Why is the universe here? The answer, well known to philosophers, is, where else would it be? A more pertinent question is, why is the universe the way it is? For that, physicists can supply many and detailed answers about stars, galaxies and forces, from the quantum to the cosmic. There is enough, then, to distract us from an unanswered question much closer to home: why is life the way it is? This is the ‘black hole at the heart of biology’, says Nick Lane in his combative book The Vital Question.

Consider cells. These are the individually microscopic units from which we are all made. Although the trillions of cells in our bodies all have specialised functions – for example, nerve cells, liver cells or blood cells – they share a basic structure that’s much the same. Cells are surrounded by