaptation and feeding strategy among hundreds
of species of primates." The robust hominids and their ancestors seem
unlikely to have been meat scavengers, at least not in a significant way.
Their brain sizes do not reflect a significant change from their predecessors,
and therefore I conclude, based on all the factors discussed above, that
they did not make very significant new adaptations to their environment
at the time that genus Homo emerged. This may be why australopithecines
are all extinct today.
The robust australopithecines probably coexisted with hominid scavengers.
About 3.0 to 2.4 mya, the Middle Pliocene cooling produced a relatively
cool, dry climate in tropical Africa, further altering the ecology.
At about this time, between 2.5 and 2.0 mya, the earliest species of
the genus Homo emerged, (Larick and Ciochonto). The first Homo
seems to have exploited the new habitats as an aggressive scavenger.
This aggressiveness is suggested by the fact that its African emergence
and Asian dispersal are temporally proximate. The adaptations which
led to Homo evolving from Australopithecus may also have
enabled early Homo to migrate far from the tropical forests of
equatorial Africa. The addition of animal protein to their diet would
have been useful, if not necessary, for survival in the cooler, more
temperate climates and more northerly latitudes, especially when plant
food is less available in the winter season. Larick and Ciochon recently
"We reconsider the new evidence for early dispersals in the light
of climatic, morphological, technological and behavioral factors hypothesized
for the emergence of Homo. We find that the striding gait,
the elementary stone tools and the simple, but expansive, pattern
of scavenging that characterizes the emergence of Homo also
served its initial dispersal."
A 1.8-million-year-old early Homo tooth fragment has been reported
from Orce in southern Spain. A jaw bone of similar age was found in
the Republic of Georgia. In Indonesia specimens of Homo erectus
date to 1.6 to 1.8 million years. The success of the Homo diaspora
evidences a successful new adaptation, and tool use was an important
aspect of this adaptation. Stone tools in Pakistan have a paleomagnetic
age of about 1.9 million years. The 1.9 my old Longgupo hominid, found
in China, has teeth with affinities to early African Homo and
possessed similar stone tools (Larick and Ciochon). This hominid is
possibly more primitive than H. erectus (Beardsley). According
to Larick and Ciochon, "The growing number of Asian hominid fossils
and stone-tool assemblages that approach 2.0 million years in age now
suggests that an early population of Homo arrived in eastern
Asia within a few hundred thousand years of arising in Africa."
Were the earliest tools used for scavenging only? Could scavenging
alone have supported this rapid diaspora? Other mammalian species were
also affected by Africa's changing ecology. Six species of African bovids
dispersed to Asia during the Middle Pliocene, a surprising number. These
bovids could have been hunted or scavenged by Homo and the two groups
may have dispersed at the same time (Larick and Ciochon). Could pursuit
by Homo hunters have been a factor in their dispersal? Was 'Homo
the traveler' also a hunter capable of giving chase to an obvious huge
banquet? By 1.9 mya Homo ergaster exhibited limb proportion and
body size comparable to Homo sapiens and a cranium larger than
that of Homo habilis (Larick and Ciochon). I suspect that the
capability existed, and was used.
Homo habilis existed between 2.4 and 1.5 million years ago. Evidence
of tools found with habilis earned it the name, which means 'toolmaker.'
H. habilis is similar to australopithecines but the back teeth
are smaller, though still relatively large. Brain size, at between 500
and 800 cc, is considerably larger than in australopithecines and brain
shape is more human like. One feature, the bulge of Broca's area visible
in one habilis brain cast, suggests a possible capability of rudimentary
speech (Foley). Organized social groups and vocal cues are adaptive to
hunts. Early language could have capacitated successful group hunting.
It is easier, therefore, to make a case for H. habilis being a
hunter. Nonetheless, I view the ability to migrate over several continents
to be more significant evidence of adaptation to meat eating and possible
hunting than evidence of possible increase in vocal capability. Language
has many uses besides hunting.
Ten sites at Oldavai that date from the Homo habilis period contain
Oldowan core and flake tools and animal bones (Feder and Park). Analysis
of the bones from these sites indicated that they were mostly antelope
lower legs, parts with little or no meat. The bones also show tool marks,
sometimes overlying carnivore tooth marks, sometimes the opposite. Oldowan
tools were definitely used for cutting meat. Because a greater proportion
of the bones than expected represent animal parts with little meat, they
appear to have been scavenged for marrow, not hunted.
Was Homo habilis a scavenger, while the Homo that
dispersed a hunter? All the Australopithecines and Homo habilis
are only found in Africa. Early Homo and H. erectus were found
through Africa and Asia. H. erectus existed between 1.8 million
and 300,000 years ago. Their stone tools are more sophisticated than habilis'
tools (Foley). Their average brain size was 900 cc in early specimens
and about 1100 cc later (Foley). These differences also suggest a difference
in adaptation. This change may have included hunting. While the limited
evidence suggests that H. habilis may have only scavenged, hunting
is not so different than scavenging.
Once a taste for meat developed, hunting may have been only a thought
away. Certainly, the earliest meat scavengers had the intelligence to
understand where the meat derived fromliving animals. The simplest
form of hunting, a chase, does not require stone tools which would be
evidenced today. The pressures of existence and survival may have been
greater the further early Homo moved from its tropical homeland,
and therefore the likelier the possibility of hunting.
In conclusion, the available evidence indicates that the emergent Homo
species made a significant new adaptation to the environment in East Africa
during the Middle Pliocene cooling. Unlike their robust Australopithecine
cousins, they scavenged meat. And they used stone tools to do so. Scavenging
and hunting capacitated survival in ecologies without the ancestral plants
of the African tropics. H. habilis was certainly a scavenger, and
possibly a hunter. Eating meat enabled a significant dispersal in more
northerly latitudes and into new ecological niches. In all probability
the earliest Homo to disperse from Africa was a hunter as well
as a scavenger. This view provides the dispersing early Homo with
a capability to explain its rapid diaspora and regional successes.
Whoever that first individual hominid that taught his fellows to eat
meat was, she/he certainly altered the course of history. Without that
behavioral innovation, however repulsive it may have seemed to those
ancient vegetarians, and without its cultural transmission, the species
Homo sapiens may never have come into existence. We have to thank
that ancient ancestor for our very existence, for the emergence of our
genus. At the same time we should reflect on the number of species that
may have fallen into extinction due to our omnivorous appetites and
species success. In a sense this question is the story of the six billionth
monkey! Or rather, hominid.
Beardsley, Tim, Out of Food? http://www.sciam.com/0496issue/0496scicit01.html.
Chiarelli, Brunetto, Some comments on the evolution of hominid intelligence.,
Mankind Quarterly, Fall, 1996, Vol. 37 Issue 1, page 29-37.
Chiarelli, Brunetto, The `African Eve' theory in light of paleontological
evidence for the outward diffusion of hominids., Mankind Quarterly,
Spring 1994, Vol. 34:3.
Feder, Kenneth L., and Michael Alan Park, Human Antiquity, Mayfield
Publishing Company, Mountainview, CA, 1997.
Foley, Jim, Fossil Hominids FAQ, talk.origins Archive, April
Grine, F. E., Kay, R. F., 1988, Early hominid diets from quantitative
image analysis of dental microwear. Nature 333: 76S-768, cited in
Isaac, G., The food-sharing behavior of Protohuman Hominoids.
Scientific American 238:4. pages 90-108, 1978, cited in Chiarelli, 1996.
Johanson, Donald C., A skull to chew on., Natural History, May
1993, Vol. 102 Issue 5, p. 52.
Larick, Roy and Russell L. Ciochon, The African Emergence and Early
Asian Dispersals of the Genus Homo, Nov. 1996, http://www.sigmaxi.org/amsci/articles/96articles/Larick.html.
Leakey, Meave; Walker, Alan, Early hominid fossils from Africa.,
Scientific American, June 1997, Vol. 276, Issue 6, p74.
Parker, S. T., K. R. Gibson, A developmental model for the evolution
of language and intelligence in early hominids. Brain Sciences,
2:367-408, 1979, cited in Chiarelli, 1996.
Paxton, Steve and Terry McAndrew, Primate Behavior, http://www.leeds.ac.uk/chb/lectures/anthl_11.html.
Pickford, M., Major events in primate paleontology; possible support
for climatic forcing models of evolution., Antropologia Contemporanea,
9: 89-94, 1986, cited in Chiarelli, 1996.