A-Z Challenge 2013: X is for eXtreme Genealogy

OK, so I cheated a little bit,and today's post is the same one as last year's "X is for..." - because, after all, X is a pretty hard letter!  The original post can be found here, but here it is again:

You've heard of extreme sports? even extreme ironing? so how about extreme genealogy?  The BBC defines Extreme Genealogy as the art and skill of DNA testing:

The firm is the brainchild of the Oxford University geneticist Bryan Sykes, who [several] years ago published research showing that everyone of European extraction could trace their ancestry back to one of seven women who lived 40,000 years ago. Such was the demand from the public to know which of the "seven daughters of Eve" they were descended from, Professor Sykes spotted a business opportunity."

• Europeans mostly come from one of seven women
• About half are from Helena, who lived in the Pyrenees 20,000 years ago
• Among non-Europeans, 29 such clans have been identified
• These include 12 among those of African origin
• Four among Native Americans
• And nine among Japanese