Re: [asa] Archaic inbreeding

Hi Glenn:

How would a gene which arose roughly 40,000 years ago be found in different
races which are believed to be separated by about 100,000 years?

~Dick

> "Like many genes involved with brain development, microcephalin has
> evolved
> rapidly in humans. In previous studies, Lahnshowed that one variant of
> microcephalin appeared about 40,000 years ago and has since swept through
> the population, propelled by the power of natural selection. The new
> variant
> is found in 70 per cent of living people. "We don't yet know exactly what
> this variant does or why it is being selected for - it could be something
> to
> do with cognition," says Lahn."
> "The obvious interpretation is that the new version arose 40,000 years ago
> via a chance mutation in the microcephalin gene. Lahn thinks otherwise. In
> a
> paper published last year, he looked at a haplotype within microcephalin.
> On
> the basis of sequence differences between the old and new versions of the
> gene, he concluded that the two are so different that they must have
> diverged at least 1 million years ago (Proceedings of the National Academy
> of Sciences, vol 103, p 18178)."
> "This combination of deep ancestry on one level and shallow ancestry on
> another suggests that something very unusual might have happened. It is as
> if the new version of microcephalin split off from our evolutionary
> lineage
> a million years ago, then jumped back in 40,000 years ago. According to
> Lahn, that is exactly what happened. By far the most likely explanation,
> he
> says, is that the newer version of the gene evolved in a separate species
> of
> human - probably Neanderthals - and then entered our lineage through
> interbreeding." Dan Jones, "The Neanderthal Within," New Scientist, March
> 3,
> 2007, p. 31

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Received on Sun Mar 11 12:24:07 2007