No, that’s not the problem. Even if you assume that the root of the human tree is much shallower than we think, i.e. even if you assume YEC, his method does not work. This shows Jeanson to be comically inept, even in his own terms. You desperately need to find a new hero.
Rather they will be very quiet about it. If you don’t have anything nice to say, don’t say anything. If Jeanson were on to something, however, that would not be the case. They would be trumpeting it. The silence in this case is damning.
Silly population geneticists wasting their time developing tools like PSMC and ABC - if only Jeanson could have told them all years ago that all they have to do is count the number of branches in a phylogeny to estimate population sizes through time!
Why “almost”? Once your method is shown to be useless, you should stop. Period.
Not that many times. He’s fudging, and he’s misrepresenting the sources he claims to be using.
You are understanding Jeanson’s claim. Jeanson’s claim is wrong.
Coalescence theory isn’t about evolution, per se. It’s about how ancestry works. To state the problem very simply, Jeanson’s model doesn’t consider any men who have only daughters. Their Y-chromosome lineage drops out. In any population, some Y-chromosome lineages will disappear in every generation because of such men. Even in a population of constant size, that means that the Y-chromosome ancestry will narrow down as you go back in time, down to a single individual. But that single individual would have been only one man in a population of many millions of men, most of whom would have current descendants. But he’s the only man whose Y-chromosome descents don’t end at some point in daughters.
It’s about mtDNA, but works just as well for Y chromosome DNA if you swap the sexes.
Each row is a different generation, so the top row represents the first generation of this population, and the bottom row represents the 5th generation. As you can, this hypothetical population has a constant population size - there are 8 women (men) in each generation. The lines connect ancestors with descendants.
In the latest generation (bottom row), you can see that there are only women (men) coloured in black, indicating (along with the connecting lines) that they descended from the woman (man) coloured in black in the first generation (top row).
If we construct a phylogeny using the 8 modern-day (latest generation) women (men) and then apply Jeanson’s method to it (counting the number of branches through time), we would conclude that the population grew from 1 in the first generation, 2 in the second, 3 in the third, 5 in the fourth, and 8 in the fifth. But we know that the population size was constant, so Jeanson’s method leads to a completely incorrect conclusion and is therefore invalid.