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Wednesday, July 3, 2013

New and improved Ancestry Finder results


I just noticed a significant shift in my Ancestry Finder (AF) results, and many users can probably expect to see something similar, if they haven't already. No doubt, this is a due to the recently completed transition at 23andMe from Build 36 to Build 37 coordinates (see here), and also the company's burgeoning client database. It seems like a change for the better, at least in my case, because the new results appear to show greater accuracy and more detail.

My "Countries of Ancestry" list at the 5cM/4 grandparents setting (the one I find most useful) makes a lot of sense considering that the vast majority of my ancestors from within the past 500 years probably came from Poland and surrounds. The UK's position in 4th place, with a score of 0.8%, is surprising, but I suspect that's due to the over-representation of samples from that country in the 23andMe database. In part it might also be the result of Scottish emigration to Poland (see here).

Poland 4%
Russia 1.5%
Germany 1%
UK 0.8%
Hungary 0.8%
Romania 0.7%
Ukraine 0.5%
Lithuania 0.4%
Ireland 0.4%
Czech Republic 0.4%
Austria 0.4%
Sweden 0.3%
Serbia 0.3%
Greece 0.3%
France 0.3%
Finland 0.3%
Denmark 0.3%
Norway 0.2%
Latvia 0.2%
Iceland 0.2%
Croatia 0.2%
Bulgaria 0.2%
Belgium 0.2%
Belarus 0.2%
Switzerland 0.1%
Slovenia 0.1%
Slovakia 0.1%
Netherlands 0.1%
Macedonia 0.1%
Italy 0.1%
Estonia 0.1%
Albania 0.1%

However, one of the main shortcomings of this tool is that it doesn't give any explicit information about the direction of gene flow. So in theory, it's possible that all of the potentially foreign segments highlighted by the AF across my genome, like those shown below, are a legacy of population movements from Poland.



Actually, it's even more complex than that, because, for instance, some of my Russian hits are from people who have German surnames listed in their profiles. In fact, at least one of them appears to be entirely of Volga German descent. So it might well be that most of the segments I share with Germans are of Polish origin, but some of the segments I share with Russians are of German origin.

I can't think of a way around these problems. But it might be useful to cross check the AF results with those from other ancestry tools, like the 23andMe Ancestry Composition or the GEDmatch chromosome paintings, to try and spot correlations and get a rough idea about the biogeographic origins of the segments. Sadly, my Ancestry Composition is still useless because I'm clearly overfitted, like many other clients (see here), so forget that idea if you're in the same situation.

Another thing that might help is checking if the supposedly foreign hits belong to clusters of segments shared with people from the same or similar countries. For instance, I have one such cluster on the centromere (break point) of chromosome two, where I share several segments with people of Northwestern European origin. Some of these matches are shown below.




There's no way of knowing whether these hits derive from the same haplotype, but assuming they do, then it's an intriguing result, because as far as I know there wasn't any Polish emigration to Iceland or Ireland until very recently. Also, I'm not aware of any Icelandic or Irish emigration to Poland. However, I do know that Scandinavian Vikings traveled to all of these places (see map below). So perhaps this is a segment of Scandinavian origin that made its way to Poland during the Viking Age?


Then again, it might be a haplotype that is relatively common across Northwestern Europe as a result of positive selection, and actually a composite of smaller segments from both sides of my family. In other words, perhaps the AF algorithm has mistaken Identical-by-State (IBS) for Identity-by-Descent (IBD)? I might never be able to get to the bottom of that, but it's fun to speculate about different scenarios.

For more info about the AF and the caveats that apply when using it to disambiguate your local ancestry, please refer to my blog entry about its impeding public release three years ago...


"Ancestry Finder" tool coming soon at 23andMe

2 comments:

Colin Welling said...

Belgium, I knew it!!!

Richard Robbins said...

Looking at my AF results at 5cM, with 1+ Grandparents coming from same country (Poland)

Poland 3.0%–5.3%
United Kingdom 1.6%–3.9%
Russia 1.4%–3.1%
Germany 1.1%–4.1%
Ireland 0.5%–1.6%
Netherlands 0.5%–1.2%
Ukraine 0.4%–2.1%
Lithuania 0.4%–1.4%
France 0.4%–0.7%
Croatia 0.4%–0.5%
Hungary 0.3%–0.9%
Norway 0.3%–0.6%
Spain 0.3%–0.4%
Finland 0.3%–0.4%
Denmark 0.2%–1.1%
Czech Republic 0.2%–1.0%
Sweden 0.2%–0.7%
Switzerland 0.2%–0.5%
Iran 0.2%
Serbia 0.1%–0.4%
Colombia 0.1%–0.3%
Estonia 0.1%–0.1%
Moldova 0.1%
Mexico 0.1%

In other words, no surprises here.