GAE and Africans

[Michael_Okoko]

@swamidass, if A&E were made and placed in some garden in the Middle East roughly 4000 years ago, then it means their descendants would have only interbred with those individuals who left Africa during the various out-of-Africa expansions. So how is it that they are genealogical ancestors of modern Africans who descended directly from ancient Africans?

[Patrick]

you are confusing genealogical ancestors with genetics. The problem with the GA&E model is not Africa but the Americas. The Americas have been populated with millions of people for at least 20,000 years. If genealogical Adam was miraculously placed in the Middle East only 4000 years ago, how could Gen. Adam be in the ancestry of all Native Americans by the supposed time of Jesus, 2000 years ago? For all Americans to have Gen Adam as one of its ancestors would only have occured until about a century after the arrival of the Spanish with their bible containing the Genesis fairy tale.

Origin

[Michael_Okoko]

@Patrick

you are confusing genealogical ancestors with genetics

I did not and there is nothing in the OP that implied so. Perhaps you are the one who has got it muddled. Can you spell out my confusion?

@Patrick

The problem with the GA&E model is not Africa but the Americas

So can you tell me how modern African most of whom are direct descendants of ancient Africans came be to genealogical descendants of A&E?

[Faizal_Ali]

My understanding is that GAE can have existed at any time in the past that would allow it to be consistent with the extant genomic data. But, luckily, the guy who came up with GAE is a member of this group, so he can confirm for himself.

[thoughtful (Valerie (non-scientist))]

@Michael_Okoko

So can you tell me how modern African most of whom are direct descendants of ancient Africans came be to genealogical descendants of A&E?

I’m going to attempt since in case your confusion lies where mine has been in the past.

To be a genealogical descendant all you need is some random descendent(s) of Adam and Eve to wander to Africa and intermarry in the ancient past. They might not contribute anything to the genetics of modern Africans

But because of the recent discussion of male-line ancestry and your knowledge of the Bible, you may be thinking of the male-line genealogical ancestor of everyone, which is also Y-chromosome Adam. If Adam and Eve were created inside of a population, then God would have had to providentially preserve Adam’s male line, and you’d have to defend y-chromosome Adam at 6000 years, similar to Jeanson is at 4500 years.

If male-line genealogical ancestry is also theologically important to anyone, they may as well take the YEC view because it doesn’t require special intervention not described in the Bible. I don’t think that’s necessarily obvious to everyone who reads the book or hears about the concept.

[Michael_Okoko]

@thoughtful

To be a genealogical descendant all you need is some random descendent(s) of Adam and Eve to wander to Africa and intermarry in the ancient past. They might not contribute anything to the genetics of modern Africans

I know what it means to be a genealogical ancestor, and not a genetic one.

More importantly, Africa was composed of many separate tribes 10,000 years ago, so I don’t see how intermarriage between descendants of A&E and members of a handful of those tribes would get A&E to the status of genealogical ancestors of all modern Africans.

I also used this scenario of extensive interbreeding between African tribes 10,000 years ago to rationalize how A&E could be ancestors to all modern Africans. However, a recent paper by Lipson et al., 2022, seems to challenge that thought as it suggests the African continent-wide interbreeding ended more than 18,000 years ago, many thousands of years before the timeline the young GAE posits the descendants of A&E lived and interbred with POGs

From the paper’s “Discussion” section:

“In contrast to previous studies, our results show that a two-way clinal model extending latitudinally from eastern to southern Africa is insufficient to explain observed patterns of genetic varia-tion in ancient sub-Saharan African foragers. Here we demonstrate that central-African-related ancestry (closest to present-day Mbuti among sampled populations), along with Mota-related and southern African-related ancestry, was ubiquitous (in varying proportions) from southwestern Kenya to southeastern Zambia (Fig. 3), with all three components present by at least about 7 ka in Tanzania and about 16 ka in Malawi. Furthermore, when considering ancient African foragers from a wide range of time periods, ecological contexts and archaeological associations, geographical proximity remains the strongest predictor of genetic similarity 5,11. Such a pattern may indicate that long-range migrations were rare in the terminal Pleistocene and Holocene, when these individuals lived. This hypothesis is supported by the signals in our admixture graphs of excess genetic relatedness at subregional scales but not at longer-distance scales. Although it is not possible at present to estimate when and how quickly this three-way cline emerged, it must have post-dated both the emergence of the Mota-related lineage around 80–60 ka 12,16 and, with respect to the central-African-related ancestry, the split between Aka and Mbuti less than around 50 ka 25,26.”

https://www.nature.com/articles/s41586-022-04430-9

I could be misinterpreting the paper and that’s why I am asking @swamidass for clarification here.

The rest of your post is irrelevant to my question.

[Herman_Mays]

@Faizal_Ali

My understanding is that GAE can have existed at any time in the past that would allow it to be consistent with the extant genomic data.

Convenient.

[Herman_Mays]

Raff’s book is excellent by the way. One thing she points out is the very long history of outside people trying to place native peoples in THEIR religious context. I think unfortunately people still are trying to do that.

[Mercer (John Mercer)]

@Michael_Okoko

I could be misinterpreting the paper and that’s why I am asking @swamidass for clarification here.

Your request is a reasonable one. I wonder why @swamidass hasn’t responded…

[Michael_Okoko]

Still no response from @swamidass

[Mercer (John Mercer)]

Still no reply to your perfectly reasonable question…

[swamidass (S. Joshua Swamidass)]

Sorry for the delayed response, but my work is busy now. It is a perfectly reasonable question, but its also something outside the purview of my day job.

For now, I will ditto this response from @john_harshman.

@John_Harshman

@Michael_Okoko

My current quarrel with the GAE is how A&E became genealogical ancestors to all modern Africans 6,000 years ago in the face of significantly reduced long-range migrations.

The solution is a chain of short-range migrations. Think of it as diffusion. And it isn’t 6000 years ago; it only has to be 2000 years ago. Note that genealogy can make the trip much more easily than alleles can.

And direct you to the references and reasoning in my book, primarily the chapter on isolation. As far as I know, the argument there does not need to be updated in light of any recent scientific findings, at least not yet.

Note also the studies cited suggest that migration was rare, not that it was non-existent. All a recent GAE requires is rare migration, and may not even require any long range migration in Africa to work.

[Michael_Okoko]

@swamidass

For now, I will ditto this response from

Which I find unconvincing due to the reason I provided in that thread.

@swamidass

Note also the studies cited suggest that migration was rare, not that it was non-existent.

True, but there is nothing that suggests it was the genealogical descendants of A&E that made those rare trips.

@swamidass

All a recent GAE requires is rare migration

Yes, but unless you want to claim that God miraculously kept moving the genealogical descendants of A&E to every single African tribe in all parts of the African continent and had their descendants dominate after a time, then I don’t see how rare migrations save the GAE in Africa.

[swamidass (S. Joshua Swamidass)]

Hopefully it will make sense with some thought. Perhaps reread the chapters I wrote on this specific topic

[John_Harshman]

@Michael_Okoko

Yes, but unless you want to claim that God miraculously kept moving the genealogical descendants of A&E to every single African tribe in all parts of the African continent and had their descendants dominate after a time, then I don’t see how rare migrations save the GAE in Africa.

You aren’t understanding the process. Some descendant of A&E marries into a village. After a while, through continued marriage of that person’s descendants, everyone in the village becomes a descendant of A&E (and of course of many other people at the same time). Then someone from that village marries into the next village. And so on. Genealogical descent spreads, not just for A&E’s descendants but for everyone’s. Whether this is enough to spread descent from A&E throughout Africa in 4000 years depends on local, short-range migration rates, and those rates don’t have to be very large, and don’t have to involve much gene flow, for that to work.

[Mercer (John Mercer)]

@John_Harshman

Whether this is enough to spread descent from A&E throughout Africa in 4000 years depends on local, short-range migration rates, and those rates don’t have to be very large, and don’t have to involve much gene flow, for that to work.

But given that Africans have high polymorphism, it should be much easier to test that hypothesis for them than for any other group. Has that been done?

[Faizal_Ali]

@Mercer

But given that Africans have high polymorphism, it should be much easier to test that hypothesis for them than for any other group. Has that been done?

GAE has been specifically designed to be untestable as a scientific hypothesis. So if you test it and it is confirmed, @swamidass has failed.

[John_Harshman]

@Faizal_Ali

GAE has been specifically designed to be untestable as a scientific hypothesis.

Not quite. Various parts of it are testable. The demographics are. The poofing isn’t. Here @Mercer apparently is proposing to test the local migration rate parameters necessary for the hypothesis to be plausible.

[Herman_Mays]

@Faizal_Ali

GAE has been specifically designed to be untestable as a scientific hypothesis. So if you test it and it is confirmed, @swamidass has failed

Convenient

[Michael_Okoko]

@John_Harshman

@Michael_Okoko

Yes, but unless you want to claim that God miraculously kept moving the genealogical descendants of A&E to every single African tribe in all parts of the African continent and had their descendants dominate after a time, then I don’t see how rare migrations save the GAE in Africa.

You aren’t understanding the process. Some descendant of A&E marries into a village. After a while, through continued marriage of that person’s descendants, everyone in the village becomes a descendant of A&E (and of course of many other people at the same time). Then someone from that village marries into the next village. And so on.

Um, no misunderstanding here. You misunderstood my comment because what you described here is exactly what my comment is saying.

@John_Harshman

Whether this is enough to spread descent from A&E throughout Africa in 4000 years depends on local, short-range migration rates, and those rates don’t have to be very large, and don’t have to involve much gene flow, for that to work.

This assumes every intermarriage between the descendants of A&E and people of the tribes they encountered was successful and adequate to ensure their own descendants dominated after several generations, which I find hard to believe in th absence of good evidence. This also assumes the descendants of A&E kept on migrating to other parts of Africa: what if some didn’t make it? Or some decided to settle and not move anymore? I am seeing the need to invoke miracles here.