Monday, April 14, 2008

Deep ancestry

I've been reading Deep ancestry: inside the Genographic Project: the landmark DNA quest to decipher our distant past, by Spencer Wells. Published by National Geographic, Washington, D.C., 2006.

DNA sequencing earned a Nobel Prize as recently as 2000. This is a new field of research.

First was the discovery of mitochondrial DNA, passed from mother to daughter. In 1987, Newsweek carried the report of the research identifying "Eve." The geographic source of the mitochondrial DNA was Africa. And Eve was surprisingly young -- lines from her diverged between 200,000 and 170,000 years ago. For awhile, it was believed that Eve might have lived in Asia. But in 2000, research nailed it down: Eve was definitely from Africa (south or east central).

The Y-chromosome, passed from father to son, for a long time was more difficult to track. It wasn't until new sequencing techniques came along that variances in the male genome could be better tracked. And here was the second surprise: our oldest common male ancestor, from whom all other men come, appeared 60,000 years ago (also African, probably from somewhere close to modern day Ethiopia).

As the author asked, so what was Eve doing from 170,000 to 60,000? Just waiting for a date?

Answer: there is "variance in reproductive success." It was an early human sexual practice that while most women reproduced, many men did not. Back then, the men likeliest to reproduce were the chief, tribal boss, or traveling conqueror. Today, of course, we have evolved: you have to be a cult leader or rock star.

All told, the history of mankind -- all variance in skin color, skull shape, culture and technology -- comes from just 2,000 generations of human history.

Sometime this year, I'm going to scrape the inside of my cheek and send it off for analysis. There's a family rumor that we have Indian ancestry; here's how we find out.

For more information on this most fascinating history of the migration of our species, our one, big, unified human family, see here, or click the title of this entry. To order the DNA analysis kit ($99.95, anonymous), follow the links to Your Genetic Journey.

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