Like this. Just how accurate are these services?
The same sort of service is available for dogs. Dog breed determination
IMHO, and the HO of many veterinarians (including a geneticist) they are garbage.
(Not saying that the human test mirrors the canine)
It’s not going to tell you anything specific - like you really are the long lost offspring of Robert the Bruce or the g’g’g’grandchild of Sally Hemmings.
The tests look for specific gene markers - mutations that occurred during human migration out of Africa and into Europe, Asia, Australia, and the New World. The tests look for DNA that is transmitted without the normal mix-and-match of sexual reproduction. That is, the Y chromosome, transmitted down the male line, and mitochondrial DNA, transmitted by the mother to all her offspring, and then transmitted again only by her daughters.
So basically, the tests can tell you something about the general population movements of your purely matrilineal line and/or your purely patrilineal line. That works out to a very small percentage of your actual ancestors, and the data is extremely rough.
Doesn’t mean it isn’t interesting, though. You can read more about it at:
Accurate enough, for what they do. But what they do is not what most people expect. As Phouka noted what they are good for, in of themselves, ia tracing a distant, putative, prehistoric ancestor. So if you are interested in the movements of ancient peoples, it has some curiosity value. Potentially a bit more so if you know something about your genealogy.
So for example, I’ve had this sort of work done and fall into a Y-DNA clade that is currently called I2A ( these designations seem to change every year ). I2A, based on modern distribution patterns and a few other things, seems to have risen in the region of modern day Bosnia in a glacial refugium, during the last glacial maximum in Europe. As it happens my father’s side of the family traces back a couple hundred years at least to modern-day Karlovac province in Croatia, just north of that. It is a reasonable supposition then that my patriline had actually remained sedentary for some 12,000 years or so in the same little patch of ground in the Dinaric Alps, absorbing languages and adapting to new cultures as they moved in and out of the area, until my great grandfather ( Serbian ) emigrated to the U.S. in 1905. Now I find that fascinating.
Thing is, that’s not guaranteed to be the case :D. That I’m I2A is basically certain. But my family’s presense in the region could be from back migration, for example. No way of knowing. So it won’t necessarily give you clear answers to family history.
What you can do is compare your data to databases of people that have done this work and tease out geographic patterns based on common mutations. If there are enough samples that match yours and if you already know a great deal about your genealogy, you might be able to dig out interesting tidbits. So enough matches on a large y-DNA profile, might point out a high likliehood of a putative common ancestor 500 years ago - if you get a strong geographic cluster of these, it can help sharpen possible genealogical origins. But again it often comes down to informed guesswork based on circumstantial evidence.
The largest commercial database of this sort I believe is at the company I used, Family Tree DNA. Sadly, not many folks from the Balkans have done extensive enough testing to be useful to me - another problem ;). You’re much more likely to have good luck if your ancestors are from the British Isles - Brits have been besotted with genealogy questions since the Victorian times and have been the most interested ( so far ) in plunking down the money for these sorts of tests.
Tests of autosomal DNA are the ones that putatively show you what percentage Innuit or French you supposedly are. And these are the ones with by far the least accuracy or at least the most uselessly confused results. Humans are quite panmictic, so parsing folks into discrete national/ethnic categories based on genetics is incredibly hard, probably not infrequently impossible. If for example, the police were after my blond-haired, blue-eyed friend, with his Anglo-Celtic, Ukrainian Jew and Bohemian/Slovene background, they would have been searching from a man from northern India based on his autosomal test :p.
There was someone that I felt particularly close to, drawn to, literally all of my life. I found out in more recent years that we have the same mitocondrial DNA. That was eery. (I had also been close to his mother and grandmother.)