145;Stone Age146; Chimps

Archaeological findings suggest primates had inherited the know-how of nut-cracking tools 4,300 years ago

Chimpanzees were using stone tools to crack open nuts at least 4,300 years ago, according to new evidence that poses tantalising questions about the origins of tool use in primates.

The discovery of the nut residue-embedded stones in a Cote d8217;Ivoire rainforest, the study authors say, raises the possibility that tool know-how from this Chimpanzee Stone Age was inherited from the ancient common ancestor of both chimps and humans.

8220;This discovery speaks of true prehistoric great ape behavior that predates the onset of agriculture in this part of Africa,8221; the study asserts, arguing that chimpanzees didn8217;t simply mimic local farmers.

8220;For me, the exciting thing is that we are looking at finding what 8216;humanity8217; really means and identifying that in the distant past,8221; said Julio Mercader, a study co-author and Canada Research Chair in Tropical Forest Archaeology at the University of Calgary in Alberta.

For the study, which will be published on Tuesday in the Proceedings of the National Academy of Sciences, Mercader and his colleagues focused on three archaeological sites on a riverbank within the Tai National Park. Carbon-based dating techniques estimated an age of about 4,300 years for the mostly granite and quartz stones, many showing signs of wear and breakage.

The surrounding sediment patterns intimated that the stones were not deposited by water but instead deliberately left at the sites. But by whom?

Some stones had been subjected to systematic flaking, implying that human tool users sporadically visited the riverbank. The features of many other stones, however, suggested they were used like hammers by the stronger chimpanzees, whose longer palms would have been able to wield larger tools. Both the wear patterns and stone selection resembled that of modern chimps inhabiting the same forest.

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Mercader said the 8220;smoking gun,8221; though, arrived through an analysis of starch embedded in some stones. Chimpanzees currently living in the Tai region are known to crack open five types of nut, four of which are not used by local humans. A microscope-aided analysis suggested that at least three-fourths of the starch granules on the stones came from nuts and that a significant fraction were from those nut varieties used only by chimps.

The prehistoric chimpanzee site, the study authors conclude, suggests that nut-cracking behaviour in the forest has been passed down from chimp to chimp over the course of more than 200 generations.