A University of Calgary archaeologist has found the first prehistoric evidence of chimpanzee technology, adding credence to the theory that some of humanity's behavioural hallmarks were actually inherited by both humans and great apes from a common ancestor.
Dr. Julio Mercader, one of the few archaeologists in the world who studies the material culture of great apes, especially chimpanzees, uncovered stone 'hammers' last year in the Ta rainforest of Africa's Cte D'Ivoire (Ivory Coast) that date back 4,300 years.
Mercader and co-investigators from Germany, UK, the U.S. and Canada report on the findings in the latest edition of PNAS, the Proceedings of the National Academy of Sciences. PNAS is in the top echelon of academic journals internationally.
"It's not clear whether we hominins invented this kind of stone technology, or whether both humans and the great apes inherited it from a common forebear," says Mercader, also a Canada Research Chair in Tropical Archaeology. "There weren't any farmers living in this region 4,300 years ago, so it is unlikely that chimpanzees picked it up by imitating villagers, like some scientists used to claim."
The stone hammers that the team discovered, essentially irregularly shaped rocks about the size of cantaloupes -- with distinctive patterns of wear -- were used to crack the shells of nuts. The research demonstrates conclusively that the artifacts couldn't have been the result of natural erosion or used by humans. The stones are too large for humans to use easily and they also have the starch residue from several nuts known to be staples in the chimpanzee diet, but not the human diet.
Using so-called "percussive technology" to free the edible parts of nuts is more complicated than it sounds. "We know that modern chimpanzee behaviour regarding nut-cracking is socially transmitted and takes up to seven years to learn," Mercader says. "Some of the nuts require a compression force
Contact: Gregory Harris
University of Calgary