Who's your great, great, great granddaddy?

There may come a time, perhaps even within our lifetimes, when treatment for our illnesses will depend upon our very own unique genealogy. At least, that is my take away from a fascinating story about human genomes that is in the news today.

The New York Times detailed how scientists have decoded the complete genomes of five individuals from southern Africa. The Africans included four Bushmen hunter-gatherers and one member of the Bantu tribe. None of the Bushmen would likely be known outside of their own communities, but the Bantu individual is very well-known indeed. He is Archbishop Desmond Tutu.

Archbishop Tutu is said to have been selected because he has a very keen interest in medicine and in the human genome project and he fit the profile that was needed for the research. His parents came from the two largest Bantu groups in South Africa, the Sotho-Tswana and the Nguni.

African genomes are of particular interest to scientists because they have more variation in their DNA than other populations. Everyone from outside of Africa is descended from a small group of pilgrims who left that continent and ultimately colonized the world, beginning some 50,000 years ago. Thus, the genomes of all these people were drawn from a smaller pool and are fairly uniform. But the vast majority of humans who stayed behind on the mother continent and who were the ancestors of today's Africans represent a great diversity of genomes.

The Bushmen are especially fascinating because their ancestors branched off from the main line of human ancestry earlier than anyone else. Researchers found that most of the variations in their genomes were acquired after that great branching.

The Bantu, Archbishop Tutu, actually turned out to have Bushman mitochondrial DNA. (Mitrochondrial DNA is the genetic element that is passed down through the female line.) Apparently, this DNA came into his ancestry in the very distant past because the rest of his genome proved to be Bantu.

The practical application of all this genome research is to find ways to more effectively treat disease. By studying a person's genome, doctors may well be able to tailor their medicines and therapies to the individual's genealogy. So in the future, the pills we take may very well be determined by who was our great, great, great granddaddy. Or, even more likely, our great, great, great grandmother.


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