Friday, 4 May 2018

Info: Your 23andMe Ancestry Composition has been recalculated

This is a public service announcement from me, Miriam.

Have you noticed any small changes to your Ancestry Composition results lately? Perhaps you've even lost whole categories?

After the last update, I lost my <0.1% East African segment on chromosome 6. It was reclassified as "No Data Available", and my admixture total is now 99.9% instead of 100%.

I contacted 23andMe and asked what had happened, and got this reply (the whole reply is not shown, only the parts that are relevant to the general public):

Hello Miriam,

Thank you for contacting the 23andMe Team. We recently released an update to your report that impacts the smallest percentages in your Ancestry Composition results. Any assignment previously labeled as <0.1% was either rounded up to 0.1% or rounded down to 0.0%. Assignments rounded to 0.0% were removed from your results, because assignments of this size may be noise within the thousands of windows analyzed by the Ancestry Composition report.

In this case, it sounds like your East African ancestry assignment was updated to 0.0% and removed from your report.

Note that this update is independent from the recent update comparing your results to an additional 120+ regions.

In other words, if you've seen your percentages go up and down - for instance, 40% instead of 39.9% - or if you've lost your <0.1% East African just like me, then it's simply because the number was rounded up or down. My East Asian score was actually rounded up, from <0.1% to 0.1%, and my Native American segment (<0.1% total) seems to have been incorporated into the East Asian segment right next to it. The 23andMe rep did not mention category reassignments, but in this case I believe East Asian is probably correct and Native American is probably wrong, so I'm not complaining.

In the case of my East African segment, however, I believe the rounding down was a mistake, and that the segment is in fact real. The reason for this is that I have verified it as real through comparison with my mother in several GEDmatch chromosome paintings. The fact that something is small does not mean that it is noise, and if my mother had tested at 23andMe and our results had been phased against each other, I have a very strong suspicion that the East African segment would reappear.

I'm waiting for further explanations from 23andMe as to why the segment was reclassified as "No Data Available" rather than the more appropriate "Unassigned", and whether they agree that the original East African assignment might in fact be real after all. I will update this blog post when I get their response.

Update: I did get another response, but they did not understand my question. They thought I was asking what "No Data Available" means, which I do know. I don't think I will take this any further.

I'm going with my East African segment being real, as there was no re-analysis of my data, but simply a rounding down of existing percentages.

1 comment:

  1. Still have NA, SE Asian and South Asian DNA.

    Love that you fight for the rightful inclusion of your African DNA. So annoying that when genealogists see a person’s DNA skewed a certain way that they look to downplay the low levels of DNA when skewed in a different direction. shows I have low level of European DNA, Ashkenazi, and am related to many people who have European Jewish DNA. Belong to a Jewish DNA group and was questioned whether its noise. Some of my cousins, white and black, who have Jewish DNA are in the group too. Had to point that out to the admin. 23andMe still has some of my DNA unassigned and they’ll eventually discover that some of it is Jewish. Have to self- report.