Gene flow with Neanderthals exists in all modern humans

April 10, 2021 5:27 AM

That thing you heard about Africans not having Neanderthal DNA wasn't the conclusion of any studies. It was an assumption used in studies to calculate how much Neanderthal DNA was in European genomes. Now that researchers have directly compared Neanderthal and African DNA, they've found that Africans carry surprising amount of Neanderthal DNA.

The previous assumption of no Neanderthal DNA in Africans has been used by white supremacists (NYT, paywalled) to argue that Europeans and Africans did not intermix and evolved as separate races. This study (Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals, open access) "reveals higher Neanderthal ancestry in African individuals than previously seen and suggests that back-to-Africa migrations contributed to this signal."

posted by clawsoon (10 comments total)

Anyone whose spent any winter north of 60 (or north of 45 on the North American parties) will totally believe there were back Africa migrations.

Sample Neanderthal African migrant father: "We're heading south until people start questioning why we face the fur in our leathers to the inside".
posted by Mitheral at 6:56 AM on April 10, 2021 [2 favorites]

It looks like most of the analysis was done with YRI samples from the 1000 Genomes Project, which were collected among Yoruba in Ibadan, Nigeria. I see that they mention other African samples in the study, but I'm not quite smart enough to figure out what they did with them. Given that Africa has more genetic diversity than any other continent with a very complex history of migration and admixture, I feel like I shouldn't be quite so confident saying such sweeping things about "African DNA".
posted by clawsoon at 6:58 AM on April 10, 2021 [16 favorites]

Commingling is not a bad description. A lot of the interbreeding in general took place over long periods of time with groups living near or with each other. Just noting that a lot of it appears to have been consensual.
posted by xammerboy at 8:07 AM on April 10, 2021

So wait... the Nazi argument is “We’re superior to them - We’re Neanderthals?”
posted by Devils Rancher at 10:14 AM on April 10, 2021 [11 favorites]

clawsoon, thx for posting! I was getting on to make a remark about white supremacists, clinal variation of traits (i.e. races don't exist), but you beat me to it. I've moved out of human evolution so missed this. Published HERE. What is so novel compared to this 2014 work by Tishkoff?

Devils Rancher - YES!..? Its totally bizarre. Cue Wagner. But due to the fact that it looks like this is admixture through ancestral Europeans, it sounds like their milk drinking silliness won't stop anytime soon. Anti-miscegenationists... so long as its within your own species!?

An additional interesting question that could be asked is if the sex-biased admixture / weak purifying selection for X chromosome (an apparent preferred signal for neanderthal males mating with human females) and no neanderthal mitochondrial DNA in H. sapiens still holds in this other experimental population! I'm sure Harris is already thinking about it, as that was her earliest work. Would be interesting to know if anyone can tell how the genes introgressed there (from neanderthalensis "directly" or through European populations).
posted by rubatan at 10:27 AM on April 10, 2021 [6 favorites]

rubatan: What is so novel compared to this 2014 work by Tishkoff?

I'm not anything near an expert in this area, and I'm skimming the articles while my daughter pulls me around, but it looks like the newer article is using newer software which doesn't require a modern reference population, and (as a result, I'm guessing?) they're able to provide counts of Neanderthal DNA (~51Mb in the average European sample, ~17Mb in the average African sample) where the older study provided D values.

I don't even know what a D value is, so I'd be happy for someone who does know to step in and give both studies the readings they deserve.

From the article, it sounds like Tishkoff has even more data on this question that she hasn't published yet.
posted by clawsoon at 12:16 PM on April 10, 2021 [1 favorite]

rubatan: clinal variation of traits (i.e. races don't exist)

I came across this article because someone on Slashdot was voted up as "informative" for saying that races are real because of "tens of thousands of years of isolation without interbreeding". I was happy to point them to the FPP article, one of the classics on clinal variation, and maps of sickle cell, blood type and lactase persistence which show admixture and overlapping clinal variations which are all different and don't follow any "racial" lines.

I can tell that I made a difference because they called me a "a virtue signalling misinformed ignorant person" in response to the data, lol.
posted by clawsoon at 12:25 PM on April 10, 2021 [18 favorites]

"Studies had suggested East Asians have 20% more Neanderthal DNA than Europeans...By suggesting that Europeans introduced Neanderthal sequences into Africa, the new study points to an explanation: Researchers previously assumed that Neanderthal sequences shared by Europeans and Africans were modern and subtracted them out. After correcting for that bias, the new study found similar amounts of Neanderthal DNA in Europeans and Asians—51 and 55 Mb, respectively."

So much has been learned or rewritten in the past ten to fifteen years about near human relatives interbreeding it's difficult to keep track of it all. It will be nice when it's all compiled in book form instead of this steady drip of information.
posted by ockmockbock at 2:40 PM on April 10, 2021 [6 favorites]

Given that Africa has more genetic diversity than any other continent with a very complex history of migration and admixture, I feel like I shouldn't be quite so confident saying such sweeping things about "African DNA".

I've always loved this particular chart, from a Current Biology paper. Diversity of the human race? Well, actually, outside of Africa, we are all fairly closely related clades of just one tiny branch of the human genetic tree. There are groups living within a few miles of each other in Africa that have more genetic difference than a Norwegian does from a native Australian.
posted by tavella at 10:20 PM on April 10, 2021 [8 favorites]

Ibadan! That's my home town. Don't think I've ever seen it mentioned before on a Western general interest site.
posted by glasseyes at 1:43 PM on April 11, 2021 [2 favorites]