1. By the time Homo sapiens evolved about 200,000 years ago, they were already expert hunters. Tim Flannery in his celebrated book Here on Earth (2010) described how human ancestors in the course of inhabiting the world outside Africa wiped out scores of large animals that are now known only from their fossils.

2. These three documented behaviors were (a) “clubbing,” or striking out with a stick, sometimes used against other chimpanzees but also used against snakes, baboons, and leopards; (b) “aimed throw,” or throwing an object (often inaccurately) at another chimpanzee, a leopard, or monkeys; and (c) “drag branch,” or running while dragging a large branch during an aggressive display.