Have you all heard of "23andme" where you can get your DNA tested from a saliva sample for all kinds of things? A relative of mine had it done to see his ancestry among other things. No real surprises: predominantly European but with an unexpected tiny smidgen of South Asian. (Who knows how far back that goes?) The European was broken down into many subgroups, mostly all Western European nationalities, but also including Ashkenazi Jewish. (I wonder why no Sephardic Jewish because that should be in there somewhere.)
I'm surprised at the detail. I had no idea you could get that much specific information about ancestry from DNA. Is it possible to explain how this is possible?
One way to think about how it works is book copying as an analogy. In fact, copies of books are related this way too.
Let's say you have a hand copied book somewhere in Eastern Europe. As in the real world scribes can be very good copiests but also not precisely perfect.
If our book is copied a lot then some of the copies are bound to have errors in them. If those copies are then copied at some other place the errors will be copied too and, often, new ones added. If this continues you can see that it will be possible to construct a relationship between the book copies.
You might not be sure of which is the original but if you pick a copy as a starting point you can judge which is the next made from it. You infer this because the next copy will have the fewest errors from your assumed orginal
You will see that one error will appear in a whole series of copies but not in another bunch of copies. From that you can infer which copies are from one book and which from another.
It isn't, of course, a perfect analogy since the copies only each have one "parent". I guess you could say that sometimes a book is copied half from one copy and half from another.
From this you'll get a whole bunch of subgroups and branches just like with the DNA.
That's a good description of how the ancestry of ancient books is reconstructed, but I don't see how "errors" get into the DNA question. I'm just amazed that there would be anything IN the DNA that could actually indicate, say, a 2% South Asian ancestry. Which genes or other part of the genome could possibly tell us that? Doesn't that amaze you too?
Careful Faith, if you go too far down this path you'll start to understand something you won't like
I'd love it. I had my DNA analysed. It turned up that I am of predominently Northern European origin through my Mitochondrial DNA.
My surname is a derivative of German Jewish people. It also shows through DNA. And my Scottish grandmother also shows in the DNA. Also some derivative of Malaysian DNA and some Bushman DNA. And then also some Denisovian DNA to the boot. They didn't find much Neanderthal DNA, though.
I'm a close relative of people living in Hamburg and Beijing and London and New York and Buenos Aires and Sydney and Soweto! That's cool!
... but I don't see how "errors" get into the DNA question
Remember? You have errors, I have errors we all have errors. The DNA copying mechanism is just like our hypothetical (and real) copiests. Very, very good but imperfect. It is difficult when you have to be told the same thing multiple times.
What the things like "2% south Asian ancestry" are saying (though now we might start to step out to where I am not an expert) is that we see copies (you and I) that have errors that are much more common (so appear to have originated) in that location.
That is where the book copying analogy has to be made more complex because all most all the time books don't have two parents and so can't bring in small amounts of other lines of decent.
I find it very awesome to think (I got the national geographic sequencing done) that there was an individual in central Asia about 40,000 years ago that is a direct Y-chromosome ancestor of me. Of course, they had to be somewhere and there are gillions of them but the DNA thing somehow makes it more right there and real.
The fact that we can read our ancestral history like this is amazing to me. It keeps getting better and more detailed to.
I don't think that Faith has the ability to understand much. It is an interesting subject for normal people, though.
The first comment is simply a personal-attack, and is totally uncaused it seems, it seems to come out of thin air, an atheist being mean-spirited just for the sake of being mean-spirited. Perhaps insulting people is your attempt to show you have superior morality? Oops, I guess that's to shoot yourself in the foot then.
The term, "normal people", is used as a question-begging-epithet, because it implies that Faith is not normal.
This means you have to define normal for us. Are you implying that it is abnormal to not accept that a primordial, fictional lifeform emerged from a swamp and gave rise to fleas, peas, cheese, bees and hairy knees? Let me get this right, I have to believe in a fictional swamp, a fictional earth and a fictional lifeform. I also have to believe in fictional pre-seahorses, pre-bats, pre-pterosaurs, pre-starfish, pre-jellyfish, pre-apes, pre-platy-pi, pre-Ichtyhosaurs, pre-dugongs, pre-manatees, pre-dragon flies, pre-winged beetles, pre-ants, pre-spider, pre . basically pre-everything. Everything that depends on 0% fossil evidence, which means I would still be typing, "pre-X species" come Christmas 2020.
I call them, "fictional" because as far as I can tell, I have to imagine these things existed.
Sign me up for the, "abnormal" group right now then. Lol.
Yes I'm slow but it was dawning on me that the idea is that some mutations mark particular groups of people and that's how they can give us a genetic portrait of which groups we're related to. Although Tangle seems to believe I'd be offended at the idea of mutations, that's a bad misreading of the contexts in which I've objected. I object to the idea that they are normal events that make normal alleles, I object to the idea that they contribute anything genuine to genetic diversity and so on. But there's no reason I should object to their identification of people groups; in fact that's an unexpected benefit from an error.
So are you all saying that it's mutations and mutations only that give us the ability to trace our ancestry?
I object to the idea that they are normal events that make normal alleles, I object to the idea that they contribute anything genuine to genetic diversity and so on. But there's no reason I should object to their identification of people groups; in fact that's an unexpected benefit.
Careful, you're getting closer....
Je suis Charlie. Je suis Ahmed. Je suis Juif. Je suis Parisien.
Life, don't talk to me about life - Marvin the Paranoid Android
"Science adjusts it's views based on what's observed. Faith is the denial of observation so that Belief can be preserved." - Tim Minchin, in his beat poem, Storm.