Animals do make use of tools for getting food or for protecting themselves. Apes reach for sticks or stones when threatened, sea otters break their favourite food, the shells, with the help of stones, and a species of finches picks out insects from tree trunks, with a long cactus quill. For generations the young ones of animals have watched the traits of the adults and imitated them exactly. Humans, on the other hand, may change the traits according to personal requirements. Humans advance and discover new things by adapting and learning. It is hard to believe that the hand axe made by prehistoric man out of stone has today given rise to sharp knives, chainsaws, and many other things.