A manly march out of Africa

I like to imagine what life might have been like for our ancestors.  You can do this with any time period — going back to your great-grandparents, or a few centuries before that, or way back in evolutionary time.  In today’s case, how about 60,000 years ago?

That’s the era when Homo Sapiens were migrating from the Africa to the Middle East, and spreading from there to populate Asia, Europe, Australia and the Americas.  These people were anatomically the same as us.  And it’s surprising how much anthropologists have been able to deduce about them:  They were hunter-gatherers, and probably their lives were similar to hunter-gatherer communities that persisted into the 20th century.

And now there’s evidence that the bands of migrating humans, who probably worked their away across what we now call Egypt and the Sinai, included more men than women.  Alon Keinan of Harvard Medical School, and colleagues, used genetic markers to detect a surprising anomaly in human DNA that must have been triggered about 60,000 years ago.

They compared the genomes of modern people of West African descent with people of European and Asian descent.  The non-Africans show a series of random changes in their X chromosomes, known as “genetic drift,” which only seems to make sense if non-Africans all descended from a group where men outnumbered women.

(I’m skipping over the scientific methods for making these calculations, but it’s worth noting that this type of analysis is possible only using the tools developed for the Human Genome Project.)

We may never be able to say with confidence why those bands of people left.  A writer at New Scientist speculates that warfare might have played a role — that the migrants might have been similar to marauding Vikings.  Or, at the least, they may have been like more recent examples where male explorers and settlers went first (and women were in short supply).

This doesn’t imply that gender relationships back then were structured in any specific way.  But, it’s fair to imagine a charismatic leader, a visionary, whose name we’ll never know, who led early exploring parties up the Nile River, and out of Africa — 60,000 or more years ago.  The first “age of exploration”?

The study was published this month in Nature Genetics.

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About Admin

I was the Science & Health Reporter for 12 years, and the Environment Reporter for 5 years, at NPR member station KPLU, in Seattle, WA (now re-born as knkx). Today, I've left journalism but keep this blog as a place for writing about some of the topics that I tracked over the years.

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