“Population” is poorly defined. How many are there now? How many have there ever been?
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Not all. But most, and any that survive for a generation or two are more likely to survive to the present, and any lineage that survives to the present will be universal.
I don’t know what the latter means.
I don’t know what that means either.
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So how do you know the descendants of A&E weren’t part of the “but most”?
It means a lineage dies out due to being completely isolated in the long run.
Same explanation as before.
That’s my point.
Wouldn’t an accurate estimate of all 3 numbers be necessary to calculate the likelihood that all humans in Africa 2000 years ago were ancestors of a couple that lived 6000 years ago?
That appears to be pure guesswork to me.
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You have that backwards. You need them not to be part of the “most”.
This is not something that happens, as far as can be told. No population is completely isolated. That’s sympatric speciation you’re describing.
It is? Then I don’t know what you’ve been saying. What I mean is that populations are not self-contained. They have fuzzy edges.
No. It’s only necessary to know that none of them were genealogically isolated. Admittedly, that’s an assumption. But it’s based on observation of the present world and of modern genetics. There is some historical gene flow everywhere. “Genealogy flow” is necessarily greater.
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As a rule, yes, but for this to work it has to have been universal over a massive continent over 4000 years, a very short timeframe.
The connectivity of the present world is not a good model for the world of 6000 years ago.
But most of it was out of, not into, Africa. IIRC European colonization occurred well after 0 AD.
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I don’t see any reason to postulate any completely isolated population over that time frame. And the population would have to be completely isolated on all sides. Any leakage from any direction links them to the world.
But modern genetics reflects past gene flow, if the sample is properly chosen.
It’s not European colonization that counts, just the migration between adjacent communities. The Mediterranean and the Sahara are partial barriers, but only partial. There has always been contact across both, not to mention contact along the Nile and across the Red Sea. You need complete isolation in order to avoid GAE. There is only one population that was arguably completely isolated during the relevant period, and that’s Tasmania.
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But you said the “most” have descendants today, while the “few” went extinct, so how do I have that backwards?
Some “Osu” lineages must have died out in the past because of isolation. I don’t have evidence to support that assertion but its very likely.
I don’t see any reason to postulate that there were zero populations isolated from the descendants of A&E over that time frame. There’s a difference.
So do those data exist?
That was a joke about the only European colonization I know about. The migration between adjacent communities has to flow from A&E. If they were in Africa, I would be ~10% as skeptical. The problem I see is trying to place them in the Middle East.
You only need complete isolation from descendants of A&E.
Agreed. That’s another population that has suffered great abuse at the hands of white Christians. However, @swamidass’s target audience is unlikely to know anything about Tasmania.
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One of us has lost the thread of this discussion. GAE requires that A&E were part of the majority of people living at the time whose lineages didn’t become extinct.
Why? Are Osu populations isolated from other Osu populations? Is the total Osu population unusually small?
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Is it plausible that there were such isolated populations? What’s your argument, if so?
They probably do. Not something I keep up with.
Why? There’s plenty of migration from the Middle East, into Egypt, from Arabia across the Red Sea, and into North Africa and across the Sahara. Across the Indian Ocean from Asia to East Africa is also an ancient route. How is this a problem?
Given that descendants of A&E diffuse all over in the absence of a barrier, that’s eventually the same as complete isolation.
Tasmania has been extensively discussed here.
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Oh! I now see why we have disagreed till now. I didn’t know this was a required assumption.
They were kept physically and socially isolated in their resident communities.
No. In fact, they could marry from other tribes as long as those tribes didn’t know their Osu status.
Yes, relative to the population of freeborns in their respective communities.
I don’t see how that causes them to die out. Are you saying that each Osu community is isolated from each other, and they aren’t allowed to travel?
So there you have it: not isolated.
Small enough for entire communities to die out?
Like I said in the other thread, a small population and limited interbreeding opportunities due to the presence of heavy observance of the caste system. I expect some lineages to die from these factors.
Not all.
In some cases.
Do you know of any such cases?
You’re neglecting the temporal component.
While it’s obvious that spread is inevitable, there would be only 200-300 generations for covering a huge continent. There’s every reason to assume that the connection from one population to another would take several generations to propagate within the recipient before a genealogical descendant would get to the next population.
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None that I know of.
Mod Edit: fixed quoting.
If you think the migration parameters used in the simulations are too optimistic, you should try something you think is more plausible and see where it goes. I haven’t looked at it myself.
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