Chimps used tools in the Stone Age

Once, thinkers as diverse as Freud, Engels and Thomas Carlyle pointed to the use of tools as a defining characteristic of humans.

Then it was found that many animals also used them, from the "fishing sticks" of apes, to the rocks dropped on ostrich eggs by Egyptian vultures.

And now it has been discovered by Dr Huw Barton, of the University of Leicester, and colleagues in Canada that chimpanzees were using basic "tools" as long ago as the Stone Age.

They report today in the Proceedings of the National Academy of Sciences that stone "hammers" were discovered last year in the Taï rainforest within Ivory Coast, which date back 4,300 years, making the area the only known prehistoric chimpanzee settlement.