November-December 1996
November-December 1996
Roy Larick and Russell L. Ciochon
Emergent Biological Technology
As typified by Homo ergaster, early Homo
was the first hominid to develop a ranging bipedal gait, one that allowed
it to cover a lot of ground in a short period. Long, well-muscled limbs
on a lanky torso also conferred physical strength and defensive presence.
Leverage and strength in the arms and hands gave early Homo the ability
to make simple chopping and cutting implements. Whereas Australopithecus
and Paranthropus had significant sexual dimorphism in body size and
strength, early Homo did not. Among other primates, reduced sexual
dimorphism usually means that both sexes perform similar economic activities,
that males compete less physically among themselves for females and that
males and females pair-bond for long periods. An enlarged cranium also typified
early Homo. A larger brain may have bestowed a more flexible intelligence,
useful for finding resources within new habitats, as well as the complex
behavior Homo came to use against prey and predators.
The early specimens of Homo also exhibit the relatively diminished
premolars and molars-the cheek teeth-of an omnivorous eater, one for which
animal protein played a significant dietary role. As a part-time meat eater,
early Homo probably relied on large carnivores to supply many usable
packages of animal protein-very pragmatically scavenging the remains of
what real carnivores could more effectively hunt. At the other dietary extreme,
these hominids certainly consumed some hard, tough plant foods. In contrast
to Paranthropus, whose digestion of such foods probably began inside
its mouth, early Homo more often and more completely processed difficult
animal and vegetal resources with stone-tool technology, which was employed
to break, crush, split and cut up hard foods before ingesting them. Rather
than being implements of predation, early tools underlay a technology that
essentially added a new first stage to digestion. Indeed, we hypothesize
a close relationship between Pliocene hominid biology and a very elementary
technology, in effect a "biological technology" in which both
the mass and the jagged edges of a few chipped rocks gave early Homo
access to a wide range of nutritional resources. Simple stone tools represent
immediate extensions of the forelimb and hand for breaking down or processing
tough foodstuffs.
Hominid biological remains may be difficult to classify,
but stone tools present even greater problems of interpretation. One way
to understand the development of early stone technology is to envision emergent
and advanced stages separated by a transition. Currently, evidence for the
emergent stage appears with the late-middle Pliocene (about 2.5 mya) in
Hadar, Omo and Turkana. Mzalendo Kibunjia of the National Museums of Kenya
has proposed the name Omo Industrial Complex for such assemblages, in which
rocks were broken or casually chipped into very basic implements. Only a
few general tool types can be defined for the Omo-type assemblages: simple
core choppers and rough flake scrapers. The basic technological characteristics
of Omo-type core-flake assemblages vary by the raw materials available in
each region. In Hadar and Turkana, where large volcanic cobbles are present,
the tools tend to be large and the chipping technique a little more complex.
In Omo, where small, tough quartz cobbles were used, the tools are much
smaller and more haphazardly made. At present, the Omo-type localities and
tools represent the initial threshold of stone technology at a date that
correlates well with the emergence of Homo itself.
The advanced or Acheulian stage begins with the early Pleistocene, about
1.6 to 1.4 mya-well after Homo ergaster attains full development
in the Turkana Basin. The Acheulian technological complex is achieved as
the selection of raw materials, the preparation of the stone core and the
chipping procedures become much more complex, and the tools themselves become
somewhat specialized. Bifacial chipping is the hallmark of the Acheulian
Industry. With this technique, a tool blank is chipped from two directions
across a bisecting plane. The blank is worked around a circumferential edge
to resemble a plump discus, or a double-sided tortoise shell, and the entire
edge becomes the working part. Although earlier hominids had developed crude
bifacial techniques by 2.0 mya, the method did not become the basis for
a distinctive set of Acheulian biface tools until about 1.5 mya. The Acheulian
appears to emerge in the eastern Rift in areas such as Konso-Gardula in
Ethiopia, as well as Peninj and Olduvai Gorge in Tanzania. Nevertheless,
Acheulian bifaces are found as far north as the Jordan Valley of Israel
(at 'Ubeidiya) by 1.4 mya. When hominid remains and early Acheulian tools
are associated within any site stratum in Africa, the species is always
Homo ergaster or Homo erectus, not Homo habilis or
Paranthropus boisei.
The period from about 2.0 to 1.5 mya is best seen as a long and important
transition between the advent of chipping techniques and the achievement
of standardized Acheulian biface tools. Much of this period is represented
in the lower beds of Olduvai Gorge, Tanzania, where Mary Leakey of the National
Museums of Kenya defined the well-known Oldowan Industry more than 30 years
ago. At the time, the Oldowan was thought to be the earliest manifestation
of stone technology and, indeed, the earliest assemblages in Bed I (the
oldest levels of Olduvai) resemble those from Ethiopia and northern Kenya
now deemed oldest. Nevertheless, most Oldowan tool kits reflect more care
and skill in choosing raw materials and in preparing and striking cores
to create usable flakes and core tools than do the Omo-type assemblages.
Over the several hundred thousand years evident in Olduvai's stratigraphy,
Oldowan assemblages undergo distinct refinement in chipping techniques and
some standardization in tool form. By 1.7 to 1.6 mya, bifacial tools help
to define the Developed Oldowan Industry. At Olduvai, the initial stone
tool finds came in stratigraphic association with a new hominid, one with
a larger brain and more gracile features than had the previous robust australopith
skull found at Olduvai Gorge (Paranthropus boisei). The clear association
of an advanced hominid with stone tools prompted the Leakeys to designate
the new species Homo habilis, literally "handy man." It
becomes clear that more than one species of Homo--and probably Paranthropus
boisei--made Oldowan-type tools at Olduvai Gorge and elsewhere.
Given its relatively early appearance and greater complexity over the earlier
stages as well as its association with Homo ergaster, the African
Acheulian technology has often played into hypotheses for Eurasian dispersal.
However, new dates and technological analyses make any such role unlikely
in Asia. Although Acheulian tools always seemed to antedate the earliest
tool assemblages in East Asia, the recently discovered stone tools at Longgupo
and Riwat are as ancient and as simple in design as their Omo and early
Oldowan counterparts in Africa. None of the older Asian assemblages contain
handaxes, and few exhibit even the standardized chipping patterns of the
Developed Oldowan or the Acheulian technologies.
The current and revolutionary evidence for a very early dispersal of hominids
from Africa to Asia may be reiterated as follows. 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. The emergence of Acheulian technology in east Africa confirms the
hypothesis for early Asian dispersal. Distinctive bifaces date to 1.5 mya
in the eastern Rift Valley and the Middle East, and to 600,000 years ago
in Europe. The absence of Acheulian bifaces at the early sites in south
or East Asia suggest that Homo must have initially left Africa before
the Acheulian stage appeared in Africa. Consequently, early Homo
dispersed to subtropical Asia with a very elementary technology.
© American Scientist 1996