As anyone with a weakness for pistachios knows, eating nuts can be a lot of work, but the rewards are worth the effort. The high-fat, high-protein foods are also a favorite of humans' closest living relatives, chimpanzees. In the tropical forests of West Africa, chimpanzees use stone or wooden hammers to break open tough nut shells. That behavior now may shed light on how early hominids began to make and use tools.
In the 24 May issue of Science , primatologist Melissa Panger and archaeologist Julio Mercader, both of George Washington University in Washington, D.C., with primatologist Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, present one of the first research reports on chimpanzee archaeology--a description of stone pieces they dug up at a chimp nutcracking site in the Taï forest in Côte d'Ivoire.
The team identified six wooden anvils around a recently deceased Panda tree where chimpanzees had cracked nuts. They also found a wealth of stone pieces, evidently broken off as the chimpanzees pounded their hammers on the nuts. Some pieces, the team claims, resemble some of those found at certain early human sites. The researchers argue that the chimps' leavings bear some resemblance to some of the simplest artifacts left by hominids millions of years ago. Mercader says the chimp assemblage raises the possibility that scientists could identify sites where ancient hominids, like the chimps, used unmodified stones as tools--something that so far hasn't been spotted in the archaeological record. It may also deepen understanding of ape behavior: By comparing the modern pieces to older pieces they hope to find, the researcher hope to trace the history of tool use in apes.
Sophisticated tools appear suddenly in the human archaeological record about 2.5 million years ago and additional study of chimp sites might help researchers detect ancient assemblages that represent earlier steps in toolmaking, says Stanley Ambrose of the University of Illinois, Urbana-Champaign. "It is a short step from accidentally producing sharp-edged flakes and blocks to discovering their utility for cutting and chopping." But even the "simplest" ancient hominid sites are "fundamentally different" from those of chimpanzees, cautions paleoanthropologist Tim White of the University of California, Berkeley.