There’s a cave in Ethiopia, in an area called Dikika. At some point, around 3.4 million years ago, an early hominin made some incisions on an animal carcass, leaving some notches on a bone as the makeshift knife cut past the muscle and sinew into the bone, tell-tale kerf marks that speak of the first time one of our ancestors used a tool. 1 What happened in that cave changed everything for our species. 1 McPherron, S.





