What distinguishes us from animals? Why did I scoop up a squashed hedgehog from the road this morning, on my dawn bike ride to the beach? The line between human and animal has never been clear, least of all in the medieval bestiaries that inspired Caspar Henderson’s magnificent new compendium. In those, men might have faces in their chests, or the heads of stags; virgins might be courted by unicorns; aristocrats claimed descent from bears. But Darwin didn’t make things any better. He not only proposed that we were once apes, but also that the whole of creation was and always will be in flux. Yet even Darwin was confounded by a peacock. What place was there in his system for such useless beauty?