Mathiesen talk on selection in Europe at Brown University conference

Angela

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As Reich was one of the speakers in Session 1, Mathiesen, now at U Penn, spoke during Session 2.

(For Reich, see:

I'm just going to post a few notes I made, and then screenshots of some of his posters, which are pretty self-explanatory, but certainly flesh out what was in his earlier paper.

Lactase persistence is the strongest signal of selection but not selected for until long after the start of cattle domestication
Fads gene is involved with diets heavy in marine/animal fat metabolism versus plant metabolism depending on whether it’s turned on or off.
Again, it’s not selected for until long after the change to plant, i.e. cereal eating (1000 BC)). Why? He just says maybe change in environment. At least that’s what I got out of it. He speaks extremely quickly, and it’s hard to keep up. This is what effects cholesterol levels
Amylase, which helps to break down starch, is not under selection, although they thought it would be.

Blood groups-affects disease susceptibility. O type blood carriers have more resistance to cholera. The hunter-gatherers carried more O than any modern European population.

Skin pigmentation is very difficult to predict because there are many traits working together. However, he does provide a cleaned up chart showing the percentages in the various ancient groups and comparing them to modern Europeans.

See:
https://brown.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=e01fc0e4-de79-43bc-8384-aa0700f62645

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Lactase persistence is the strongest signal of selection but not selected for until long after the start of cattle domestication

Mare milk ??

From Wiki French (for once more detailed than the English article) :

"Le lait de jument est le lait que produit la jument pour nourrir son poulain durant les six premiers mois suivant la naissance, à raison d'une douzaine de litres par jour. Il contient beaucoup de lactose, peu de lipides et une bonne quantité de vitamine C.

Consommé par les humains depuis la Préhistoire, le lait de jument est apprécié depuis des siècles par les Mongols, les habitants de l'Asie centrale et des steppes indo-européennes, notamment sous forme de la boisson fermentée kumiz, et de kéfir. Beaucoup moins consommé dans les pays occidentaux que le lait de vache, le lait de jument suscite pourtant un engouement depuis les années 2000 pour ses qualités nutritionnelles et sa composition assez proche du lait maternel humain."

The gist :

- A mare produces about 12 liters a day.
- Mare milk is rich in lactose and vitamin C, poor in lipids.
- Consumed by men since prehistorical times, notoriously by Mongols and Eurasian Steppe dwellers. (Found on Botai culture pottery)
- Close to human milk. (Because horses are not ruminants)

"Le lait de jument est particulièrement associé aux Mongols, chez qui il occupe « une place de premier ordre », étant réputé notamment pour « blanchir » la peau et les organes internes. C'est un breuvage quasiment sacré. Il est d'usage de baigner les bébés dans le lait de jument fermenté pour les renforcer, et de leur en faire consommer dès l'âge de huit mois."

- Particularly associated with and popular among the Mongols, where it is believed to whiten the skin.
- Almost considered a sacred beverage.
- Babies are bathed in mare milk to strengthen them.
- Babies are made to drink mare milk from the age of 8 months.
 
Mongols and Central Asian people consume mare's milk, but they don't carry the lactase persistence gene.
 
Mongols and Central Asian people consume mare's milk, but they don't carry the lactase persistence gene.

Seems to settle the question...
 
Am I reading the first chart right? Saami as 100 % steppe? That does not seem to fit with my understanding of what "steppe" is ? I would have expected a mix between something more Eastern and hunter-gatherer.
 
Am I reading the first chart right? Saami as 100 % steppe? That does not seem to fit with my understanding of what "steppe" is ? I would have expected a mix between something more Eastern and hunter-gatherer.

I thought that was strange as well.

The Saami do have some Anatolian farmer, so that's going to throw those percentages off, and they also have quite a bit of Siberian like ancestry.

Imo, modern populations shouldn't be used as standins for ancient ones. It would be like using the Sardinians for the EEF. They might be close, but they're not identical.

I also think it's slightly misleading putting the Lazaridis and Haak papers there, because that isn't how they did the admixture at all.
 
Am I reading the first chart right? Saami as 100 % steppe? That does not seem to fit with my understanding of what "steppe" is ? I would have expected a mix between something more Eastern and hunter-gatherer.

what is wrong with it? if they like to put hunter gathers from the paleolithic with Yamnayans from Chalcolithic with a good chunk of EHG... well, what to say, people like to be herded by politics or by scientists.
 
Am I reading the first chart right? Saami as 100 % steppe? That does not seem to fit with my understanding of what "steppe" is ? I would have expected a mix between something more Eastern and hunter-gatherer.

Indeed, 100% steppe for Saami does sound strange.

Here's an admixture chart from another paper, which shows the various other components:

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https://www.nature.com/articles/s41467-018-07483-5

As Angela said, there is some farmer ancestry in Saami; as well as a critical mass of "Nganasan".
 
it is very interesting but i dont believe it

If you're not interested in genetics and science, why are you on a site dedicated to them?
 
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If I rely on this, concerning pigmentation, I could say, roughly:
- this blue eyes mutation was at first a (maybe) Paleo one, of western HG's pops, and reached northern pops, perhaps associated with post-Magdalenian moves? No direct explanation for me -
- the first skin mutation (SLC24A5) seems linked rather to eastern pops, HG or Neol, and the second (SLC45A2) seems linked rather to north-eastern HG's pops - ? it's like western HG had lived a long time under rather smooth climates before reaching North when the other had known since a long time cold or mountain climates??? (this last interrogation is a bit aventurous)
 
If I rely on this, concerning pigmentation, I could say, roughly:
- this blue eyes mutation was at first a (maybe) Paleo one, of western HG's pops, and reached northern pops, perhaps associated with post-Magdalenian moves? No direct explanation for me -
- the first skin mutation (SLC24A5) seems linked rather to eastern pops, HG or Neol, and the second (SLC45A2) seems linked rather to north-eastern HG's pops - ? it's like western HG had lived a long time under rather smooth climates before reaching North when the other had known since a long time cold or mountain climates??? (this last interrogation is a bit aventurous)

That's what it seems like to me as well, although I doubt we'll ever really know.
 
Was there anything in the paper about Rh negativity and where it originated?


[FONT=&quot] .........[/FONT][FONT=&quot]On the other hand, no obvious selective advantage is known, there are [/FONT]no obvious genomic signals of selection[FONT=&quot] on the Rh- allele, and if there were a selective advantage to the Rh- allele then we might ask why [/FONT]it[FONT=&quot] hasn’t fixed, since once the Rh- frequency rose above 50%, it would be selected for, rather than against. So this only really works if it is overdominant. Another possible explanation is reproductive overcompensation - Rh- women have more children to replace the ones that die for haemolytic disease. But this seems unlikely. The range of parameters for which this model works is [/FONT]relatively small[FONT=&quot], particularly since the effect gets worse for subsequent pregnancies. A third explanation, suggested by [/FONT]Haldane in 1942[FONT=&quot] is that the high frequency in Europe is due to the fact that present-day Europeans are recently admixed between a population that has a very high frequency of the Rh- allele and one that a very low frequency. In fact, the ancient DNA evidence suggests that something like this is close to the truth. [/FONT]Cavalli-Sforza and colleagues[FONT=&quot] thought that this was specifically a mixture between Rh- hunter-gatherers and Rh+ Farmers, largely based on the observation that the Basque population, who they believed to have largely hunter-gatherer ancestry, have a very high frequency of the Rh- phenotype............[/FONT][FONT=&quot].....................The Rh- allele seems to be relatively common in hunter-gatherers and, particularly, in steppe populations, and relatively rare in early farmers, partly confirming Haldane and Cavalli-Sforza’s hypotheses.........[/FONT]
http://mathii.github.io/2017/09/21/blood-groups-in-ancient-europe
 
In a way, it was good that drecfg reignited this thread, as I missed it before.

The evidence about the lactase persistence gene is particularly interesting, and I wonder about the geographic locations of its samples.

It would seem to indicate a major expansion commencing with the Atlantic Bronze Age, when there appear to have been migrations from Northern Iberia (where lactase persistence did not confer a huge advantage) to the North West Atlantic (where it did).

As I understand it, the same gene also probably flourished in another Northern location - the North Western Steppe, from which it then spread into Srubnaya and Northern India.

My guess is that the gene probably originated in Southern/Central Europe and only really thrived when it spread into Northern areas where calcium deficiency might have been common.
 

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