The Earth teems with life: in its oceans, forests, skies and cities. Yet there's a black hole at the heart of biology. We do not know why complex life is the way it is, or, for that matter, how life first began. In The Vital Question, award-winning author and biochemist Nick Lane radically reframes evolutionary history, putting forward a solution to conundrums that have puzzled generations of scientists.

For two and a half billion years, from the very origins of life, single-celled organisms such as bacteria evolved without changing their basic form. Then, on just one...