AncestryDNA: Genetic Test Kit

Buyer beware! These tests do not really give you a clear picture of your ethnic makeup, they just tell you where people with similar DNA live, or have lived, recently. And they skew very European because most of the people in their database are white. I found this explanation to be very helpful: How these ancestry DNA tests work: they tested a ton of people and put all this information in a big database. Their DNA database consists mostly of DNA of white people from Europe (this will be important later). If you send these companies your DNA, they will compare it against the DNA of all the people they have in their system, and it looks at with which people in their database your DNA has the most in common. So if your DNA has a lot in common with people currently living in France, your results will come back as being a certain percentage French. And this is the really big caveat with tests like this: they don't test where people come from, they test where people are now. Because, like you said, it's really impossible to determine the ancestry of people to a country-specific level based on DNA. Say that your distant relatives came from the Alsace region in France for example, and some of their descendants still live their now. That means that your DNA might come back a certain percentage French. But that does not mean your ancestor in the Alsace was actually French. There's a really big chance that they were actually German, or at least part of a people that lived in a territory that we now recognise as Germany, nationality is a pretty recent thing. And it paints a really incomplete picture too, because every child only inherits roughly 50% of their parent's DNA: your DNA is 50% your father's DNA and 50% your mother's. Your sister's DNA is too, and it's likely not the same 50% unless you're identical twins. Meaning if you and your sister both send in tests, you'll both get different results. And if you only get 50% DNA from each parent, that means you only have 25% DNA in common with each grandparent, 12.5% with each great-grandparent, 6.25% with each great-great-grandparent, 3.125% with each great-great-great-grandparent, and so on. So you'll have less than 1% of your DNA in common with your ancestor who lived 7 generations ago, or roughly 200 years. And genes don't get passed along evenly, it's possible that you have 25% of your genes in common with one great-grandparent and 0% with your other great-grandparent. So just because you have ancestors who lived in, say, Italy, doesn't mean that your DNA results will show that you have Italian ancestry. That's also why your sister's results don't show any African ancestry: it's been countless generations since humanity moved out of Africa, the chances of the same sequence of genes surviving in the same form in both African and European populations are astronomical. Now back to the white people thing. Because the database of these companies mostly has the DNA of people from European descent, it can give your pretty specific results, because it has a lot of people to compare it to. This is great if you have almost exclusively white people in your ancestry, because you can get a result that looks really detailed which is fun. But, if you have some non-white ancestry, you're out of luck. Because these companies don't have a lot of data from for example Native American, Asian, Pacific Islander, African, etc populations they aren't nearly as specific for those groups as they are for people from European descent. If a person from Vietnam were to take the test for example, it wouldn't give them ancestry results for Vietnam, it would probably just say something like "x% East Asian". Or it might not recognise non-white descent in people at all, because the computer doesn't think that a stretch of DNA is relevant, because it doesn't see it occurring in a large amount of people because they haven't tested those people it occurs in. So that's problematic. And these tests are absolutely used to support racist beliefs.