Not long ago, we thought decoding the human genome would reveal the secrets of life. That proved to be a fantasy. Now scientists are learning how to grow life outside the body — and as science writer Phil Ball discovered, even create mini-brains in a vat.

Melanie Challenger is a naturalist who spends a lot of time in wild places. She’s intimately familiar with birth and death, and she believes any understanding of what it means to be human must start by tuning into our animal nature.