Then there is the timing. WHEN were my ancestors German? What generations are giving me these results? The blog below covers this more in depth, in her critisim of ethnicity estimates:
"It’s difficult to determine which of the matching populations are more recent and which are less recent. By way of example, many Germans and others in eastern Europe are descendants of Genghis Khan’s Mongols who invaded portions of Europe in the 13century. So, do we recognize and count their DNA when found as “German,” “Polish,” “Russian,” or “Asian?” The map below shows the invasions of Genghis Khan. Based on this, Germans who descend from Genghis’s Mongols could match Koreans on those segments of DNA. Both of those people would probably find that confusing." https://dna-explained.com/2013/10/04/ethnicity-results-true-or-not/
There's a MUCH more in depth (but not over your head technical) post about Native American DNA here- http://www.rootsandrecombinantdna.com/2015/03/native-american-dna-is-just-not-that.html
"One of the most important things you must remember is that having Native American DNA is different from having Native American ancestry. This is because your potential inheritable Native American DNA could be lost every generation but you could still have real Native American ancestry in your family history. "
They are estimating, based on averages.
"Ancestry.com plasters its home page with pie charts that promise to give you a “sense of identity” with decimal-point precision.
The problem is that DNA snippets, or markers, are inconsistent. Sometimes they are passed on and sometimes they are not, and whether they are or aren’t is random. Sure, a large percentage of Native Americans may share certain genetic markers. But many Native Americans may lack the same marker, and many non–Native Americans may carry it by coincidence.
So when a DNA test comes back saying you are 28 percent Finnish, all it’s really saying is that of the DNA analyzed (most companies don’t analyze all of your DNA), 28 percent of it was most similar to that of a completely Finnish person. In the end, these comparisons are a fun but ultimately unreliable way to think about the possibilities of whom your ancestors might have been, rather than definitive proof of your ethnic background."
"We’ve assembled one the of most comprehensive DNA datasets in the world, with thousands of DNA samples from people with deep roots in each of our 26 different regions. This dataset makes up what we call a “reference panel.” Each person in the reference panel is from a specific location and has a documented family tree indicating deep ancestry in a particular region. To estimate your genetic ethnicity, we compare your DNA to the DNA of the people who make up the reference panel and then upload the results to your Ancestry account. These results can go back 500+ years and are an estimate based on current research. You can expect them to change and become even more refined as we do even more population genetic research." https://blogs.ancestry.com/ancestry/2016/10/12/determining-your-dna-ethnicity-estimate/
Hang On - Where did the Scandanavian Come From?
If you do not have scandanavian in your genealogy research, and you tested through Ancestry.com, it's most likely part of a KNOWN error in Ancestry tests. You can read more about that here -
"The problem is that their admixture percentages are simply . Period. Not a “tiny error”, not “needs tweeking,” utterly, entirely wrong. Throw it out and start over wrong. There are no secret Scandinavians hiding in the bushes, or in everyone’s family tree, and the fact that they are embracing their error and trying to turn a dime by telling people that they DO have a huge amount of mythical Scandinavian blood and they just need to use Ancestry’s tools to search longer and harder is not only infuriating, it’s unethical and self-serving."
And that makes it hard to trust ANY of ancestry's results, doesn't it?