Hand Axes as an Extended Phenotype

Two and a half million years ago, our small-brained ancestors evolved the ability to knock flakes from rocks to use as cutting edges. By doing so, they could also make the rocks themselves useful as choppers. This basic tool kit of flakes and choppers served the needs of hunting and gathering for a million years. Then, around 1.6 million years ago, a medium-brained African hominid (Homo erectus) evolved the ability to produce an extraordinary object that archeologists call a handaxe. A handax...