Natural selection, Darwin’s big idea, is elegantly parsimonious: all it assumes is, first, that parents pass on certain traits to their offspring and, secondly, that new traits arise every now and again. It follows that individuals who luck into traits that make them fitter are more likely to pass them on, while those lumbered with disadvantages are more likely to die out. Compared with the mind-boggling fundamentals of physics, the basics of biology are practically common sense – though it took a genius to point them out.

But the biological mechanisms that underpin those Darwinian assumptions are anything but common-sensical – as detailed by The Gene, Siddhartha Mukherjee’s follow-up to his Pulitzer Prize-winning first book, The Emperor of All Maladies: A Biography of Cancer. Its subtitle and prologue, in which Mukherjee recalls his uncles’ mental illnesses, suggest a personal narrative. But what follows is more intricate than intimate: a meticulous five-hundred-page account of how our genetic code was discovered and partially deciphered, intertwined with an equally meticulous exposition of what we can and can’t say about how it makes us who we are.

It is a long story. When it comes to heredity, Pythagoras got the ball rolling some two and a half thousand years before Gregor Mendel’s patient cultivation of his beloved peas established that it was packaged up in units – ‘genes’. Things moved more quickly after that: over the next