Why are most of us born with one nose, two legs, ten fingers and twenty-four ribs – and some of us not? Why do most of us stop growing in our teens – while others just keep going? Why do some us have heads of red hair – and others no hair at all? The human genome, we are told, makes us what we are. But how?

Armand Marie Leroi takes us to the extremes of human mutation – from the grotesque to the beautiful, and often both at the same time – to explain how we become what we are. Through the tales of long-lived Croatian dwarves, ostrich-footed Wadoma tribesmen, sex-changing French convent girls, and many more wonders of human development, Leroi has written a brilliant narrative account of our genetic grammar and people whose bodies have revealed it.