Everything Science Forum

Mitochondrial DNA Fails to Pinpoint African Ancestry (http://www.sciam.com/article.cfm?articleId=0006DF46-F9B0-152F-B9B083414B7F00A7)

Those hoping to trace their ancestry to a particular African tribe are unlikely to find a perfect match, according to a new genetic study. Researchers report that mitochondrial DNA isolated from African-Americans matched up to distinct African ethnic groups in fewer than 10 percent of cases, based on a partial database of African DNA samples. Broader or more probabilistic ancestries are still possible, however.

An individual's genes are a link to the past that stretches across any break in family name or birthplace through the generations. But not all genes are equally useful in tracing ancestries. The genes present on chromosomes are mixed extensively in every generation, making them a crude guide. In contrast, mitochondrial DNA is passed down from mother to child relatively unchanged, offering an individual the chance of identifying a distinct modern population, such as an ethnic group, having the same ancestors. Such reconstructions may still be imprecise, however, because mitochondrial sequences originating in one ethnic group can easily leak to others as women migrate.

Given the most current and, I believe, most popular thinking among paleontological anthropologists that modern humans originated in Africa, it follows that the current populations of Africa, or at least particular groups among them, would naturally have the greatest diversity of mitrochondrial DNA among their individuals. I suspect that this would also be a complicating factor in trying to pinpoint one's own African ancestry.

I wonder what ramifications this has towards the "Eve" theory of human origiins?

Just speculation, but -

I think the problem is that with mobility in modern Africa, people have intermixed over the last century.  Perhaps if DNA specimens had been collected hundreds of years ago, the populations were less intermixed and certain genetic patterns would have been geographically unique.

That shouldn't really matter in terms of mitochondrial DNA.  mtDNA is not unique in each person:  It gets passed from mother to offspring directly, with mutation occurring very rarely.  So, your mtDNA should be the same as your mother's, which should be the same as your grandmother's, which should be the same as your great-grandmother's, etc.

Then it would appear women have dispersed throughout Africa over the centuries so that it is difficult to tell where exactly a certain pattern of mDNA originated.  Dispersal may occur due to shortages of food or war, and possibly slavery.

The scientists in the field try to reconstruct mitochondrial "family trees" by  assumed mutation rates. There is no mixing of mDNA in reproduction, but the mDNA of separated populations can be expected to diverge at predictable rates, at least according to theory.