My father's side of the family are all from the Azores Islands in the middle of the Pacific and are all Portuguese. I haven't had mine done yet but my brother's came back with only a smattering of Portuguese, around 20%, even though our grandparents and great grandparents all came from there.
Important to remember that DNA doesn’t have a nationality. These tests look at, among other things, SNPs. These are features of DNA that are shared amongst people(s) who spent enough time having kids together as to have SNPs that occur more randomly than chance. If there is a paucity of data from a particular group of people, then the test will not be as accurate. If there are large bits of data, the tests get better. As people groups move around, nationalities can shift relative to the SNPs, meaning that either your ancestors’ group of people possibly were not adequately sampled, or are from an ethnographic group which was inslular in Portugal, or possibly other things.
At least from as recently as 6 years ago, 23 and me looked at an astounding number of SNPs. Something like 690,000 of them. This is still a small sample of an individual’s total genome. By small, I mean around .01%.
I’m as American as you can get, but looking at my DNA, you wouldn’t be able to tell me apart from a person with a mixed background from Europe. Without context, you probably couldn’t tell when and how my particular genetic mix happened. The time data is critical to understanding what my ancestors’ nationalities may have been.
Also had the slave ships crash on the south side of the Islands and he has some small percentage of African DNA show up too although it showed up as North African, which I believe would be unusual for slave ships.
Dan, the historical ethnographic data of the Iberian Peninsula suggest that one should expect this genomic result!
This analysis:
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Is pretty neat to look at.
The same could be said for other parts of Europe, even Britain, which were contacted by the Roman Empire, but to a lesser extent.
Keep in mind that even two generations removed you are looking at four dna contributors, three generations eight contributors, etc., etc. By the time you get to the mid 1800's you are looking at 16 or 32 depending on your age.
Very true and very insightful. Also, recombination happens with each generation. However, if those generations we are referring to come from the same group of people, then the data would simply point more strongly in that direction.
A final word: most of these SNPs are in “junk DNA” (a term I dislike, but is OK for this discussion) and have little bearing on health or anything else. We are one big family, and all children of the Creator. Eugenics, racism, and other evils perpetrated on people just because they seem different were just that: Evils. I hope that our new technologies and advancements in this area don’t ever contribute to more division.