I’ve already written more than I meant to—sorry for the lecture
Here of all places this is unnecessary. I posted the link specifically hoping someone would respond like this.
It’s true that scientists can extract clusters from genetic data that match what we call races. If you gave me a bunch of human genotypes sampled from around the world and let me fuck around with that data and run it through PCA for a few hours, I’m sure I could do the same. But it doesn’t automatically follow that my classification is correct.
If we treat the widely separated clusters as races, we don’t automatically recover a black race and a white race. We end up with a Mandenka race, a white race, and a Bantu + Yoruba race, with African-Americans smeared out between them.
If we’re discovering clusters that don’t fit with our racial preconceptions that is evidence the clusters that do match some of our racial preconceptions aren’t bullshit. Also, aren’t we looking for genetic evidence of cultural and geographical isolation? Isn’t the fact that we see different clusters for different groups in Africa just evidence that those groups have been (reproductively) isolated for a really long time? I would predict from these findings that when humans first left the continent there were already distinct groupings and that not all of these grouping had descendants that left Africa.
Also, from the chart posted here I would predict that the Africans kidnapped and purchased as slaves came more from the Yoruba and much less so from the Mandenka. They probably didn’t all come from the Yoruba, perhaps the others came from the groups in the upper right corner of this chart that you linked in your other comment. Or perhaps they didn’t come from the Yoruba but others in that corner and the Yoruba are just closely related to those other groups.
EDIT: So there were a lot of tribes that had members become slaves. Like nearly every major tribe appears to have been affected. I’m going to have to find something that tells me proportions which will take longer.
From your other comment on that chart.
The Fulani + Bulala are as far apart from some of the other African samples as they are from the Europeans!
If you go search for pictures of both you can notice the phenotype differences as well.
Here of all places this is unnecessary. I posted the link specifically hoping someone would respond like this.
Mission accomplished! :-)
If we’re discovering clusters that don’t fit with our racial preconceptions that is evidence the clusters that do match some of our racial preconceptions aren’t bullshit.
Sounds reasonable.
Also, aren’t we looking for genetic evidence of cultural and geographical isolation? Isn’t the fact that we see different clusters for different groups in Africa just evidence that those groups have been (reproductively) isolated for a really long time?
It can be, although variation along principal component axes can also represent genetic change due to migration. (I picked up on this potential confound by reading a Nature Genetics paper that made the same point from the opposite direction. That is, variation along a PC can be due to continuous geographic separation instead of migration.)
Also, from the chart posted here I would predict that the Africans kidnapped and purchased as slaves came more from the Yoruba and much less so from the Mandenka.
That’s looks about right to me. Table 1 from the paper estimating African ancestry gives a detailed breakdown of the African ancestry of the African-American sample, and it fits what you suggest.
Here of all places this is unnecessary. I posted the link specifically hoping someone would respond like this.
If we’re discovering clusters that don’t fit with our racial preconceptions that is evidence the clusters that do match some of our racial preconceptions aren’t bullshit. Also, aren’t we looking for genetic evidence of cultural and geographical isolation? Isn’t the fact that we see different clusters for different groups in Africa just evidence that those groups have been (reproductively) isolated for a really long time? I would predict from these findings that when humans first left the continent there were already distinct groupings and that not all of these grouping had descendants that left Africa.
Also, from the chart posted here I would predict that the Africans kidnapped and purchased as slaves came more from the Yoruba and much less so from the Mandenka. They probably didn’t all come from the Yoruba, perhaps the others came from the groups in the upper right corner of this chart that you linked in your other comment. Or perhaps they didn’t come from the Yoruba but others in that corner and the Yoruba are just closely related to those other groups.
EDIT: So there were a lot of tribes that had members become slaves. Like nearly every major tribe appears to have been affected. I’m going to have to find something that tells me proportions which will take longer.
From your other comment on that chart.
If you go search for pictures of both you can notice the phenotype differences as well.
I’ll maybe say more after I look at that chapter.
Mission accomplished! :-)
Sounds reasonable.
It can be, although variation along principal component axes can also represent genetic change due to migration. (I picked up on this potential confound by reading a Nature Genetics paper that made the same point from the opposite direction. That is, variation along a PC can be due to continuous geographic separation instead of migration.)
That’s looks about right to me. Table 1 from the paper estimating African ancestry gives a detailed breakdown of the African ancestry of the African-American sample, and it fits what you suggest.