Thursday, September 17, 2015

Ancient North Eurasian

Ancient North Eurasian is an ancestral component now somewhat common in population genetics... It was originally discovered through the genome of a Siberian boy who died over 20,000 years ago referred to as either Mal'ta boy or MA-1 and was backed up as being a real entity in pre-historic Eurasia through other ancient genomes like that of Afontova Gora-2. [1]


It's discovery really shook up a lot of things like our understanding of the origins of Europeans, Native Americans and even groups such as Central Asians, South Asians and various West Asians who seem to carry either Ancient North Eurasian or Ancient North Eurasian-related ancestry.

Lazaridis et al. 2013-2014 seemed to suggest that Europeans were basally a three-way mixture between Ancient North Eurasians / MA-1 related peoples, what they dubbed Western European Hunter-Gatherers based on the ancient genomes of various Mesolithic Hunter-Gatherers from Europe like Loschbour and then finally Early European Farmers who began entering Europe around the Neolithic from West Asia. 

Since then that model's become rather obsolete and has been replaced by one where all of the supposed Ancient North Eurasian ancestry in Europe is owed to the spread of the Indo-European languages by pastoralist peoples from the Pontic-Caspian Steppe. 




These pastoralists were carrying with them a foray of different ancestries from what looks to be Caucasian-like ancestry rich in what looks to be Ancient North Eurasian-related & West Asian ancestry and what is for now referred to by chaps like Wolfgang Haak of Haak et al. 2015 as "Eastern European Hunter-Gatherers (EHGs)". [2] 

EHGs almost fit as a mixture between Ancient North Eurasians & Western European Hunter-Gatherers but instead don't entirely look to be the result of such a mixture. Though as David Wesolowski who runs the Eurogenes genome blog and ancestry project once remarked in the quote below- :

"It depends how you define EHG, ANE and WHG, and the concept of pure components.
They can all be distinct pops, or EHG can be a mix of ANE and WHG, or even WHG can be a mix of EHG and something as yet unsampled."

-it's honestly rather iffy and tricky modeling these pre-historic groups with wildly different time stamps on them (Mesolithic for WHGs and EHGs and Paleolithic for ANEs) as mixtures of one another.

But David seems to assume groups like EHGs and WHGs are likely a mixture between groups that preceded them perhaps like Ancient North Eurasians and some other groups as yet unsampled. The cold hard truth of the matter is that we require more samples of pre-historic Hunter-Gatherer groups across West Eurasia to really understand what EHG and WHG are and how exactly they're connected to ANE because the current models seem inadequate.

 It could just be that Eastern European Hunter-Gatherers are somehow extra related to Ancient North Eurasians or somehow partially descended from them and something Western European Hunter-Gatherer related. We'd need more ancient genomes across time and space in Europe and other parts of Eurasia to truly grasp this with any kind of conclusive detail.

Early Neolithic = Early European Farmer


Although one thing is resolved for now... A group of "pure" Ancient North Eurasians didn't come and contribute Ancient North Eurasian ancestry to the ancestors of modern Europeans; this Ancient North Eurasian-related ancestry is ultimately owed to expansions from the Steppe. Whether EHGs are "WHG + ANE" or related to MA-1 in some other way or not.

Though it is worth-noting that the non-EHG and "Caucasian-like" ancestry in Pontic Caspian Steppe pastoralists like the Yamnaya did also carry Ancient North Eurasian-related ancestry and in this case; not seemingly owed to Eastern European Hunter-Gatherer ancestry. 


The redder a place or its "outline" is; the richer in ANE-related ancestry it is
In the end though what looks to be Ancient North Eurasian ancestry or Ancient North Eurasian-related like EHG ancestry is found all over Eurasia from Siberia to South Asia or Western Europe to Central Asia. In a modern context it tends to peak in Siberian groups like Kets [3] or various modern South Asians and in West Eurasia peaks in the Caucasus region.

It also really helped redefine our understanding of the origins of Native Americans who like many populations on this planet are now understood not to be some "pure" separate branch of the Homo Sapien Sapien family tree but a mixture of sorts like Europeans. In their case the mixture seems to be between Ancient North Eurasians and East Asian-related ancestry. [4]




If I had to quickly dive into where the component stands in Eurasia; it's essentially closest to Eastern & Western European Hunter-Gatherer and seems to share as geneticists suggest; a sort of earlier root with these components like it does with Western European Hunter-Gatherer in that Lazaridis et al. 2013 diagram I shared.

Though as I said; we really need more samples from across Eurasia (West Eurasia, Siberia, Central Asia, South Asia etc.) from various time periods to really understand the true nature of groups like Ancient North Eurasians, Western European Hunter-Gatherers and Eastern European Hunter-Gatherers because as it stands; things stand on somewhat unsure and confused ground.

For all we know; what looks to be non-Steppe derived "ANE" ancestry in groups like South Asians, Central Asians and West Asians may not be owed to some sort of "pure" Ancient North Eurasian group like we once thought was the case for Europeans...

It could instead mean that these groups owe their Ancient North Eurasian-related ancestry to Eurasian Hunter-Gatherer groups somehow related to Ancient North Eurasians or who carry ANE ancestry themselves in some way or other; more ancient DNA analysis is needed... I say this a lot and before this blog post is over will say it again because it can't be emphasized enough.

This uncertainty I highlighted above is essentially why I insist on sometimes writing "Ancient North Eurasian-related ancestry" rather than undoubtedly assuming some of these non-European populations have direct ANE ancestry.


Eurasia


Nevertheless, for the time being what we dub "Ancient North Eurasian" is highly divergent from Western European Hunter-Gatherers despite the seemingly closer relations between ANEs and European Hunter-Gatherers when compared to Eastern Non-African groups, to a point where Native Americans will often seem more similar or closer to Mal'ta boy than Europeans are like in analyses such as IBS:


MA-1 IBS


This being the case despite the fact that the East Asian-related ancestry that makes up the rest of Native Americans' ancestry is less related to Ancient North Eurasians like Mal'ta boy / MA-1 than the European Hunter-Gatherer ancestry in Europeans is, though Europeans might be shifted away a bit by the highly divergent Basal Eurasian component in their West Asian / Near Eastern-related ancestry.


Eurogenes K=8 is a good representation of the levels of Ancient North Eurasian-related ancestry found across various global populations


Nevertheless, ANE is a pretty distinct ancestral cluster of its own with what seems to be a very large spread across Eurasia of either ANE or ANE-related ancestry showing up in small amounts even in some East Asian populations as well as somewhat in Egyptians, a Northeast African population.

Reference List:






Notes:

1. What shows up as Ancient North Eurasian in East African groups like the Gumuz or Anuaks in the K=8 admixture analysis isn't actually ANE ancestry. From what David once told me; it's essentially some sort of archaic Eurasian element these groups demonstrate that just won't fit into the runs other clusters/components. 

These East African cluster rich groups in my experience do tend to show an odd as of yet unexplained very small Eurasian / Out-of-Africa (related to Non-African populations) element in various runs especially at K=2; just don't make much of it for the time being. 

2. I've put a little time into formally explaining components like Ancient North Eurasian or the Near Eastern / West Asian ancestry (Early Neolithic Farmer) in Early European Farmers because many I've encountered who've just gotten recently interested in population genetics sometimes might need a more straightforward explanation for what these components are / what we for now understand of them without having more ancient samples to paint a better picture so here are your explanations.

3. The world map that shows various ANE levels across the globe via the colors green and red is owed to a chap David/the author Eurogenes refers to as Sergey as mentioned here. And the MA-1 IBS spreadsheet if you're wondering is owed to David.

4. This is a direct note quoted from David/ the author Eurogenes I'm sharing because it's rather interesting: [-]

ASI = Ancestral South Indian, you can learn a little about it here. It's essentially a "South Indian" centered Andamanese & perhaps also Australo-Melanesian related component though we'll need ancient DNA from South Asia to really grasp it as for now it's not even "purely" made up of such ancestry and as David notes; is "mixed" in that it carries ancestry like Ancient North Eurasian-related ancestry. That's because all the models of it we have for now are based on modern South Asians who are all mostly a mixture between West Asian-related, ANE-related, Pontic Caspian Steppe-derived & "ASI" ancestry.  The only way to get a good and unmixed edition of it would be sufficient ancient DNA from South Asia where it can be found in such a state. 


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