Updated May 23, 2019: When I logged into 23andMe, it had two notices that mentioned ethnicity updates. I didn’t write them down, but they were gone the next time I logged in.
Two articles, second links to the first.
I found this in searching for DNA articles: ‘What’s my real identity?’: As DNA ancestry sites gather more data, the answer for consumers often changes: https://www.statnews.com/2019/05/22/dna-ancestry-sites-gather-data-shifting-answers-consumers/. In addition, a second search found this article which links to the first article – 23andMe Is Updating Ancestry Results Without Telling Users – Futurism: https://futurism.com/23andme-updating-ancestry-results.
From the first article:
So Kim, 34, took out his phone and consulted the 23andMe website. That’s when he discovered his ethnic identity had changed. The site that once told him he was about 40% Japanese now pegged that figure at 5%. He was, in an instant, fully Korean again.
Here’s a problem that actually isn’t addressed in the articles or by the DNA companies; in fact, few DNA experts raise the issue: As I have previously mentioned, the different DNA companies are comparing our DNA ethnicity results to people who live in other places now. If you go to YouTube and search for European history, you should find numerous videos, including one that covers 6,000 years, showing how the map of Europe has changed. Those changes may have been, but usually weren’t, peaceful migrations. Is my British/English DNA a result of ethnic natives who lived there before others moved in (Vikings, etc.)?
Unless, and until, these companies start DNA testing people who lived there when our ancestors lived there, ethnicity results will continue to be meaningless below the continental level. The exception would be isolated groups that haven’t mingled with outsiders. A good example might be the Basques as those in the France/Spain area tend to marry within their own society. Another example that comes close would be the Jews. While Jews do marry outside the Jewish faith, like a friend who converted to Judaism because his Jewish parents wouldn’t allow him to marry her if she didn’t convert. In the U. S., Amish and Mennonite groups tend to marry within the community.
I will point out that finding enough viable DNA from people who have been dead for any significant amount of time will be difficult and often impossible.