Why do black pupils in the US underachieve academically when one factors out poverty?

Great Debates
621

In simplified terms, yes.

The broad consensus (look at the diagram in your own most recent cite from Ms Brahic) is that out of africa occurred in a roughly one-way direction about 65 kya. Minimal contact between sub-saharan and non-africa lines for about 60,000 years. Non-african pools acquire Neanderthal introgression for most of their lineages because of when it occurred (near the out of africa migration, and before most subsequent splits).

Per Reich, at least, semitic genetic pools back to east africa 3kya; some subset of that into southern africa 1.5kya.

But you can go read about all this for yourself, if it’s news to you.

It’s why the out of africa gate creates two broad pools. There are plenty of interesting exceptions and nuances, which is why the idea of calling a given genetic pool a “race” doesn’t make much sense. There is plenty of diversity in both these pools, which is why trying to divide by quantity of diversity makes no sense at all.

What there is not, is passing of genetic information on any scale large enough to homogenize between the non-african, and sub-saharan pools. So introgressed gene variants (Neanderthal and Denisovan, e.g.) and ordinary new SNP variants that are selected for by evolution (1.6% of the Perelegen SNP database representing 1,800 genes across human physiology, per Eric Wang) remain for the most part of each side of that Red Sea-Sahara gate, passing only to descendant non-african or subs-saharan lines, depending on which pool got the gene variants. And within those two broad pools, how penetrated the variant is will depend on how early it showed up, and how reproductively advantageous it was (or, in some circumstances, whether it was in a founder group or present at a migration bottleneck).

Neanderthal genes are an example. Average frequency for gene variants in prostate cancer are an example. MCPH1 haplogroup D is an example. Genes driving bone density, creatine kinase levels, and plenty of others are more examples.

It isn’t that there is a perfect division of gene variants. It’s that there’s enough of an average frequency difference for gene variants that drive phenotypic outcomes to create two different pools.

Of course, there’s always the confounder of nurturing influences. Why, I was noticing just yesterday at one of the college basketball games that blacks get nurturing for basketball, and whites get nurturing for watching it. I was sad that all those young kids–overwhelmingly european–in the rows right behind their basketball stars were too lazy to go actually become those stars. Or maybe they’d rather study in their off hours than become basketball stars. :smiley:

Seriously, though, I really encourage you to read the original papers and pay less attention to what is massaged into a headline for consumption by the masses. I think you’ll find the statement I’ve quoted from you above is roughly the consensus…(east africa and the sub-saharan Sahel being the exceptions and not the rule).

622

Were you going to make a correction around your earlier comments wrt what the Reich data actually says about how much Neanderthal DNA made it’s way into southern africa.

As a generous percentage, the correct amount would be on the order of less than 5% of the amount in eurasian lines, and then only for those select groups the paper calls out–not a broad distribution among the rest of the sub-saharan lines outside of east and southern africa.

623

A sample paper on Neanderthal admixture in non africans.
"…Of these, haplotype B006 is structurally distinct; with
only four derived alleles it is the closest to the ancestral one. Common outside Africa and
virtually absent in sub-Saharan-Africa (Figure 1)…
This provides additional verification of the findings by (Green et al.
2010) that Neandertals contributed to the genetic makeup of modern human populations outside
Africa. Our data indicate that Neandertal admixture occurred very early or prior to their
worldwide expansion…" e.g.

Stephen Oppenheimer on the possible routes out of africa.

A lay article outlining the basic idea of the out of africa migration.
Splashy and typically oversimplified headline:
*“The entire human race outside Africa owes its existence to the survival of a single tribe of around 200 people who crossed the Red Sea 70,000 years ago, scientists have discovered.”
*

Oppenheimer quote in the above writeup:
“What you can see from the DNA of all non Africans is that they all belong to one tiny African branch that came across the Red Sea.
If it was easy to get out of Africa we would have seen multiple African lineages in the DNA of non-Africans but that there was only one successful exit suggests it must have been very tough to get out. It was much drier and colder then.”

The happy little quote at the end antedates the publication of Neanderthal introgression, apparently:
“I think we should all be happy with that, as afterall, it means that people from all over the world are not all that different from each other.”

But in any case, that sort of quote needs to come with the caveat that what is meant is that we all had the same ancestor if we go back far enough. (Even me and my sisters, who are very different genetically from me.) Nothing to do with average differences derived from diverged pools, though.

624

So which two neighboring villages are the cut-off? Which two villages are next to each other but share very little genetic ancestry?

625

Were you going to address the demolition of your earlier cite? I’ll reply to this after you do to that, not before, thanks.

Oh, and by the way, I think it’s disingenuous to talk about Neanderthal DNA introgression as though it were settled science and there were no alternative theories for the similar DNA markers…

626

Coming from someone as expert in the massaged partial quote and convenient ellipses as yourself, that’s really quite rich.

627

Human migrations antedate villages, but if you are wondering where the cutoff is, read the cites I’ve given you.

After the out of africa migration 65 kya, there was almost no exchange for 60,000 years w/ groups left behind (groups currently termed “sub-saharan” by population geneticists. It’s thought one of the main reasons is the closing of the geographic gate, and the exact explanations are lost in time. Perhaps climate change changed sea levels. Perhaps the few hundred who got out were already far from home.

It’s much easier to track what happened than know why.

We can (and have) tracked the lineages which descended from that L3/M-N split, and I would suggest Oppenheimer’s Out of Eden as a good starting place to understand why we believe this was a splitting point with very minimal subsequent mixing until 3kya.

Somewhere after out of africa and around the time of the M-N split 45kya-ish years ago, humans mated with Neanderthals. In those 20k years gene variants arose, perhaps related to that and perhaps not. Of the Neanderthal genome, 20% or so is thought to still survive within most out of africa populations; typically 1-4% of non-africa populations. Some very early groups may have missed the Neanderthal introgression and traveled along the coast of India all the way to Australia. I believe that work is still being done.

But overall, the “two villages” you are looking for are on either side of the Red Sea 65,000 years ago, perhaps near the Gate of Grief (based on a projected coalescence point of non-africa DNA lineages).

628

So far, it looks like you are swimming upstream if you want to suggest Neanderthal DNA introgression did not occur around the time of the L3/M-N split out of africa into the non-africa lines. Whether it did or not does not change the fundamental acceptance that the out of africa lines were separated from the sub-sahara lines for most of the past 65,000 years. This is not the only splitting point one can create.

It is, however, a very broad one, and it is one into which self-identification of “black” in modern populations groups into the notion of “sub-saharan” and “non-african” in terms of average gene pools. As in, “MCPH1 haplogroup D is widely penetrated into non-african groups, but not into sub-saharan groups.”

629

This disregards the clinal relationship between villages up and down the coasts of the Red Sea, and across the Sinai into the Levant. But such a non-close, non-clinal relationship across (most probably, I assume) the southern point of the Red Sea between Djibouti and Yemen would be relatively easy to prove, one would think – your links don’t speak in such specific terms.

From what I can gather from the intertubes, ethnic groups of the area (on the African side) like Somalis are more closely related to Northern and NE Africans like Berbers and Middle Eastern populations like Arabs than more southern and western African groups.

630

It’s not “swimming upstream” to acknowledge there are alternative explanations

That’s an interesting use of “black” that somehow excludes austronesians, negritos and melaneseians…but includes the decidely non-black KhoiSan.

Yes, keep emphasising those single SNP differences, I’m sure they’ll add up to a significant percentage any day now.

631

Even in your studies (based on modeling and not direct observation), 1-4% of SNPs of sub-saharan v non-african are Neanderthal variants which are different in the non-africa pool. Remember that the idea eurasian Neanderthal gene variants are not introgressed at out of africa, but are instead remnants of more ancient common ancestry in-africa still accepts the observation that those gene variants are in one pool and not the other. The idea is that the population structure within africa left an out of africa group that carried those gene variants with them when they exited, leaving behind sub-saharan populations who did not have the Neanderthal variants.

This idea is a tough sell, and you are swimming upstream with it. It’s not the consensus, but of course in science not only do theories die hard; sometimes new theories are wrong. So you might be right.

You won’t be right if you reject the idea that a very small group of humans exited africa 65,000 years ago, and were largely separated from the residual sub-saharan groups for 60,000 years, forming two broad pools separated by a geographic migration gate. With the exception of some early split offs that made it to australia along that coastal route, modern non-africans are a separated pool from modern sub-saharans by those 60,000 years of evolutionary change. In east africa, and with a sub sub group into southern africa, we see some exceptions for which I have given you the research numbers for estimates of admixture. That admixture is nowhere near enough, or penetrated enough, to make the two pools as similar as they would be on average if they had not been separated at out of africa.

That’s why population geneticists use “sub-saharan” and “non-african” when talking about these two pools. They are two quite different average pools for gene variant frequency.

There is a great deal of research looking at Neanderthal genes and what they brought to the table, as well as when they must have been introgressed. I suggest you look into it further.

632

I’m not sure what your obsession with “clinal relationship between villages” is, but the division we are talking about is the sub-saharan pool as an average group, and the non-africa pool as an average group.

Those two groups have pools which are separated by 60,000 years. The non-africa pool contains 1-4% of Neanderthal gene variants. 3,000 years ago a semitic population made it back to east africa, so if we look at modern populations there, we’ll see introgression of non-africa genes into the sub-saharan groups. In turn, addtional migrations over the last 3,000 years would have carried some of those genes into other populations of sub-saharan africa.

But not nearly enough to efface 60,000 years of separation. Not nearly enough to homogenize those separated pools into pools which do not have average frequency differences.

Even in modern times, when we have villages, it is not the case that every juxtaposed settlement is on a contiguous genetic flow with every other settlement. Sure, admixture happens, but unless you have the same antecedent coalescent point for a founding population, even adjacent “villages” stay remarkably distinct due to factors involving culture, language, defense of territory and so on.

You aren’t going to get Romeo and Juliet to erase those boundaries so smoothly in 3,000 years such that a point group in east africa makes the entire sub-saharan population contain the same average frequency of gene variants as the non-africa average frequency.

633

Post #616, mate, I’m not going to type all that out again.

634

Post 617 should help clear up your confusion, using your own cite and the research paper underpinning your notion that the sub-saharan gene pool has somehow been homogenized by out of africa groups bringing non-africa genes back to sub-saharan groups.

Table 1, page 5 in David Reich’s paper will help you process the breathless headline and wordsmithing a little better, I think.

As always, I recommend more reading.
An additional recommendation would be to focus on the original papers and not too much on wordsmithing by reporters like Catherine Brahic.

635

So Somalis are on the ‘Asian side’ of this 60,000 year split (being that they are closer to North African and Arab populations than various other SSA groups), while near and neighboring groups in places like Tanzania and Central Africa are on the African side? I don’t think I buy that.

Enlighten me – which groups are on the Asian side of this 60,000 year split, and which are on the African side: Somalis, Khoi-San, Dinka, Haddad, Lou, Hutu, Tutsi, Berber, Yemenis…?

636

No confusion - I think you’re missing the relevant parts of post #616. Especially the final paragraph.

637

Here’s that final paragraph from Post 616:

I don’t believe in races either. I just believe that the out of africa migration defined a broad division of gene pools, which population geneticists refer to as “sub-saharan” and “non-african” because…

well, because they are a broad division of gene pools. :slight_smile:

638

Remember that we are talking about average. Average. All comers.

Because of backflow of non-africa genes into eastern africa 3kya, a given sub-group may be an exception to a general rule of average genetic history.

But if you take average makeup of all sub-saharans, you can (and geneticists readily do) talk about “sub-saharan” versuse “non-african” as two different average pools.
Which is also why no amount of nurturing diddling ever gets rid of the gap in outcomes. The average for genetic frequencies is different.
And that, of course, is why average outcomes differ. :wink:

639

So which “pool” do all those groups I mentioned belong to? It sounds like you’re agreeing, now, with me and Mr. Dibble, that there are clinal relationships in that region, and not sharp differences.

Except that it does – gaps have changed by some measures, even in the tiny period of time in which there’s been efforts (paltry as they are) to erase the gaps.

Except that we have no idea which genes are responsible for high and low intelligence, much less whether they differ on a “Asian/SSA” split or between other groups.

Or it’s for other possible reasons, like various aspects of society and culture, which don’t actually conflict with experimental evidence.

640

You can take any two “average” groups and they’d be slightly different - if you took Europe + Africa, it’d be different from the rest of the world, ditto if you took America vs the rest of the world. Hell, you could take West Africa vs the rest of the world, and there’d be a much vaster difference than between SSA vs the rest of the world.

So why this particular tiny distinction? All that effort to show that somehow the Sahara and Red Sea are such an absolute barrier in a way, say, the Bering Strait or Indian Ocean just never were. Or that the clines we see, clear as day, between SSA and OoA poulations in the Horn, East Africa, the Levant and Arabia just are an optical illusion.

You consciously pick the “average” gene pools you choose to use. Chief Pedant chooses to use one that just happens to line up with that used by racists. But that’s OK, because he says he doesn’t believe in biological races. He just believes in dividing people into groups along genetic lines :smack: