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Matt Ridley is the author of provocative books on evolution, genetics and society. His books have sold over a million copies, been translated into thirty languages, and have won several awards.

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An ancient matin

Neanderthals may have contributed a few genes to posterity after all

Tantalising clues have been emerging for some time from human genomes that Neanderthals may have contributed a few genes to posterity after all. That `we' mated with `them' occasionally.

The clues come in the form of widely differing DNA sequences that seem to converge on common ancestors that lived long before modern human beings came out of Africa 80,000 years ago or so.

There is good reason to be cautious -- it is possible that it just means lots of very distantly Africans joined the migration -- but now it seems a tipping point is being reached in the debate. The latest study of 600 microsatellite (fingerprint) sequences from 2,000 people is being interpreted as evidence of two separate episodes of genetic mixing between Neanderthals (or heidelbergensis) and ex-African `moderns'. SeeNeanderthals may have interbred with humans.

John Hawks, who has good instincts in these matters, reckons the conclusion is probably right:

I take it as very likely that the strict out-of-Africa replacement without interbreeding is no longer credible. We've moved beyond it, and all these papers are testaments to that.

We will soon know much better when Svante Paabo publishes the Neanderthal genome, having extracted fragmented DNA from bones found in a Croatia and Spain.

The Implications of this are big, but it's important not to mislead. It means there were a few mixed-race people in Eurasia by 40,000 years ago and some of them had babies. But they were probably few. Few or none of those babies' descendants  ended up back in Africa. It means that some of the confusing skulls and bones from the `frontier' of African advance into Eurasia might be mixed-race. It means that there's a tiny bit of Neanderthal in some of us, but not all.

By the way, it's never been clear that Neanderthals were stupid. Their brains were often bigger than ours. But they did lack a fast-changing  tool kit, and they also lacked trade -- their artefacts never travelled far. Those two things go together. Trade creates a collective intelligence that far surpasses what individual brains can muster.