The differences between humans and chimps are vast. ‘We have bigger and more complex brains, fully-fledged language and writing, sophisticated tools, the control of fire, cultures that become increasingly complex, permanent structures in which to live and work, and the ability to walk upright and travel far and wide’, Cohen writes. And we differ not only in terms of our behaviour and how we live, but also in terms of our anatomy and susceptibility and resistance to different diseases. Chimps miscarry much less frequently than humans, and males ejaculate far more sperm. ‘A one per cent genetic difference accounts for all this?’, Cohen asks.