Human traffic

Carl Zimmer has just blogged some interesting work by Alan Templeton on the flow of human genes out of Africa. A result that doesn't surprise me is that there was a flow back and forth of genes between all existing human populations, even though there were several major movements, shown largely by mtDNA, out of Africa (four shown on the figure Zimmer reproduces), and several out of South East Asia more recently. Interestingly, Templeton's view is neither "pure" Out of Africa nor the competing "Multiregional Hypothesis" - erectus migrations did not end in simple extinction, according to Templeton, but neither were they the founding populations for Asian hominids. Instead they contribute genes, but the major flow out of Africa around 650-350kya seems to have swamped them.

We'll just have to await the published paper, but I find this supports a view I got from James Shreeves' The Neandertal Enigma that humans, us anyway, are adapted to long distance walking and are natural traders. And with trade goes genes. Even the Australian aborigines had a gene flow across the Timor Sea, and there were at least two, possibly more, waves of migration (the dingo, descended from the Asian wild dog, only arrived here 3000-5000 years ago).

This is a dangerous field to be working in - it goes to racial identities, claims of being the first nations in an area and so on, but it seems to me that as a species humans are born mongrels. There may very well be geographic variation - we expect that genes will tend to cluster about regions they are most adaptive - but there's no reason to think any population was isolated enough to form identifiable races the way, for example, a bird species might.