Felipe Fernández-Armesto’s absorbing history of exploration – an ambitious history of humankind, in effect – begins with a premise many will find curious. On the very first page he posits an extraterrestrial observer characterising the history of Homo sapiens on earth. ‘The cosmic observer would surely say that our history was, above all, experience of increasing diversity,’ he suggests. That is not at all what my putative ET would deduce. He would define human history as an unbroken narrative of warfare and might reasonably conclude that we suffer from an addiction to bloodshed and conquest. Alternatively, he might consider the spread of humankind across the planet as akin to that of a particularly contagious virus. Either way, diversity wouldn’t come into it.