Sunday, March 31, 2013

Who's Your Distant Ancestor?

Back when I was in grade school, I remember one of my sisters preparing a display for her high school science fair project. In that project, she compared Neanderthals to Cro-Magnons. I don’t remember what kind of grade she received, but I found her project fascinating. Two types of humans, living at the same time! I wondered what their interactions would have been like.
Since then, the same question has been explored in various medias. Jean Auel’s Clan of the Cave Bear made a big splash with readers as it followed the life of a young Cro-Magnon, also known as a modern human, who was raised by Neanderthals, if I remember correctly. Various educational shows on TV have been made about the Neanderthals, the Homo Sapiens, how they were different, how they were alike, and how they might have interacted before the Neanderthals died out.
The impression I’ve gotten over all these years was that scientists didn’t feel these two species of humans had interbred, and I wondered why they thought that way. Neanderthals are depicted as kind of squat, hairy, with a heavy brow, broad noses and receding chins. I could look around and see people who had those attributes, although it’s usually one per person, not all of them. But no, it seemed we were determined to blame our own ancestors for killing the last of the Neanderthals.
At last, a skeleton has been discovered in northern Italy that appears to be that of a mixed breed. Although mostly that of a modern human, the jaw displays a receding chin. The DNA reveals this person had Neanderthal mitochondrial (maternal) DNA. So it would seem the two species did interbreed, at least once.
Which opens up a whole new mess of ancient ancestors we didn’t realize were in the gene pool.
Sometimes when I’m working out the background for a story, I pick 2 or 3 genetic things to track throughout the population and then work out how those attributes manifest in the population over the generations. The gene for dark hair, for instance, will dominate a gene for lighter hair, and blond will dominate red hair. But after a few generations of almost all the people having dark hair, you will start getting a generation or two of lots of blonds, and a few redheads will crop up. The number of blonds will ebb and flow; the number of redheads tends to remain fairly steady.
I never thought to track the occurrence of receding chins.

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