is there some sort of cutoff point where scientists decided “everyone in Ireland 100,000 years ago will be considered 100% Irish”?
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Mutation. Which is how you can see lineages in DNA.
Black skin, white Kanin, Asian eyes, people mutate.
Evolution man….
This is a semantic issue, if you define nationality/ethnicity in terms of ancestry from 100,000 years ago then sure. In practice people don’t trace their ancestry back so far, and it’s usually more on the order of a few hundred years at most. On those time scales describing everyone as African would be misleading and unhelpful.
I’d also like to point out that the difference in genetic material between a totally isolated population like the Sentinelese, and you… is almost 0. We’re a single species, we all can interbreed, we’re all painfully similar. The fact that where we’re born and some very surface-level morphological differences carry enormous social weight, doesn’t make them genetically significant.
Edit: A lot of people are talking about mutations, and I just want to emphasize that the sum total of genetic differences between a genetically isolated group like aboriginal Australians (isolated for up to 50k years) and the queen of England is virtually nil. We’re talking percentages of percentages. To illustrate this keep in mind that all breeds of dogs, from toy poodles to cane corso, are more closely related to each other than any of them are to wolves. The differences between domesticated dogs account for less than .2% of their DNA.
Those DNA ancestry tests aren’t exactly “scientific”. Basically the way they work is that they have a database of people for whom they have both DNA test results and some kind of statement about where they think their ancestors are from. They compare your results to the people on the database and give you numerical scores based on how similar your DNA is to those whose ancestors are supposedly from a given region. Different tests can give you quite different results, because they use different databases and different methodologies.
It wouldn’t be possible to have a hard cutoff point at, say 100 thousand years ago, or even 1 thousand years, because (a) there have been mutations since then and (b) it’s hard to trace population genetics that far back with much certainty, as almost all of the available DNA data is recent.
There are serious scientific studies of population genetics too, but they tend to focus on the distribution of specific genes instead of more nebulous concepts like “African DNA”.
Depending on definitions we do. It is just unhelpful information so it is rarely talked about this way, except when talking about the origins of humanity. The evidence is that all the non-African diversity in humans nests within the clade of African diversity. Basically everyone outside of Africa can trace their ancestry to a group that is only a small subset of African diversity.
It’s a matter of definitions, at the end of the day. Humans share the vast majority of our DNA with each other anyways – hell, we share most of our DNA with bananas. But the traits that help us to tell someone’s ancestry down to specific countries are the traits that either developed after humans began to migrate to various places around the world, or else they’re traits that became super common in specific populations.
There have been mutations in human DNA since the Out Of Africa migration. Of course, there were also mutations in Africa during that time. So in a sense, no one has (ancient) African DNA. Instead, we’re all at different points on a tree that begins with ancient African DNA and descends down to the present.
However, non-African populations all share some early mutations. In other words, they form one cluster on that tree, while native African populations form another. It’s in that sense that Africans tend to have one set of genetics while everyone else tends to have another.
On the other hand, if you go further up the tree, humans share our DNA with other species from which early humans diverged long before the Out Of Africa migration.
It has with how the genetic testing companies decide what genetic sequences are “assigned” to a particular country or region.
Basically they take samples from a bunch of people in a given geographical area and note the common sequences in that area. When you get your DNA analyzed the compare your sequences to those of the people known to live in that region. if they see your gene sequences are most similar to the ones they collected from Germany, they’ll say you are likely German with a percentage similar to how much of your sequences resemble those of people from Germany.
There are/were some issues with France. France makes it illegal to test DNA for ancestry. Even though it is illegal some still get it done (or do it in another country). So while many companies can pinpoint locations in a country from which your ancestors hail, the location of your ancestors in France is harder to determine.
All DNA is Human DNA, but there are “variants” in the genetic code that happen at random. Some are very minor and don’t produce any visible changes. Some produce some visible changes in the human. When we sequence the DNA from people in different regions, we see that some populations all have some similar variants. We can say these variants are common to that region.
DNA variants happen within humans all the time and if they aren’t immediately deadly variants, they can be passed to children and they’ll pass it to their children, etc. Since people typically breed with people in their region, these variants can become common in that region but are unlikely to be found outside that region.
By the way, these variants are SUPER tiny parts of the entire DNA. It’s like changing the font on one word in one book in an entire library.
So there isn’t any “African” or “European” DNA. It’s all human DNA, its just that if you look closely, you can find the book with the italicized word for Ostrich and then you can reasonably conclude that the library of books came from the same region as the other libraries that have the italicized word for Ostrich in it.
When people say their DNA is traced to a geography (“I have Irish DNA”) it means something extremely specific. There are genetic markers called haplogroups that are inherited directly from one parent.
From time to time mutations in a haplogroup will arise. This mutation will be inherited by all decedents, meaning that a distinct haplogroup corresponds to a distinct maternal or paternal lineage where one parent was the first human to have the mutation. Every human who carries the mutation is a direct descendant on either the maternal or paternal line of the first person to carry the mutation.
If a DNA test says you are genetically Irish, what they mean by that is that you carry a specific mutation, likely [this specific mutation](https://en.wikipedia.org/wiki/Haplogroup_R-L21). Everyone with that mutation can be traced in a direct line to a single parent possibly around 4,500 years ago and this specific mutation is most prevalent among Celtic peoples and not particularly prevalent outside of Celtic/Irish populations.
Don’t read too much into this though. Not everyone in Ireland will have this mutation and there will be people of many different ethnicities who have this mutation. You could carry this mutation and be a Chinese person and not have any record of Irish ancestry. This mutation just means that your direct paternal lineage traces back to a single ancestor in Europe sometime in the Bronze Age. It doesn’t say anything at all about the thousands and thousands of other ancestors you have.
Change how you’re framing the thought. It’s 100% human DNA. But DNA undergoes mutation so there are small variants among every single human who isn’t a twin.
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