Chimp Stoned Tools

Culture vs. Nature in Broken Rocks

This week, a paper was published in the Proceedings of the National Academy of Science Early Edition by a research team led by Julio Mercader of the University of Calgary about three archaeological sites in Ivory Coast, Africa which appeared to represent nut-cracking stations created by chimpanzees about 4,300 years ago. Basically the chimps had been using rocks to bang on nutshells, and the researchers determined it was chimps rather than humans, (1) because the rocks weren't modified other than being used to bang on the nuts, (2) because the rocks that were used to bang on the nuts were too large to have been comfortably used by humans, and (3) because starch grains identified on the edges of the rocks included four species of nuts not considered edible by humans.

No archaeologist is really surprised about this--nut cracking was reported last year in Cameroon, and tool use by chimps has been known since the mid-19th century, as any kid who has sat through an introductory anthropology course can tell you all about chimps using sticks to poke at ant nests. I started an article on this new finding, but kept getting distracted by several questions that needed to be fleshed out. Also, I was deeply disappointed that I couldn't write about "chimp stoned tools", which is funny if you're an archaeologist and lame if you're not. And as a matter of fact is pretty lame anyway.

One of the questions I realized hadn't been answered is--how do archaeologists tell when a heap of broken stones has been made by humans as opposed to broken by nature? Archaeologists make this determination all the time, but I don't think it's in the general public mind, at least I couldn't find a good description on the Internet anywhere. So, here you go. A couple of detailed articles on the characteristics of a heap of broken rock that archaeologists use to determine whether an artifact is a geofact (made by natural forces) or from systematic flaking (made by humans).

• Geofacts: When is a Broken Rock Not an Artifact?
• Systematic Flaking: What Identifies Broken Rocks as Man-Made?

For people interested in more on the chimp story, here's a collection of the latest stories from other folks who have actually written about the actual story, as opposed to just vamping on the refrain.

Chimp Links

Mercader, Julio, Huw Barton, Jason Gillespie, Jack Harris, Steven Kuhn, Robert Tyler, and Christophe Boesch. 2007. 4,300-year-old chimpanzee sites and the origins of percussive stone technology. Proceedings of the National Academy of Sciences, although it doesn't seem to be available online right now.

Morgan et al. 2006. "Chimpanzees use stone hammers in Cameroon." Current Biology 16 (16): R632-3.

Wrangham, Richard. 2006. Chimpanzees: The Culture-Zone Concept Becomes Untidy. Current Biology 16:R634-R635.

Blog Commentary

• Chimpanzee Archaeology - stone tools used by chimps from 4,300 years ago, Kambiz Kamrani on AnthroNet
• Chimpanzee archaeology, by John Hawks

News Stories

• Dating chimp "Stone Age", Bryn Nelson at Newsday
• Archaeologists Find Signs of Early Chimps’ Tool Use, John Noble Wilford in the NYT
• Ancient hammers made by chimpanzees fuel debate over evolution, Bill Graveland in the Canadian Press
• The Chimpanzee Stone Age, Ann Gibbons in Science Now.
• chmpanees may have their own Stone Age: study, Reuters