JohnInKansas, thanks for psoting that link to that http://www.americanscientist.org/template/AssetDetail/assetid/28341 article.

Here's an excerpt from that article that I found particularly interesting:

"When the DNA samples were analyzed, decoded and compared to the subject's cor [skin color], the Brazilian population showed a surprising deviation from the earlier Porto [European] and São Tomé [African] control experiments. In samples from both urban centers and rural districts, the distribution of African alleles was the same for the "black" and "intermediate" Brazilians: Both groups' average AAI values fell between the European and African ends of the spectrum. There was wide variation in the samples—some of the individuals in these groups even showed AAI values in the same range as the Portuguese controls; others resembled the São Tomé Africans. In other words, racial appearance had no relationship to the degree of genetic identity with either the Europeans or Africans. According to Pena "We were surprised at the very poor correlation, but we should not have been. From an ancestry point of view there is almost complete mixture [between Europeans and Africans in the population]."
-snip-

Here's another excerpt from that article:

The white Brazilians also showed a high proportion of African allelic markers, although the distribution was not as pronounced as in the black and intermediate groups. The reason for this became apparent when the identity of the markers was considered—the OCA2 gene, part of the test battery, encodes a protein that regulates pigment production, meaning that the marker itself contributed to the phenotype. When this site was excluded from the AAI calculation, there were no significant differences in the African genomic ancestry of black and white study participants.

Does the same genetic pattern exist in the United States, which also has a large population of African descent? Probably not, says Mark Shriver at Penn State University, whose lab developed the marker set used by Pena. As Shriver points out, "there was no such thing as a one-drop [of blood] rule in Brazil," meaning that Brazil never developed the emphasis on ancestry over appearance that is found in its North American neighbor. As a result, mixed-race marriage per se did not carry the same social stigma in Brazil as it did in the United States. Pena agrees with Shriver's characterization of racial genetics in the U.S., but adds that more work is needed to distinguish the social and genetic elements of race."

-snip-

If such a study were done in the USA, my unscientific prediction would be that there would be plenty "White" people who would have African allelic markers. I seem to recall reading that such a study was done in South Africa some time ago, and some White South Africans were found to have African markers...

The American definition of who is Black {in this context,
I mean "African American"} is that a person who has any Black African ancestry is Black. Another way to say this is that "one drop of 'Black blood' makes a person Black".

Imo, this definition is at its core racist as it considers Black African ancestry to be a contaminant. One way that this "one drop of Black blood" makes a person Black" definition could be challenged and eradicated is for those people of mixed White/Black ancestry whether it be first generation or not to declare that they are White no matter how dark their skin color is and not matter how tightly curled their hair is.

However, since visual clues are so heavily used by people in the United States {and elsewhere?} to determine other people's racial category, having dark skinned people declare that they are White, might get very interesting.

But since racial self-identification has been the recent practice at census times and at other times, as long as mixed race people who are declaring their Whiteness aren't rejecting Blackness because they consider it less than White, I'm all for this approach.

But then again, there is power in numbers. And since so many of us are mixed race, politically African Americans would suffer if droves of people who are now thought of [and who think of themselves]
as being Black left to join a White or a Mixed Race category.

So, I may need to re-think that "declare yourself White or Mixed Race" approach.