Diamond's theory on the evolutionary course.

From the text:

History before the emergence of writing around 3000BC receives brief treatment, although it constitutes 99.9% of the five million year history of the human species. ..Humans diverged from the apes around seven million years ago. ..13 000 years since the end of the last Ice Age. (Diamond, Introduction)

Our closest living relatives are the three surviving species of great ape: the gorilla, the common chimpanzee and the pygmy chimpanzee (bonobo). Their confinement to Africa, along with abundant fossil evidence, indicates that the earliest stages of human evolution were also played out in Africa. Around seven million years ago, a population of African apes broke up into several populations, of which one evolved into modern gorillas, second into the two modern chimps and the third into humans.

Fossils indicate that the evolutionary line leading to us had achieved a substantially upright posture by around four million years ago, then began to increase in body size and in relative brain size around 2.5 million years ago.

The few preserved African skeletal fragments contemporary with the Neanderthals are more similar to our modern skeletons than to Neanderthal skeletons. Even fewer preserved East Asian sketal fragments are known, but they appear different again from both Africans and Neanderthals. (Diamond, p.38)