See subjects.
Did you miss the lessson when it was explained we all come from Africa?
How about we limit the question to “descendants of people who lived in Africa within the last 1000 years”?
Are you looking for how many descendants of slaves are descendants of only Africans? Or, would you include naturalized citizens (white and black) from anywhere of the continent of Africa? Second generation Ghanaian living in the US? Naturalized South Africans?
I’m not saying I have the answers for any of this, but I’m curious as to what you’re after.
Is he talking about US citizens, or maybe Brazilian, or Venezuelan, or Cuban, or 30 other nationalities, or all in combination?
Ah, but what about people who reside in the US but are from other countries, either themselves or their parents?
There was a PBS program or series a while back on this topic (I think the host was Henry Louis Gates, but I might be mixing this up with another show). They did DNA (I think) testing of a bunch of African-American men in a southern town, and every single one of them had some European ancestry. These men were all different shades, including as dark as you are likely to see, but the shade had no apparent relationship to the percentage of European ancestry showing in their DNA.
They were all descendants of slaves, and the conclusion was that slave women were the victims of a lot of forced intercourse with whites and had a lot of mixed race children, who also ended up as slaves.
Of course, it was a pretty small sample (less than a dozen men, in a barber shop as I recall) but it was still an eye-opener.
Roddy
If you set the bar at 2,000 years, the answer to the OP’s question is possibly “None”
That would assume though that the most-recent-common ancestor was African.
Moderator Note
BrokenBriton, I think the intent of the question is quite obvious and your snark is not warranted. Let’s refrain from answers like this in the future.
Colibri
General Questions Moderator
There may be some, but the percentage is probably quite small. From here:
Obviously, this only applies to Black Americans whose ancestry dates back to before the end of slavery. More recent immigrants from Africa will often have only sub-Saharan African ancestry. And I wouldn’t put it in such absolute terms. There may be a few African Americans with only ancestry from Africa, but there are probably not many.
The MRCA concept is a little more subtle than the Wikipedia article makes it out to be, in my opinion.
I suspect the concept of the Most Recent Common Ancestor is not what you think it is.
The MRCA does not have a very direct bearing on the actual percent makeup of genetic material, and in fact it’s possible that no genetic material at all exists in a given individual from their (statistically-calculated) MRCA.
This is a rather long topic which I have explained elsewhere…see this paper if you are interested.
Some relevant quotes from the Rohde paper:
“After many generations, the proportion of genes contributed by each ancestor becomes vanishingly small, until some ancestors may contribute no actual genes…” (p 24)"
“The African sim has almost entirely African ancestry, with 0.00092% Eurasian ancestry, primarily from the border countries.” (p 27)
For clarification, it sounds like what the OP is asking is how many African Americans have genes derived only from pre L3 M/N-split populations (using mitochondrial lineages).
Quite a bit of research has been done around this; it’s impossible to say for any given individual because of the difficult of measuring every single gene. In general, the Self Identified Race/Ethnic group of “black” in the United States has an average of about 20% European gene admixture.
I should add that genes do cluster by SIRE groups, but to insist any particular gene is “pure African” or “pure European” is not a very satisfying way to put it.
I think it’s better to say that a given gene seems to have arisen after a particular given lineage split (using either mtDNA or Y-chromosome population/migration groupings) and that said gene is therefore represented predominately in the descendants of that population…for example, you would expect to find MCPH1 haplogroup D in “Europeans” commonly, but not in “Africans” because it didn’t show up until post-Africa populations.
Afro-European Genetic Admixture in the United States
How Much of the European Contribution to the African-American Genome Comes From Females?
The Rate of Black-to-White “Passing”
Can DNA Tell What “Race” You Are?
The Heredity of “Racial” Traits
The Rate of Black-to-White “Passing”
This is not intended as snark or sarcasm, but the question occurred to me of how many “white” Americans with non-immigrant ancestry are descendants of only Europeans? I’d imagine very few.
What do you mean by “non-immigrant ancestry”? All whites in the US have immigrant ancestry, of course.
In any case, from here
There should have been a <recent> in front of that phrase obviously 
And I wondering about native American as well, but neat link.