Tag Archives: population genetics

The Legacy of Slavery in African American DNA

This week at Pacific Standard,  I discuss a recent study that examines the influence of slavery and its discriminatory aftermath in the genetic diversity in over 4,000 African American genomes. One of the most striking results of the study is probably the most obvious: On average, about 15% of the DNA of African Americans is of European origin – and, according the researchers’ best statistical model, that European DNA largely dates back to before the Civil War. That was a time when interracial sexual relations overwhelmingly took the form of whites raping black slaves. After the Civil War, according to the model, admixture between blacks and whites dropped off sharply.

Like I said, it’s not particularly surprising, but the breadth of the genetic legacy of slavery is striking.

The study makes some other intriguing suggestions about African American genetic history, especially regarding the enormous demographic shift of the Great Migration (~1915-1970), when 6 million African Americans left the South and settled in other parts of the country. The big takeaway from this study is that African American genetic history is one of coercion: coerced migration and coerced sex over a relatively short period of time, which left strong signals in the genetic diversity of present day African Americans.

Aside from the historical aspect, studies like this matter if African Americans are going to participate in the ongoing development of personalized genomic medicine. Because the genetic structure of the African American population differs from that of whites, African Americans have different genetic risk factors for disease – and even different risk variants for the same diseases. Studies like this lay the groundwork for an inclusive practice of genomic medicine.

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“…there is no support from the field of population genetics for Wade’s conjectures.”

If you are a regular patron of The Finch & Pea, you know that Nicholas Wade’s controversial book, A Troublesome Inheritance (link is to David Dobbs’ unflattering review), is a work of pseudoscience that purports to draw on the fields of human and population genetics to support a panoply of racist stereotypes. Now, a lengthy list of leaders in these fields, tired of their work being misappropriated, have signed a letter asserting:

We are in full agreement that there is no support from the field of population genetics for Wade’s conjectures. – Graham Coop, Michael Eisen, Rasmus Nielsen, Molly Przeworski & Noah Rosenberg (+134 signatories)

As Mary Carmichael notes, this is probably the first time these 139 scientists have ever agreed on anything.

*Hat tip to Daniel MacArthur.

REPOST: Imagine if Sex Were Only for IQs Over 120

At the request of my co-blogger Mike, I’m reposting this article which originally appeared at Science 2.0 on 30 December 2008 where some authors of the paper in question respond in the comments during the run-up to the publication of their book The 10,000 Year Explosion.

Unfortunately for all of us still breathing braniacs, the title only applies to those of us who are also medieval Ashkenazi Jews, according to the authors of the 2006 paper “Natural History of Ashkenazi Intelligence”.

Discussing “race” and intelligence is always a touchy subject and definitely not politically correct; but science should not be fettered by the chains of political correctness like a mangy circus lion.  It must run free across the intellectual savanna, striking down the juvenile wildebeest of ignorance. Following articles on the biology and significance of race by Michael White, Massimo Pigliucci, and moi, my attention was directed to “Natural History of Ashkenazi Intelligence”.  Thanks to press attention from biological research bell-weathers like The Economist and the New York Times, as well as discussion on National Public Radio, this paper has gained Goodyear AquatredTM-esque traction on the internet. Continue reading