WASHINGTON — Chimpanzees may have been using stone ‘hammers’ as long as 4300 years ago. An international research team led by archeologist Julio Mercader of the University of Calgary, Canada, said yesterday it had uncovered the hammers, dated to that time, in the West African country of Ivory Coast. It would be the earliest known use of tools by chimpanzees. The hammers were used to crack nuts, a behaviour still seen in chimps in that area, the researchers say in a paper in the online edition of Proceedings of the National Academy of Sciences. They say the finding may indicate that a ‘chimpanzee stone age’ began in ancient times. The earliest reports of stone-tool use by chimpanzees in the area date to the writings of Portuguese explorers in the 1600s. The stones are about the size of rockmelons with patterns of wear indicating use to crack nuts, the researchers say. The rocks would have been too large for human hands, but about right for the larger, stronger hands of chimpanzees. ‘It’s not clear whether we hominids invented this kind of stone technology, or whether both humans and the great apes inherited it from a […]