As you read these words, Planet Earth teems with trillions of life-forms, each going about its own business: eating, reproducing, thriving . . . Yet, the life of almost every single organism draws nearer to certain death. On the other hand, suicide inside the mitochondria that live within us results in the death of millions of cells each second for our own good Why is death such a universal companion to life on Earth? Why haven't animals evolved to break free of its shackles?

In this wide-ranging exploration of death, Jules Howard attempts to shed evolutionary light on one of our...