I'm confused too. You only need to go back 30 generations until you have 1.07 billion ancestors: https://en.wikipedia.org/wiki/Most_recent_common_ancestor. That means any old bones we dig up that are over about 4,000 years old will almost certainly be one of our relatives. Can anyone the article's significance in this context?
If only half the population in Europe shared a most common ancestor 4000 years back, that would be absolutely shocking. But this article is misleading, and that's not what the research says.
It's actually not about ancestry in general, but purely about patrilinear ancestry [0], which doesn't have the same kind of fan-out. If you go 30 generations back, you might have a billion ancestors, but only 30 patrilinear ones.
[0] That's the measurement they have to make. We have technology to measure patrilinear ancestry through the Y chromosome, and matrilinear ancestry through the mitochondrial DNA. But there is no way of doing the same for ancestry in general.
I don't think you can apply the same techniques, since they depend on a special property of the Y-chromosome and mitochondrial DNA: they are not affected by sexual reproduction, only by mutations.
Huh, you're right- studies on the altogether most recent human common ancestor are all based on pure statistics. I'd thought that genetic recombination could be accounted for, since its not as though genetic information (and the mutations therein) are being lost in the process, but apparently no one's found a way to do this yet. Interesting... ! :)
If you go back 30 generations, many, if not most, of your ancestors will be ancestors on more than one path. Except when you are a Spanish Habsburg, then going back just three generations might be enough.