I don't see how it follows that there were many more humans. Math says that all people eventually become descendants of every single individual (kinda "diffusion"), or die off completely.
Say, there were not "many more", but just like 15% more. Like 1150 alive, and descendants of 1000 of them did not die off completely. Sounds plausible.
Ignoring that it might be related to stations where idk. most people can't have children (or they at lest won't survive).
The other options is that there can be while groups of humans in a distant place alive at the same time, but they didn't survive long term and didn't re-mix with the "bottleneck group" at lest not in a way detectable genetically (idk. how precises the methods in question are).
The point here isn't that a genetic bottle neck implies the presence of other humans, but that it doesn't say that there can't have been other humans, just that other humans genes didn't carry forward until today.
Agree, that's a possibility. But I don't see how it follows necessarily. I provided an example of how it might have been otherwise. I would just change "There were _many more humans_ alive" to "It's also totally possible that there were many more humans alive".
There might have been many times more people living entirely isolated populations which would have left no descendants. Which is not unlikely given the extremely low population density.
Even if all modern humans were confined to Africa if there were only 10s of thousands of them distributed across a significant part of the continent there is no way they would've had actual direct ties to each other.
Yes, but people had way more children. E.g my grand-grandparents had many kids, and counting only surviving ones is still 3x more than my grandparents. Combined with much earlier parenthood, humans were "diffusing" their genes way faster than we do before dying earlier.
Say, there were not "many more", but just like 15% more. Like 1150 alive, and descendants of 1000 of them did not die off completely. Sounds plausible.