Friday, September 30, 2011

My DNA -- a personal story

I couldn't have written this a few years ago. Recently I sent in DNA samples to two organizations to see what they could find. The first one was National Geographic's Genographic Project which geographically traces either the paternal or maternal line back to Eastern Africa about 50,000 years ago, about the time homo sapiens took the "Great Leap Forward," developed language and culture and distinguished themselves from the other hominoids, and left the continent.

National Geographic use genetic markers, mutations on the Y chromosome, to track the male lineage. For females, they use the mitochondria. I ran the test for my Y chromosome which, because only males have one, is transferred intact from the man to his son. No shuffling like the other chromosomes; they only change by mutation.

A few weeks later I received my map, below

My ancestor crossed the Red Sea 40-50,000 years ago, and moved either northeast into modern day Pakistan or northwest into modern Turkey, My haplogroup -- my "tribe," as best as they can tell, is G-M201 of the more ancient M168, P143, and M89 lineage. Today, thirty percent of men in the Caucus Mountains, 14% in Sardinia, 10% in northern Italy, 8% in northern Spain, and 7% of Turkish men are my haplogroup brothers.

Now I'll share a little family secret, or least a family suspicion. Some of us have noticed what appear to be African facial features in some relatives, and by induction my paternal grandmother's line seems implicated. At times, in certain light, she looked like a black woman. And I remember doing a double take on a photo of Mobutu Sese Seko, infamous leader of Zaire, thinking it was my uncle in a funny hat. I'll admit there was a little inclusive pride surrounding this family curiosity.

With National Genographic Project I thought, here is an opportunity to see if it was true. My grandmother, you see, had come from  Kentucky and although they weren't wealthy and I've never heard rumor, it's possible that one of her ancestors at some point owned slaves. There would have been slaves in that area, at any rate.  I've read that if a white man impregnated a black slave and the children were light enough skinned they were sometimes raised in the father's home. This would be great taboo for all sorts of reasons, of course, and it seems likely in the prim southern culture such a secret could die within a generation or two, leaving just the genetic trace which I have mentioned.

Her maiden name couldn't be more Scotts/Irish: O'Bannon but surnames were almost always attached to the Y chromosome, not to the mitochondria which I could now trace.

A short biology lesson.   Mitochondria are the little "cells-within-our-cells," at one time actually invading bacteria, most people believe. They create heat and more important, they package up energy as adenosine triphosphate (ADP), which is sent around the body to do work. The mitochondria are essential to almost all organisms with a nucleated cell: the "eukaryotes."

For the present purpose two things are most relevant. One is that the mitochondria only get passed on from the mother. Males get them, and they become the organelles which propel sperm, but jettison before entering the egg. Matt Ridley, in his excellent "The Red Queen," explains that, in essence, male and female organelles will fight (chemically) if they encounter one another in the egg, so have come to an agreement -- so to speak -- that the males' will not enter. The second thing about mitochondria is that they carry their own DNA. It's circular and there are up to ten copies in each cell, but for reasons explained above it's passed on intact -- except for mutations. National Geographic is able to trace the female line back through time this way, using the mutations or "markers" to do so.

My grandmother is no longer living. But note that while mitochondria are not passed on through males it is passed on to males, so I asked my father to swab his cheek to have her mitochondria genographed, and he did.

Our reasoning went like this: 1) IF there was black blood in the genome it probably happened during slavery. 2) it probably would have been between a white man and a black woman, and 3) if the lineage from that event to my grandmother involved only daughters, then the Genographic Project would trace my father's maternal line back through the black woman in recent history and straight to Africa from there. We might stand to learn which part of Africa some of my ancestors may have come from.

My father's maternal "haplogroup" was U4. It didn't come straight from Africa.

My grandmother's female heritage moved north to Eastern Europe about 50K years ago. So while we don't know there was an interracial affair on my grandmother's side we still don't have any evidence that there wasn't one; a single male along that lineage would sever the mitochondrial chain.

Another thing I didn't learn was much about myself. In each generation, each parent passes on half their DNA to child and the other half comes from the other parent. Of course. So, using the mitochondria test for example, the entire male half of my heritage is lost -- 50% right away. But not only is the father is ignored, so are both of his parents and all their ancestors too. And the mother's father and all his heritage is trimmed off and this happens for every generation -- so what National Geographic has done is lay down a single rather arbitrary thread of ancestry for me, among many pruned branches. All I know is one of my ancestors seemed to have traveled out of Africa 50,000 years ago, moving north.

But at a generous average of 20 years a generation, in 50,000 years there've been 2,500 generations. Raise 2  to the power of 2,500 and you get 375 followed by 749 0's , each of whom would be just as relevant to my own genome as the woman who first rafted across the Mediterranean.  But oddly, back then humans numbered in just tens of thousands.  How do we reconcile these two numbers?  In a word, as Bill Bryson put it in A Short History of Neary Everything: incest, naturally.  And a lot of it. Fortunately most of it was so far removed to not matter a whit, but all told we can conclude that my ancestry is much more convoluted than the thread National Geographic was able to trace, but it's still of academic interest and that's good enough for me.

This brings me to the next study of my genome, done by a company called 23andme which focuses on health. Their report is even more impressive. By referencing medical literature they report how likely the average person is to get any of almost 200 hundred diseases. They indicate how inheritable each disease is, and how much is environmental or behavioral and how certain scientists are of these measures. Then, after looking at your genome they report how susceptible you are, compared to average, and how certain they are of that! Some diseases are highly heritable, the relevant genes few and obvious, the studies are highly reliable, the diseases are devastating, and there's nothing you can do about it. I figured if I had one, I'd recalibrate my personal clock. If you are brave enough to look, I think it's a valuable service.

But I'm concerned here with a minor report from 23andme, a map of my "haplogroups" set at 500 years ago. That is, a map showing where "my people" were living before they could travel intercontinentally with relative ease. Like the Genographic Project, and with a similar method, 23andme did this for both my maternal and paternal sides.

So, before they could sail, my mother's mother's people were scattered around northern and eastern Europe. This sounds plausible; my mother is 100% Czech. My father's father's side was scattered in smaller more concentrated groups in southern and Eastern Europe, western Asia, the Middle East (he claims to be German, Irish, and Scottish). Interesting, they are also in northern Africa.

Well I might have found where those admirable black features came from, after all.


  1. Fascinating information Professor Howenstine, my sole brother. lol. Wow, I always wanted to trace my genealogy. This blog is wonderful, and it gives me some direction. How much did all this coast you? I have mad (lots of) question about this.


I've allowed comments without login.