Week of March 30,
2002; Vol. 161, No. 13
Archaeologists, by definition, uncover the remnants of past human activity.
With the first excavation of chimpanzee stone tools at an African site,
however, the scope of their work has entered virgin terrain.
Chimps transported suitable pieces of stone to the undated site and used
them to crack open nuts placed on thick tree roots, according to Julio
Mercader of George Washington University in Washington, D.C. "At
least some wild chimpanzees have produced stone [artifacts] and left behind
an archaeological record of their nut-cracking behavior," says Mercader,
who directed the excavation. He described the recent discoveries at the
annual meeting of the Paleoanthropology Society, held last week in Denver.
Researchers previously had reported that chimps living in western Africa's
Taï forest avidly stockpile stones at places with broad tree roots
or stumps that serve as anvils for cracking nuts. This activity may represent
a learned behavior peculiar to the local animals, since chimps living
in other parts of Africa don't use stone implements (SN: 6/19/99, p. 388).
Mercader and his coworkers excavated a Taï forest site called Panda
100. Trees bearing so-called Panda nuts grew in this region until 1996,
when they died out. The chimp artifacts haven't been dated yet.
The researchers chose their dig site after noticing four large tree roots
that displayed pounding marks made by stones. Excavation of trenches at
the site yielded two more tree roots with similar
markings. Fragments of nutshells were recovered around all six roots.
Moreover, Mercader's group unearthed 479 stone artifacts, often in close
proximity to the shell fragments. These artifacts included the remains
of hammering stones, thin flakes that had been pounded off
those stones, and pieces of shattered rock.
The earliest known stone tools, made by human ancestors in eastern Africa
around 2.6 million years ago, consisted of sharpened chopping implements
and larger rocks used as anvils. Chimps' hammering stones recovered at
Panda 100 are about the same size as those ancient choppers, Mercader
says. However, implements used by human ancestors show more evidence of
having been intentionally modified than do those attributed to chimps,
The Taï forest discoveries suggest that archaeologists may be able
to investigate links between nut-cracking tools employed by chimps and
human ancestors, says wild-chimp researcher William McGrew of Miami University
in Oxford, Ohio. Homo species cracked nuts with stone implements at least
780,000 years ago (SN: 2/23/02, p. 117)
"There seems to be a signature of chimpanzee archaeology at Panda
100, which is pretty cool," remarks Nicholas Toth of Indiana University
in Bloomington, who studies ancient stone tools. Still, he adds, "the
Taï forest material that I've seen looks fairly crude."
In contrast, human ancestors' earliest known tools exhibit remarkably
sophisticated workmanship, Toth says. In a study presented at the Paleoanthropology
Society meeting, he and his coworkers discerned that 2.6-million-year-old
stone tools and present-day stone chopping implements fashioned by experienced
tool makers required similar skills.
Toth also notes that two captive bonobos, or pygmy chimpanzees, have learned
to make chopping tools out of rocks with considerable proficiency, though
not up to human skills. Chimps' tool-making disadvantage largely derives
from having large hands that can't manipulate objects as well or generate
as much striking force as human hands can, Toth says.
References and Sources
Mercader, J., M. Panger, and C. Boesch. 2002. Chimpanzee-produced stone
assemblages from the tropical forests of Taï, Côte d'Ivoire.
Paleoanthropology Society Meetings. March 19. Denver
Toth, N., K. Schick, and S. Semaw. 2002. A technological comparison of
the stone tool-making capabilities of Australopithecus/early Homo, Pan
paniscus, and Homo sapiens, and possible evolutionary implications. Paleoanthropology
Society Meetings. March 19. Denver.
Bower, B. 2002. Almond Joy, Stone Age Style: Our ancestors had a bash
eating wild nuts. Science News 161(Feb. 23):117.
______. 1999. Chimps employ culture to branch out. Science News
Department of Anthropology
George Washington University
Washington, DC 20052
Center for Research into the Anthropological Foundations of
419 North Indiana
Bloomington, IN 47408
From Science News, Vol. 161, No. 13, March 30, 2002, p. 195.
Copyright (c) 2002 Science Service. All rights reserved.
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