Aping the Stone Age: Chimp Chasers Join Artifact Extractors to Probe the Roots of Stone Tools
Bower, Bruce, Science News
For chimpanzees living in a forest surrounding the village of Bossou in Guinea, cracking nuts is a serious task with important steps. They are: First, lug large rocks to a spot near a nut-bearing tree, such as an oil palm. Next, gather the nuts and place them on the rocks. Then, obtain a smaller, graspable rock. Finally, smash the armored treats and let the shells fly. As clutches of apes pound away with devastating precision, these nut bashers create an unholy din akin to a human rock band.
In fact, these West African chimps rock out in a surprising way. In this corner of the jungle, chimps appear to think more carefully about implements and how to assemble them than many scientists had assumed. A team led by anthropologist Susana Carvalho set up a nut-cracking lab in the forest near Bossou by placing seven piles of nuts and several dozen stones of various sizes, shapes and types inside a clearing. Over five field seasons, 14 of 17 chimps that regularly visited the clearing consistently reused the same pairs of stones, the scientists report in a special October issue of Animal Cognition. Most chimps, Carvalho says, used the stones together as one tool, a nutcracker.
Carvalho suspects that watching the Bossou chimps at work will provide clues to the origins of the Stone Age, the 2.6 million years during which members of the human evolutionary family are known to have used and made stone tools of increasing complexity. She is one researcher participating in a scientific movement to merge strains of archaeology, anthropology, primatology and psychology into a hybrid field dubbed primate archaeology: the study of current and past material culture among apes and perhaps other nonhuman animals.
"Very few archaeologists and paleoanthropologists have seen a wild ape, and very few primatologists have done any excavation or analysis of artifacts and fossils," says Cambridge primatologist William McGrew, who has studied wild chimps for more than 40 years. "We have much to offer one another."
If, for example, the modern chimps' pounding leaves signature damage on the stones, then sites holding remains from ancient African hominids--now-extinct members of the human evolutionary family--could be probed for similarly marked stones. Such markings could reveal tools that may have preceded the earliest known stone tools, known collectively as the Oldowan industry, named for Olduvai Gorge in Tanzania. These single-edged cutting implements date from around 2.6 million years ago. Researchers could also search the modern chimps' nut-cracking site for sharp stone fragments produced during pounding. Such accidentally sharpened fragments may have stimulated the invention of Oldowan tools.
Early hominids possessed chimp-sized brains and some other chimplike traits, making living chimps a reasonable group to compare with hominids, Carvalho contends. (That view is controversial; SN: 10/24/09, p. 9).
Carvalho, a graduate student at the University of Cambridge in England, and 17 other scientists set out the case for primate archaeology in the July 16 Nature. New investigations inspired by this perspective are set to appear in an upcoming Journal of Human Evolution.
For now, primate archaeology focuses on chimps, though gorillas and orangutans, capuchins (SN: 2/14/09, p. 12), crows (SAT: 8/29/09, p. 5), dolphins (SN: 1/3/09, p. 13) and other animals also make and use tools. One line of research explores how cultural traditions in tool use and other behaviors spread among African chimp communities, with possible implications for understanding cultural links among ancient hominid groups. Another project combines chimp, hominid and modern human data to explore the mystery of why most people are right-handed. And new finds in Africa reveal the possibility of a chimp stone age.
Chips off the old block
Primatologist Andrew Whiten of the University of St. …