Anatomically speaking, contemporary humans appeared 130,000 to 160,000 years ago in Africa and began migrating out of Africa between 50,000 and 100,000 years ago; in Australia 50,000 years ago; in the New World 13,500 years ago; in Polynesia 1,500 years ago. In short, in the space of 100,000 years, sapiens colonized 70% of the planet, a feat that outstrips the colonizations carried out by other mammals by a factor of 10.
There are 6 billion of us, so the number of hominins (since 5 million years ago) who have lived would be of the order of 150 billion individuals. At a mutation rate of 7 × 10-5 per gene and per person, we should be seeing significant genetic diversity today. This is not the case, however, and implies that we are in fact derived from a small original population (around 10,000 individuals). Add to this the small number of genes we have, and it's clear that questions of regulation outweigh those of the quantity or nature of genes.
The question is often asked whether sapiens continues to evolve. The most spontaneous answer is no, which puts the onus on cultural and technical adaptation, on which I would have liked to close this year's lecture. But in fact, genetic evolution continues too. For example, the deletion of CCR5, a cytokine receptor, is increasing in frequency, no doubt or perhaps because it leads to resistance to HIV. In fact, infectious diseases are a powerful selective force in human evolution.
