Tag Archive | Ancestry Compostion

Norwegian or English? DNA ancestry predictions

My third cousin Irene (found with DNA) complained to me via email that her ethnicity results at 23andMe were very different from Ancestry; what was going on? Irene’s recent ancestry is known to be half Norwegian (my side) and half Scottish with some Irish (about 6% expected) mixed in.

Ancestry’s predictions are on the left, 23andMe’s estimates are on the right

So I looked and saw that 23andMe (above right) has a very low estimate for Scandinavian for her, while the British and Irish (her Scottish) is fine. Ancestry DNA (above left) has the Scandinavian predicted correctly but calls her Scottish both Irish and Western European. At least it includes her in a Scots genetic community which is correct and very cool.

Family Tree DNA’s predictions

Since I had also uploaded her DNA results to Family Tree DNA, I checked there and saw that they correctly predicted 49% Scandinavian. However the Scottish shows as 36% British Isles followed by some traces including 9% East Europe? No one else saw that!

One of the problems is that our Viking ancestors visited and even settled in various parts of the British Isles making it hard to tell British from Scandinavian. Also there was more migration within Europe many hundreds of years back than we might realize. Finally each company uses different reference populations and techniques for their ethnicity estimates.

Predicting where your ancestors originated based on your DNA test is just not that accurate yet. The broad strokes are pretty good, but since the actual percentages vary quite a bit from company to company it is easy to see that there is much improvement needed.

Somewhat alarmed that 23andMe, which I had always thought was the most accurate of the three, did not predict Irene’s Scandinavian correctly, I decided to double check the predictions for my Norwegian-American Dad, as well as my brother who is tested at all three of the main companies.

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Ancestry Composition Numbers by Segment at 23andme.com

Did you know 23andme now provides the segment data for its ancestry composition assignments? This is a pretty recent feature and might even be useful. Unlike the other companies, 23andme does its admixture (aka ancestry composition) in chunks. This may make it more accurate than the others but in any case it means that they can give us the segment numbers. Then we can compare those to our matches.

To get these numbers, first pull down the reports menu and click on ancestry. On the initial ancestry page click on Ancestry Composition or the > symbol next to your highest group. Both are marked with my red arrow below.

ac23starts

The next page, the ancestry composition page has the pretty chromosome picture with ancestries displayed where you can change the confidence level from speculative (50%) to conservative (90%). To get a CSV file of the segments you click on Scientific Details at the top or the bottom of this page.

ac23scidet

Then scroll all the way to bottom of that next page until you see this. You can select your confidence level as well for your downloaded data.

downloadrawadmix

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Ancestry Composition Comparisons: a Case Study

Discovering where your ancestors came from is one of the more popular reasons to do a DNA test but the current ancestry composition algorithms have a long way to go. Sometimes East Asian ancestry is actually American Indian and South Asian might be gypsy or Indian Indian. Scandinavian might be British or North German and British and Irish might be Scandinavian.

Most efforts to analyze the deeper roots of your ancestry are based on samples of modern populations who self report four grandparents of a single ethnicity plus some public databases and a few ancient samples. Since each company relies greatly on their own databases of tested people, it is not surprising to see differences in their predictions.

My brother's Ancestry as shown at DNA.land

My brother’s Ancestry as shown at DNA.land

Since my brother is tested at all three companies I thought I would post the images of what each company sees in his DNA as well show the new report from DNA.land and a few from GEDmatch (both using his uploaded Ancestry.com DNA data). We are confident of our recent ancestry: 50% Southern Norwegian, 25% Bavarian German and 25% Ashkenazi.

The new DNA.land report is shown above, Hmmm, only 16% Ashkenazi.

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