Skip to comments.Genetic study clarifies African and African-American ancestry
Posted on 12/21/2009 12:41:48 PM PST by Pharmboy
The University of Pennsylvania
Sarah Tishkoff, professor in the departments of genetics and biology at University
of Pennsylvania, is collecting samples in Africa.
Collaboration by University of Pennsylvania and Cornell University
PHILADELPHIA - People who identify as African-American may be as little as 1 percent West African or as much as 99 percent, just one finding of a large-scale, genome-wide study of African and African-American ancestry released today.
An international research team led by scientists from the University of Pennsylvania and Cornell University has collected and analyzed genotype data from 365 African-Americans, 203 people from 12 West African populations and 400 Europeans from 42 countries to provide a genome-wide perspective of African and African-American ancestry.
The data reveal genomic diversity among African and African-American populations far more complex than originally thought and reflect deep historical, cultural and linguistic impacts on gene flow among populations. The data also point to the ability of geneticists to reliably discern ancestry using such data. Scientists found, for example, that they could distinguish African and European ancestry at each region of the genome of self-identified-African Americans.
Sarah Tishkoff, a geneticist at Penn, and Carlos Bustamante, a computational biologist at Cornell, led the study to analyze 300,000 genetic markers from across the genome from West African, African-American and European-American populations to see whether they could reliably distinguish ancestry.
The team found that, while some West African populations are nearly indistinguishable, there are clear and discernible genetic differences among some groups, divided along linguistic and geographic lines.
This newly acquired genetic data revealed a number of important advances, including:
The rich mosaic of African-American ancestry. Among the 365 African-Americans in the study, individuals had as little as 1 percent West African ancestry and as much as 99 percent. There are significant implications for pharmacogenomic studies and assessment of disease risk. It appears that the range of genetic ancestry captured under the term African-American is extremely diverse, suggesting that caution should be used in prescribing treatment based on differential guidelines for African-Americans. A median proportion of European ancestry in African-Americans of 18.5 percent, with large variation among individuals. The predominately African origin of X chromosomes of African-Americans. This is consistent with the pattern of gene flow where mothers were mostly of African ancestry while fathers were either of African or European ancestry. A technique which can reliably distinguish African and European ancestry for any particular region of the genome in African-Americans. This could have implications for personalized ancestry reconstructions, personalized medicine and more effective drug treatments and could aid in developing more effective methods for mapping genetic risk factors for diseases common in African-Americans, such as hypertension, diabetes and prostate cancer. The similarity of the West African component of African-American ancestry to the profile from non-Bantu Niger-Kordofanian speaking populations, which include the Igbo and Yoruba from Nigeria and the Brong from Ghana A comparison of the West African segments of African-American genomes. This is wholly in line with historical documents showing that the Igbo and Yoruba are two of the 10 most frequent ethnicities in slave trade records; however, most African-Americans also have ancestry from Bantu-speaking populations in western Africa. Population structure within the West African samples reflecting primarily language and secondarily geographical distance, echoing the Bantu expansion from a homeland in West Africa across much of sub-Saharan Africa around 4,000 years ago.
"Africa, which is the homeland of all modern humans, contains more than 2,000 ethnolinguistic groups and harbors great genetic and phenotypic diversity; however, little is known about fine-scale population structure at a genome-wide level," said Tishkoff, professor in the departments of genetics and biology at Penn. "We were able to distinguish among closely related West African populations and showed that genetically inferred ancestry correlates strongly with geography and language, reflecting historic migration events in Africa.
"We were also able to show that there is little genetic differentiation among African-Americans in the African portion of their ancestry, reflecting the fact that most African-Americans have ancestry from several regions of western Africa. The greatest variation among African-Americans is in their proportion of European ancestry, which has important implications for the design of personalized medical treatments."
The study focused primarily on the genetic structure of West African populations, as previous genetic and historical studies suggested that the region was the source for most of the ancestry of present-day African-Americans. The results suggest that there are clear and discernible genetic differences among some of the West African populations, whereas others appear to be nearly indistinguishable, even when comparing more than 300,000 genetic markers. The researchers note that a larger sample size would likely reveal further substructure and diversity between these populations.
Analyzing patterns of population structure and individual ancestry in Africans and African-Americans illuminates the history of human populations and is critical for undertaking medical genomic studies on a global scale. Understanding ancestry not only provides insight into historical migration patterns, human origins and greater understanding of evolutionary forces, but also allows researchers to examine disease susceptibility and pharmacogenic response, and to develop personalized drugs and treatments, a frontier in public health.
There is also strong reason to believe that high-density genotype data from African and African-American populations may pinpoint more precisely the geographic origin of African ancestry in African-Americans, the researchers said. The study appears online in the Proceedings of the National Academy of Sciences.
The study was funded by the National Institutes of Health, National Science Foundation, David and Lucile Packard and Burroughs Wellcome Foundation.
Research was conducted by lead author Katarzyna Bryca and Adam Autona of the Department of Biological Statistics and Computational Biology, Cornell; Matthew R. Nelson of GlaxoSmithKline; Jorge R. Oksenberg and Stephen L. Hauser of the Department of Neurology, University of California, San Francisco; Scott Williams of the Department of Molecular Physiology and Biophysics, Vanderbilt University; Alain Froment of the Unité Mixte de Recherche in Paris; Jean-Marie Bodo of the Ministére de la Recherche Scientifique et de l'Innovation in Cameroon; Charles Wambebe of the International Biomedical Research in Nigeria; and principal investigators Tishkoff and Bustamante.
Given the size of the African continent, I’d expect genetic diversity.
Was Mr. Reese paid by the word for this? He mostly repeated himself.
When writing a PR release, they usually write the quotes as well as the body of the piece...they spent a lot of time justifying the grant money, it appears.
KUNTA KINTE!... I HAVE FOUND YOU!...............
If Africa became prosperous then these Malthusians and Keynesians from western universities wouldn’t have jobs. Be assured that everything they do is calculated to keep Africa in poverty.
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They sure didn't do it with a COLB.
of interest ping
There are also significant implications for affirmative action and preferential college admissions.
THIS is the thing that will finally destroy such programs, as soon as someone can find a viable way to bring some sort of lawsuit.
Something not mentioned by this article is that there are a lot of "white" Americans who have some African ancestry; can't remember the source but I remember reading somewhere that that is true of something like 25% of "white" Southerners.
What we need to find is some blond-haired, blue-eyed person that tests out to have 5% West African Ancestry, and then demands to participate in some sort of Affirmative Action Program.
In the long-term Affirmative Action will collapse under the legal inability to define who gets preferences and who doesn't.
Is mixed race ancestry fairly typical for an American? In two ways, it is. First, more than 50 million whites, according to his analyses, have at least one black ancestor.
Another way to approach the question is to group together all the whites and blacks in America and calculate their mean degree of admixture. Shriver's data shows that on average, they would be about 12 or 13 percent African.
Yet, from another perspective, a sizable degree of racial mixing is highly unusual. There simply aren't many African-Americans or European-Americans who are mostly white but also substantially black. Shriver pointed out, "There is a very small degree of overlap in the population distributions." In America, most of the whites are extremely European and most of the blacks are quite African.
Despite the notorious arbitrariness of the "one drop" rule, the actual American population conforms to its strictures surprisingly closely.
Granted, the "one drop" rule would be laughed out of existence if anyone attempted to impose it on a land with a more genetically blended population, such as Puerto Rico (which Shriver has begun to study). Yet, it appears possible that the rule survives in the U.S. because it's not too wildly inaccurate. Only a small fraction of the population is more than half, but less than 90 percent European.
Among self-identified whites in Shriver's sample, the average black admixture is only 0.7 percent. That's the equivalent of having among your 128 great-great-great-great-great-grandparents (who lived around two centuries ago), 127 whites and one black.
It appears that 70 percent of whites have no African ancestors. Among the 30 percent who do, the black admixture is around 2.3 percent, which would be like having about three black ancestors out of those 128.
In contrast, African-Americans are much more racially mixed than European-Americans. Yet, Shriver's study shows that they are less European that was previously believed.
Earlier, cruder studies, done before direct genetic testing was feasible, suggested that African-Americans were 25 or even 30 percent white. Shriver's project is not complete, but with data from 25 sites already in, he is coming up with 17-18 percent white ancestry among African-Americans. That's the equivalent of 106 of those 128 of your ancestors from seven generations ago having been Africans and 22 Europeans.
I've always read that Blacks living in the USA are ~ 25% European.
Thanks for the ping.
>> 17-18 percent white ancestry among African-Americans <<
Corresponds pretty closely to what I think I would have guessed, based simply on personal observation.
But what about Indian (”Native American”) ancestry? A lot of blacks have it, as do whites. A lot of African-Americans have what look to me like Indian facial features. And when it comes to whites, my experience indicates it’s hard to find a white southern family whose oral tradition doesn’t include an Indian ancestor (usually female) way back in the 1700’s or early 1800’s.
One sixth= 17%
rather than one fourth= 25%
would seem to be the updated figure based upon these results.
Thanks Pharmboy.Among the 365 African-Americans in the study, individuals had as little as 1 percent West African ancestry and as much as 99 percent.To all -- please ping me to other topics which are appropriate for the GGG list.
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The degree of genetic and linguistic diversity in Africa exceeds that in the New World Native American populations andthe Eurasian populations.
This is a phenomenon observed in other species where the area of origin of a particular taxon occurs.
In other words, one would expect this observation of Africans if Humans originated there.
Try Senator Mary Landrieu.
I think she looks like a blonde-blue-eyed African.
I could just see such glowing terms if discussing Caucazoid ancestry.
the loose knit thin one dimensional genetic base of Satanic ectoplasm that we have now know to be the basis of white ancestry was found today in of all places ..a sewer in front of a bordello in remote western China known to some as the Tarim Basin...details developing... Geraldo Rivera reporting