Ancient Chimps May Have Used Hammers  

Chimpanzees may have been using stone "hammers" as long as 4,300 years ago. An international research team, led by archaeologist Julio Mercader of the University of Calgary, Canada, said Monday it had uncovered the hammers, dated to that time, in the West African country Ivory Coast. It would be the earliest known use of tools by chimpanzees.

The hammers were used to crack nuts, a behavior still seen in chimps in that area, the researchers said in a paper in the online edition of Proceedings of the National Academy of Sciences.

The finding may indicate that a "chimpanzee stone age" began in ancient times, the researchers say.

The earliest reports of stone tool use by chimpanzees in this area date to the writings of Portuguese explorers in the 1600s.