keskiviikko 16. marraskuuta 2016

Ancient admixtures look shifty

It is hard to believe in some ancestry results.   FamilyTreeDna's new Ancient Origins give me following results

Metal Age Invader 12%
Farmer 30%
Hunter-Gatherer 54%
Non-European 4%

Regarding Metal Age Invaders they refer to the Metal Age Yamnaya culture, regarding Farmers to the Neolithic Anatolian migration to Europe and regarding Hunter-Gatherers to ancient LaBrana, Loschbour and Motala samples.   Regarding non-European proportion they give a hint to look at myOrigins, which is FamilyTreeDna's admixture analysis based on present-day populations.  My myOrigins give me only one non-European group, Middle Easterners.  I doubt it, the non-European in my Ancient Origins test is likely Asian.

Going further in analyzing results I compared my Ancient Origin results to  scientific papers,  Haak et al. 2015 giving comparable results.  Haak et al.  gives following results for Finns:

EN (Farmers) 31.5%
Nganasan (Asian) 10.2%
WHG (Hunter-Gatherer) 7.9%
Yamnaya (Metal Age Intrurers) 50.4%

Respectively Norwegians get in this study
 
EN (Farmers) 48.2%
Nganasan (Asian) 4.2%
WHG (Hunter-Gatherer) 0%
Yamnaya (Metal Age Intrurers) 47.5%

We can see a huge transition between Yamnayas/Iron Age Intruders and Hunter-Gatherers between Ancient Origins and Haak et al.  I know something about the method used by Haak et al., but I have no idea what FamilyTreeDna did. However, if I try to guess, I would say that they could have used a very drastic LD-pruning.  I can get similar differences by heavily pruned data and it makes sense.  Metal-Age invasion to Europe happened during the Bronze Age, thousands years later than the arrival of hunter-gatherers.  So it is reasonable to assume that we have still much more Bronze Age genetic drift than drift from hunter-gatherers, thus removing LD removes more ancestry of Metal Age Intrurers.  Pruning present-day samples does't have same effect due to more similar genetic composition.

I made also some admixture tests.   Pruning LD gives a big change in ancient admixtures.

My result without pruning

Anatolian_Neolithic 31.4
BA_East_European_Steppe 44,8
East_and_Southeast_Asian 10,8
Western_Hunter_Gathrerer 13

and after pruning


Anatolian_Neolithic 27.5
BA_East_European_Steppe 25.9
East_and_Southeast_Asian 7.8
Western_Hunter_Gathrerer  38.8

I am not saying that the difference between results of FamilyTreeDna and Haak et al. is caused by pruning, because I don't know it.  I only state that pruning ancient samples is risky.




3 kommenttia:

  1. I wonder that the Asian component in Finns/Norwegians is of Nganasan and not Nenets origin, as the latter settle much closer to scandinavia.

    VastaaPoista
  2. It is much older than Nganasans or Nenets for sure. If we use ancient genomes as a reference it exists everywhere in Northern and Central Europe. If we use modern genomes as a reference the zero level is fixed to the lowest level, but it doesn't mark an absolute zero level.

    VastaaPoista
  3. It's probably from Bronze Age Arctic "Ymyakhtakh" culture represented by Bol'shoy Oleniy Ostrov.

    "We might suggest that the Bol’shoy Oleniy Ostrov people represented a small
    immigrant group; however this disagrees with the fact that archaeological finds
    from that cemetery show no typological differences from those coming from
    other cemeteries and camps across the entire sea coast of Lappland. Possibly the
    ancient Lapplanders were representatives of one of the earliest populations, who
    had migrated to the north and east of Eurasian Arctic in
    the early Holocene. "

    mtDNA of these people was a lot more eastern than that of Saamis who replaced them (and in turn were replaced by Scandinavians and Finns), and that should be the case on genomewide level as well.

    http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1003296

    VastaaPoista

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