New Type of Ancient Human Found—Descendants Live Today?

What's there to interpret? If we're talking about strictly modern H. Sapiens, and the 3 mDNA lineages that survived to populate everything outside of Africa - we're talking about "out of Africa" pretty much by definition.

I'm confused as to the point you're trying to make.Jon

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Check out No webpage found at provided URL: Apollo's Temple!
Ignorance is temporary; you should be able to overcome it. - nwr

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Indeed; and I would say unlikely even in past times during which pre-sapiens made the transition to sapiens. We have yet to find any modern population of people that has been isolated long enough to speciate, and the on-off isolation offered by oscillating geographical and environmental factors does not seem to provide sufficient time for speciation. It seems reasonable that the factors that have allowed people the world over to maintain their identity as members of the same human speciesincluding and especially those natural ones from pre-technological and pre-exploration timeshave been in effect since the erectus expansion.

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Since the pre-sapiens populations were far more diverged genetically than any modern populations, your confidence in the similarity in the processes involved is misplaced.

Jon, since you haven't answered my question, I'm going to repeat it: "If there had been a single population with some regional diversification and a constant flow of genes between neighbors, how did 95+% of Scandinavian alleles come to be of African origin, while virtually no African alleles are of Scandinavian origin? What kind of gene flow could possibly produce that situation, short of substantial numbers of people moving (on average, and over many generations) from Africa toward Scandinavia? "You seem to think there's a model based on gene flow, without migration, that could explain this most obvious feature of human genetics. What is it?

I've answered this question a couple of times already. Here are some quotes from me regarding the matter:

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Jon in Message 65:

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Not when the 'Paleo-African' groups were the largest, most dense, and central groups of the world population. Then the dominance is entirely consistent and expected given either the MH or OOA model. Genetic traits of the central, large, denser groups of a population will naturally dominate the population as a whole whether through hybridization or OOA-type migration. Dominance of African alleles does not necessarily support the OOA model anymore than it supports an alternative model.

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Jon in Message 39:

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Of course it can. Africa being the origin of pre-sapiens (who, of course, did migrate) and the location of the greatest population density, we would naturally expect Africans to make the highest contribution to the world-wide population gene pool. It would be ridiculous to expect less dense, peripheral populations to contribute an equal amount of genetic material to the world population (which includes themselves) as the denser, central populations.

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I await your critique.Jon

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Check out No webpage found at provided URL: Apollo's Temple!
Ignorance is temporary; you should be able to overcome it. - nwr

Hi, Jon. Oh, so, when you said "pre-sapiens," you were referring to Neanderthals and Denisovans? I didn't realize that before. That's not strictly accurate, since H. sapiens didn't evolve from either one.And, let me repeat myself: evidence that H. sapiens and Denisovans interbred is evidence that they existed in geographical proximity. And, evidence that Denisovans are extinct in Siberia, where H. sapiens can now be found, is evidence that the latter replaced the former, isn't it?----- I'm still amazed that you think migration is an extraordinary claim.----- What is so special about this one period is that, before this one period, we see divergence in regional populations, and [i]after this one period, we see divergence in regional populations. But, during this one period, we see convergence between regional populations.This implies that something was happening at this time period that was different from what was happening in the prior and later periods. Yet, your model proposes that one mechanism (genetic flow) explains all three periods of time.----- Theoretically, sure. But, let me repeat my earlier comment: total saturation of a population with "irrelevant" traits by genetic flow alone has never been observed in the real world.On the other hand, total saturation of a population with "irrelevant" traits by genetic flow with migration has been observed many times in the real world, with multiple species.Migration is at least the null model here.----- Many groups of nomads and hunter-gatherers have been seen to move unidirectionally. Consider the Hyksos and the Jurchens. Read a little about the Colonial and pre-Colonial history of Native Americans: they were constantly moving around in a decidedly non-cyclical manner, combining and splitting with each other in complex patterns.Nothing is as clean-cut as you seem to want to make it: population dynamics, ecological dynamics and evolutionary dynamics are messy. No hunter-gatherers are strictly cyclical, because they have to follow the food, and animals populations and food resources vary from year-to-year. Sometimes, they abandon some places and don't come back. This is fairly normal thing that hunter-gatherers do.It seems reasonable to expect that enough of this pattern of population movement will eventually result in some tribe or another leaving Africa. It really isn't that extraordinary an expectation.

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-Bluejay (a.k.a. Mantis, Thylacosmilus)Darwin loves you.

Hi, Bluejay; glad to see you're still with us! The evidence does not necessarily point to such a relationship. What has been found is a continuity of genetic information. A replacement (with some interbreeding) or a begetting model can both explain this. Thus, evidence of regional continuity of certain genetic material does not point to a co-existence.I hate to say this, but I'm afraid we'll have to look outside of the nucleotide for the kind of evidence that would point to co-existence. Mass, super-exodus migration, yesvery extraordinary that stuff. How could it be elsewise? I think the various oscillations of divergence-convergence cannot be explained strictly by genetic flow. However, genetic flow which is on-off interrupted due to various geographical, environmental, etc. factors can explain oscillations of divergence and convergence. Sure it has:

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Wikipedia on Selective Sweep:

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A selective sweep can occur when a new mutation occurs that increases the fitness of the carrier relative to other members of the population. Natural selection will favour individuals that have a higher fitness and with time the newly mutated variant (allele) will increase in frequency relative to other alleles. As its prevalence increases, neutral and nearly neutral genetic variation linked to the new mutation will also become more prevalent. This phenomenon is called genetic hitchhiking. A strong selective sweep results in a region of the genome where the positively selected haplotype (the mutated allele and its neighbours) is essentially the only one that exists in the population, resulting in a large reduction of the total genetic variation in that chromosome region.

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If this is the only movement you haverandom nomadic wandering that results in the occasional 'great escape', then I'd say you no longer have the movements proposed by OOA, but movements that would be more in line with an MH model.Jon

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Check out No webpage found at provided URL: Apollo's Temple!
Ignorance is temporary; you should be able to overcome it. - nwr

However, Paleo-African groups were not the densest population in Asia. Paleo-Asian groups were. If I was an early human in Asia what was the probability that I would mate with someone within the Asian population compared to the African population? I would tend to think that the odds were stronly in favor of a fellow Asian, no?The MH model requires dilution of the African genome as it is transmitted across large distances. As the Paleo-African genome is transmitted across these distances it is diluted by local variation. The density or size of the Paleo-African population is limited by the bottleneck of gene flow between populations. Geography between the continents demands such a bottleneck as exemplified by pre-Victorian economy and trade. If we treat culture like we treat genes (Dawkins eat your heart out) then why were Asian and European culture so isolated? Why was Marco Polo so revered? If these cultures were isolated even 1,000 years ago what makes you think that gene flow was unrestricted for the million years before that?

However, the "slow" expansion of a technologically advanced modern human culture that easily outcompeted human cousins would do the trick. Imagine crude H. erectus weapons that had to compete against slender spears thrown by an atlatl. It's not really fair. These human cousins would either move to other hunting grounds or try to assimilate themselves into the spreading African population.

Hi, Jon. I've never heard the term "selective sweep" before. Thanks for the new education!Still, this isn't a genome full of "irrelevant" alleles spreading through a population by hybridization: this is a single advantageous allele, plus a few "irrelevant" alleles neighboring it on a chromosome, being spread with the help of natural selection.You can't seriously say that genetic linkage accounts for 95%+ homology. The Wikipedia article you linked to says there is evidence for selective sweeps on 6 out of 23 human chromosomes. And these don't include an entire chromosome, but just small regions of chromosomes associated with single genes.You have a mechanism, but you still have no evidence that this mechanism can be expected to account for a 95% takeover by an external populationOoA has a mechanism, and there is evidence that this mechanism can, and has in the past, accounted for a 95% takeover by an external population.----- An "occasional great escape" is exactly what OoA proposes. If you want to propose that MR can absorb a "great escape" from Africa, you're just being silly.

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-Bluejay (a.k.a. Mantis, Thylacosmilus)Darwin loves you.

Perhaps our understandings of these models are different. I'm offering various alternatives that can work together to give us the same genetic layout seen presently without need of a super exodus from Africa. I am not proposing that any of these methods may have worked in isolation without input from other methods.JonEdited by Jon, : No reason given.Edited by Jon, : No reason given.

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Check out No webpage found at provided URL: Apollo's Temple!
Ignorance is temporary; you should be able to overcome it. - nwr

Huh? We're talking about the world as a whole, not just one region. And your assumption that folk in Asia just sat in Asia in complete obliviousness to the neighboring groups is nave and overly simplistic. No, it doesn't.Jon

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Check out No webpage found at provided URL: Apollo's Temple!
Ignorance is temporary; you should be able to overcome it. - nwr

The world as a whole is broken up into geographic regions with geographic bottlenecks between them which would limit gene flow. Also, mate selection is limited by migration and geography. During this time period how many woman in Asia had mates that were born in Africa? Were parents more likely to be from the same geographic area or from disparate parts of the globe?The MR model requires African DNA to move from Africa to Asia through many intermediaries. I don't know about you, but 95% of my DNA is not from my father. It is a 50/50 split between my father and mother. If African DNA must be passed from one population to the next it will be continually diluted by DNA from local populations with each generation as it moves away from Africa. What you seem to be arguing for is a type of genetic homeopathy where serial dilution in water does not dilute the drug of interest.

Hi Bluejay,I'm having trouble following where your disagreement is. I wasn't exactly sure of the differences between the OOA and MH models, so I went to wiki. Here's what it says:On MH:

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The {MH} hypothesis holds that the evolution of humanity from near the beginning of the Pleistocene two million years ago to the present day has been within a single, continuous human species. This species encompasses archaic human forms such as Homo erectus and Neanderthals as well as modern forms, which are held to be subspecies, and evolved worldwide to the diverse populations of modern Homo sapiens sapiens. The theory contends that there was some human genetic continuity in various regions of the world as well as gene interchange between the regions. Proponents of multiregional origin point to fossil and genomic evidence as support for their hypothesis.

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The primary competing hypothesis is recent African origin of modern humans (also known as "Out of Africa"), which contends that modern humans arose in Africa around 100-200,000 years ago, moving out of Africa around 50-60,000 years ago to replace the other human forms without interbreeding.
sauce

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On OOA:

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{For OOA}, archaic Homo sapiens evolved to anatomically modern humans solely in Africa, between 200,000 and 100,000 years ago, with members of one branch leaving Africa by 60,000 years ago and over time replacing earlier human populations such as Neanderthals and Homo erectus.

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The recent single origin of modern humans in East Africa was the near-consensus position held within the scientific community until 2010. However, recent sequencing of autosomal DNA from neanderthals and from an archaic human from denisova suggest that these populations, which were already outside of Africa at the posited time of the recent African human origin, also contributed to the modern human gene pool.
sauce

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It seems like you're disagreeing that the finding in the OP supports the MH model.Would you explain, again, what the problem is?

The problem is that 95% of modern human DNA across the globe is of African origin with about a 5% contribution from Neanderthals and possibly the species found in Denisova. This data would seem to indicate that the OoA mechanism is the major mechanism with the MH mechanism making a small contribution. It isn't black and white, but it is certainly tilted heavily towards one side of the grey scale.What Jon seems to be arguing is that the MH model predicts that 95% of human DNA worldwide would be African in origin due to the large population in Africa (Jon: please correct me if I got this wrong). I don't see how this can work due to restricted gene flow between human populations caused by geographic bottlenecks.