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April 30, 2005

Wuz your ancestry?

The Christian Science Monitor has a decent article about the ancestry industry, which breaks down your ancestral fractions. For 99% of people this won't tell them anything new, so the quote that "1/3 of people found significant mixture" is indicative to me that a lot of people who have doubts are the ones getting these tests done. Additionally, this snip is also informative:

"My mother looked like she walked out of Saudi Arabia," he says. "And my brother looks very Arabic, like someone out of 'Lawrence of Arabia.' " So he took the second test, which broke down his European background as 45 percent Northern European, 25 percent Middle Eastern, 25 percent Mediterranean (Greek/Turkish), and 5 percent South Asian. Though his brother has a darker complexion, he tested for nearly identical ancestral DNA markers, Kennedy says, just as would be expected of two brothers.

Obviously there is no reason that the functional genes that cause the "dark" phenotype in question are going to correlate well with ancestral markers between siblings,1 but in any case, though this individual got a "hit" that "explains" the out-of-the-norm phenotype for his family based on their ancestry...I suspect there are many swarthy individuals of British ancestry out there who didn't find anything interesting. After all, as I've noted many a time, the tribal peoples of the Welsh highlands were so dark that the Romans assumed they must have been branch of the Iberian peoples (they were somewhat right).

1 - If you could intuit ancestral portions just from phenotype, why are you getting the test anyhow? In any case, over generations a tight linkage between various markers that are normally correlated with particular ancestries and phenotypes can break down due to recombination.

Posted by razib at 11:29 AM