Thursday, September 15, 2011

Reflections on Human Evolution in Africa

Apologies to the readers of this blog for not giving an update for several months.

Over the last several months, I had a wonderful summer with my family, spending part of it in the Channel Islands of California which are not only very beautiful, but also of scientific interest because they were briefly connected to the California mainland by ice during the last ice age.  Plant and animal species such as an ironwood tree and a miniature fox show parallel evolution since the last glacial maximum from their mainland counterparts.

There have been several interesting scientific announcements since my last post, the most relevant that of Michael F. Hammer's work in which he postulates that contemporary Africans share a small amount of DNA with a branch of the human tree that split from the main branch of homo sapiens approximately 700,000 years ago.  He states that the estimates indicate that this event or events occured between 20,000 and 60,000 ya.

So now, contemporary Africans join contemporary non-Africans in showing traces of admixture with archaic humans sometime in the last 100,000 years.  This is certainly interesting.  Blogs and researchers are abuzz with discussions of Neanderthals, Denisovans and African admixture.  Researchers are mining the small portions of the genome that are inherited from these ancient admixture events.

I have to admit though, that I am a bit blase about it all.  It's too early to say, but thus far, the contribution to modern humans from these admixture events seems to be in very small quantities, at least since Africans and non-Africans have split. 

In my last post, I referenced the text The Archaeology of Africa: Food, Metals and Towns.  I've spent quite a bit of the summer reading this extraordinary book.  I am still not done. 

What have I learned?  For one, it is humbling to read this book and I can only begin by saying that we are ignorant of Africa, and stunningly so.

Hammer's research is only a first clue to the remarkable human diversity that must have existed across Africa.  If we are to comprehend the many times that humans and archaic humans walked out of Africa, we will have to look much deeper than we do now.  We will have to look in Africa and not just at the point of surmised departure.  It is in Africa that most of our genome evolved for most of its history.

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