12 January 2009

DNA: The essence of life

Today's New York Times Magazine carried an article, "My Genome, My Self," by psychologist Steven Pinker, who has had his complete genome analyzed and placed on the Internet. He is Harvard College professor of psychology at Harvard University and the author of “The Stuff of Thought: Language as a Window Into Human Nature.”

One of the perks of being a psychologist is access to tools that allow you to carry out the injunction to know thyself. I have been tested for vocational interest (closest match: psychologist), intelligence (above average), personality (open, conscientious, agreeable, average in extraversion, not too neurotic) and political orientation (neither leftist nor rightist, more libertarian than authoritarian). I have M.R.I. pictures of my brain (no obvious holes or bulges) and soon will undergo the ultimate test of marital love: my brain will be scanned while my wife’s name is subliminally flashed before my eyes.
Pinker volunteered for biologist George Church's Personal Genome Project (PGP), a public database which will contain the genomes and traits of 100,000 people. The PGP wants to involve geneticists in an international effort to "sift through genetic and environmental predictors of medical, physical and behavioral traits."

While the majority of the article focuses on genetic traits and probabilities, there is a section dealing with ancestry and genealogical issues:

I have known since 1972 that I am clean for Tay-Sachs, but the Counsyl screen showed that I carry one copy of a gene for familial dysautonomia, an incurable disorder of the autonomic nervous system that causes a number of unpleasant symptoms and a high chance of premature death. A well-meaning colleague tried to console me, but I was pleased to gain the knowledge. Children are not in my cards, but my nieces and nephews, who have a 25 percent chance of being carriers, will know to get tested. And I can shut the door to whatever wistfulness I may have had about my childlessness. The gene was not discovered until 2001, well after the choice confronted me, so my road not taken could have led to tragedy. But perhaps that’s the way you think if you are open to experience and not too neurotic.

Familial dysautonomia is found almost exclusively among Ashkenazi Jews, and 23andMe provided additional clues to that ancestry in my genome. My mitochondrial DNA (which is passed intact from mother to offspring) is specific to Ashkenazi populations and is similar to ones found in Sephardic and Oriental Jews and in Druze and Kurds. My Y chromosome (which is passed intact from father to son) is also Levantine, common among Ashkenazi, Sephardic and Oriental Jews and also sprinkled across the eastern Mediterranean. Both variants arose in the Middle East more than 2,000 years ago and were probably carried to regions in Italy by Jewish exiles after the Roman destruction of Jerusalem, then to the Rhine Valley in the Middle Ages and eastward to the Pale of Settlement in Poland and Moldova, ending up in my father’s father and my mother’s mother a century ago.

It’s thrilling to find yourself so tangibly connected to two millenniums of history. And even this secular, ecumenical Jew experienced a primitive tribal stirring in learning of a deep genealogy that coincides with the handing down of traditions I grew up with. But my blue eyes remind me not to get carried away with delusions about a Semitic essence. Mitochondrial DNA, and the Y chromosome, do not literally tell you about “your ancestry” but only half of your ancestry a generation ago, a quarter two generations ago and so on, shrinking exponentially the further back you go. In fact, since the further back you go the more ancestors you theoretically have (eight great-grandparents, sixteen great-great-grandparents and so on), at some point there aren’t enough ancestors to go around, everyone’s ancestors overlap with everyone else’s, and the very concept of personal ancestry becomes meaningless. I found it just as thrilling to zoom outward in the diagrams of my genetic lineage and see my place in a family tree that embraces all of humanity.

Those of us "into" DNA for genealogical purposes would have liked to learn about Pinker's haplogroup, markers, etc.

Read the complete article at the link above.

1 comment:

  1. Interesting article, and thank you for pointing it out to us.

    ReplyDelete