The chimpanzee, of all other living species, is our closest relation, with whom we last shared a common ancestor about 5 million years ago. These African apes make and use a rich and varied kit of tools, and of the primates they are the only consistent and habitual tool-users and tool-makers. Chimpanzees meet the criteria of culture as originally defined for human beings by socio-cultural anthropologists. They show sex differences in using tools to...