New Type of Ancient Human Found—Descendants Live Today?

Hi, CS. Sure thing. I've actually got two different disagreements going on: one with the multiregional hypothesis, and one with Jon.My disagreement about MR is primarily just a semantic one: I agree that there is some genetic diversity in modern humans that clearly didn't come from African H. sapiens; but this explains such a tiny percentage of the data that it hardly seems meaningful to me to try to rewrite the paradigm as a compromise between the two competing theories because of it. It makes more sense to me to just let OoA assimilate the idea that there was some small amount of genetic admixture.That disagreement isn't particularly important to me: you'll see that I haven't put a lot of effort into following up on the responses I've gotten about it. I'm perfectly happy to drop it, in fact.-----The main disagreement I have is with Jon's proposal that the available evidence doesn't point to a directional migration of people out of Africa. So, he's not arguing, like Nuggin, that both OoA and MR are correct: he's turned a minimal vindication of one of MR's claims into a strong challenge against the core of OoA.Jon is convinced that movement of paleo-Africans over great distances is an extraordinary claim, and that we are thus in need of some other mechanism that doesn't involve any people walking outside of their normal habitats. Trace amounts of Neanderthal and Denisovan genetic signatures in some human populations is enough for Jon to decide that we no longer need to resort to such outlandish claims as nomadic hunter-gatherers moving into new territories.I'm trying to reason with him that movement of nomads into new areas isn't really such an outlandish claim, and that his alternative proposals are much more dubious.

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

Hi, Jon. Probably an understatement.----- And, in the meantime, I'm showing you that the movement of nomads into new areas isn't nearly so outlandish that we need to be coming up with various ways to avoid having to resort to it

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

Hi, CS. Sure, I'm always open to discussing things with someone who wants to discuss them.----- I tend to agree more with Taq's mechanistic approach. It seems silly to me to formulate a theory about biology---a field in which essentially all data sets are messy---so that it can't tolerate any deviance from 100% purity.This seems like what the new MR-proponents are doing: they're arguing that any deviance from the most stringent interpretation of OoA is vindication of MR.----- What's happened here is a kind of distillation of the two theories into pure principles. But, neither one was really a "pure principle" to begin with.MR was specifically the idea that H. erectus, Neanderthal and Africans were all the same species, and that each population evolved in partial isolation into the regional varieties of human that we see today (i.e. African, European and Asian), although they were not isolated enough to break the general continuity of the species that we see today.MR has been resurrected in principle because a trace amount of admixture was found. This admixture doesn't actually explain any of the evidence that MR was originally proposed to explain (e.g., the morphological features shared by H. erectus and modern Asians), and doesn't really demonstrate what the original MR proposed.So basically it's a redefinition of MR as any model proposing that somebody, somewhere, has a non-African ancestor; which accordingly redefines OoA as any model proposing that nobody, anywhere has a non-African ancestor.I don't think this is a fair interpretation of either theory. And, I think it's certainly abnormal to propose that a scientific theory included a universal negative statement as one of its core claims.But, in the end, we're just debating about what to call the paradigm, rather than debating the principles and concepts involved, so it's not something I'm going to get rabid about.

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

Hi, Jon. I don't think anybody assumes that migration is the only explanation: we all conclude that it's by far the best explanation. That's all science ever does.Theoretically, selective sweeps and passive diffusion could very well cause a population to reach 95% homology with a different population. I'll grant you that theoretical possibility. But, realistically, given our actual observations of hybrid populations and selective sweeps, it's highly dubious, at best.

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

Hi, Jon. I think I've already described the grounds on which I, personally, make this conclusion. Remember that stuff about "no non-migration explanation has yet been demonstrated to have caused such evidence as we see" and "there are numerous cases in which immigration models, with or without genetic admixture, have caused population turnover"?Remember that stuff?I think that was pretty good stuff, but that doesn't mean I want to just repeat it all over again.

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

Hi, Jon. Not true: humans have been moving around and migrating quite extensively. Again, I refer you to the Hyksos and the Jurchens and the Native Americans. These are groups of people that are famous for mass movements.And, there are migrations that are better documented than those: Celtic peoples used to live all across Europe. In the first few centuries AD, the Germanic peoples migrated across Europe from the North and displaced the Celts. A few hundred years later, the Slavic peoples also migrated into Eastern and Southern Europe from Siberia or Ukraine (there are competing theories). And, don't forget the Vikings.How about the Moors? They invaded Spain from northern Africa in the Middle Ages, and their descendants are still there.How about the Romani? They live all over Europe.In the 1700's and 1800's, the Russians expanded northward, eastward and westward, taking over Murmansk, Siberia and parts of the Baltic.That's just off the top of my head, and I'm not even a historian. If I were given time, I'm sure I could list dozens more large migration events like these.----- Speciation isn't really even an issue here: divergence has clearly happened, as evidenced by haplogroup distribution among different regional populations, and by the occasional observation that some races respond differently to medications, and by features like Coyote mentioned (the characteristic incisor shape of Asians). True, it's doubtful that regional populations of humans even warrant subspecies designation, but this is pretty immaterial to the whole point.

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

Hi, Jon. Are all arguments against OoA to be based on claims that OoA relies extensively on a notorious scientific faux pas?Universal negative claims and arbitrarily-defined terminology are very strange criteria for scientists to use as the bases of major scientific theories, wouldn't you agree?However, you seem hell-bent on overturning a remarkably successful theory of human origins based on exactly such criteria. Even if OoA was originally formulated to include a universal negative claim ("nobody, anywhere has a non-African ancestor") and even if it was strictly dependent on H. sapiens, Neanderthals and Denisovans being distinct species based on the biological species concept, what is your objection to simply letting it relax these assumptions?We do this all the time in science. Theories change over time. They're supposed to change. We get no where by coining a theory as "any deviation from that other theory," because then we end up in an absurd situation of rejecting OoA simply because it didn't meet somebody's semantic criteria for the words "species" and "migration," and because it got shoehorned into a crotchety absolution.By parallel, consider this:Would you argue that the theory of universal common descent holds that no organism did not evolve from the first life-form on Earth?
Would you then argue that any of the following would require us to entirely reject universal common descent:

1. Discovery of alien life not related to earth life
2. Discovery of a life-form that was unequivocally created by God
3. Successful creation of a novel type of life-form in the laboratory
4. Discovery that some life on Earth fits into a separate tree of life that traces to a different common ancestor?

Or, would you agree that a simple relaxation of the "universal" part would suffice?The point is that the out-of-Africa migration happened. This is evidenced by remains of anatomically modern humans that coexisted with anatomically-distinct Neanderthals in Israel up until about 60,000 years ago. It is also evidenced by the switch from genetic divergence to genetic convergence between populations around the proposed time of the out-of-Africa migration, by the dominance of the gene pool by the African lineage of humans, and by the continued pattern of human migration as an important component of population genetics.It is contested only by a proposed mechanism for which there is little, if any, evidence in the remains of hominids, and which has no precedent as a explanatory mechanism for such a broad-scope phenomenon as it is being proposed to explain.Spurious demands for conformity to a specific definition of "species" for each isolated population, and discovery of trace amounts of interbreeding do not serve as evidence against an ancestral migration out of Africa.Whether we eventually decide to change the name of our paradigm from "Recent African Origin" to something that more suitably acknowledges the minority role of genetic admixture is immaterial to me. What is important to me is that we not overturn a very successful paradigm based on whimsical population genetics models and trace evidence that can be easily assimilated into the current paradigm.

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

Hi, Jon. To the point where we realize that evidence of interbreeding is not a valid reason to question whether or not there was an out-of-Africa migration.----- To the point where we realize that there really isn't that great a difference between a 100% explanation and a 95% explanation.

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

Hi, Jon. It becomes a non-point, because, after hybridization is assimilated into the migration model, the alternate theory has no verified predictions that aren't already contained within the current, successful model.This is important, because the ideas of "an out-of-Africa migration" and "no hybridization with other hominids" have become so conflated as to cause people to think evidence against one is also evidence against the other. They are, in fact, two separate claims, and either one could fall without bringing the other down with it.When we permit the out-of-Africa model to allow some hybridization, we avoid conflating evidence of interbreeding with evidence against migration.Opponents of OoA are ready to jump all over the model as a whole because one of the more dubious claims associated with it was defeated. It's like failing to beat one's opponent in the ring, and then declaring victory over the whole team after shooting his pet dog in retaliation.----- It gets us to realize that we don't have to overturn an entire successful model on the basis of a tiny deviance from the model's expectations, even if that tiny deviance is in the direction expected by an alternate model. It gets us away from the idea that a tiny hiccup in a scientific theory is a silver bullet.

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

Hi, Jon. But, you've been arguing as if it does. You've presented several reasons why it's more compatible with a diffusion/hybridization model than it is with a migration model.Sure, "disprove" is probably too strong a word for what you've been arguing, but you have been using it as the key component of a case against OoA. I'll amend my previous analogy to the following:

quote:

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It's like failing to beat one's opponent in the ring, and then calling it a draw when you go shoot his pet dog in retaliation.

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----- But, does it really verify a prediction made by MR? Look at it more realistically: did MR predict admixture, or did it predict substantial amounts of admixture? Realistically, 5% of one exceptional regional population doesn't verify anything except the most skeletal, minimalistic interpretation of MR.For all intents and purposes, MR is essentially useless as an explanatory model for the ancestry of modern humans. There's no real call to resurrect it over 5% of one unusual population.

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

Hi, Jon. Modern Asians are only descended from Homo erectus to the extent that they inherited traits from them. Subsequent evolution that may have happened along the proposed H. erectus-Asian lineage is taken into account when these analyses are done, so, as far as I am aware, this is not a serious confounding factor for this type of analysis.----- But, we also don't expect the daughter varieties of one ancestor to be identical to the daughter varieties of a different ancestor. If MR is to explain the differences between regional populations (as it's supposed to), then those differences should be inherited by modern humans from the ancient humans in the same region, with or without mutations.And, there is currently extremely sparse evidence for this.----- A model that only explains 5% of the data is not essentially useless? Why not?

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

Hi, Jon. You're mincing words, Jon. If there is no resemblance between modern Asian and ancient Asian populations, then what, exactly, is MR meant to be explaining?How on earth do you draw a distinction between the "degree of regional continuity" and the "degree of contribution of older regional populations"? What is continuous about them if not the traits that came from the older populations?OoA and MR are hypotheses about the actual, genealogical descent of modern humans. "Regional continuity," as claimed by MR, refers to genealogical descent from older regional populations, which entails genetic contributions to the modern regional gene pool. Otherwise, MR is not a hypothesis about the descent of modern humans.

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

Hi, Jon. As Kapyong explained beautifully here, a theory in science is an explanation for something. This can be extended to a hypothesis, as well.So, what are OoA and MR supposed to explain?You seem to be going down the path that MR is just the hypothesis that modern humans interbred with other groups of Homo. This is not accurate. The reason MR comes into conflict with OoA is because both are hypotheses that attempt to explain the ancestry of modern, living humans, not just claims about whether some particular event (migration or hybridization) happened in prehistory.So, the amount of evidence that remains to the present day is precisely the thing that the hypothesis is meant to be explaining, and is thus a direct measure of the correctness and explanatory power of the two hypotheses.If an out-of-Africa migration is demonstrated to have happened, but nobody today is descended from the migrants, then OoA is falsified.
If interbreeding among various groups of Homo is demonstrated to have happened, but nobody today is descended from the hybrids, then MR is falsified.Because there is evidence demonstrating that both happened, and that people today are descended from both migrants and hybrids, we allow the predominant mechanism to dominate our paradigm. Thus, OoA remains the champion, with a minor contribution from MR.

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

Hi, Jon.

1. Then please illustrate for me what else these two hypotheses are meant to explain, other than the ancestry of modern humans.
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2. There are no nuances to the term "ancestry"; and, even if there were, none of them is relevant to this debate.

----- You see this because you think any model that is "technically not impossible" is equally capable of explaining the evidence as any other model. Therefore, when you see some farfetched idea about population genetics that can accommodate the data, you automatically assign it the same value and explanatory power as a more realistic and straightforward model.It's official: this discussion has turned me into Straggler. That is my cue to get out while I can. I deem you hopeless anyway. Unorthodoxy seems to be a hobby with you, and there is nothing to be gained by trying to get you to accept the orthodox view of anything.----- The person who wants to believe his theory will never see any evidence that can definitively corroborate the opposing theory.

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

It's been several months since Jon and I ruined this perfectly decent thread about human ancestry. I have not intention of resurrecting it just to ruin it again, but a new paper has emerged with some new genetic information that provides new insights into the controversy. Here is a link to the abstract. The authors of this study have uncovered a segment of DNA from the human X-chromosome that is present as a minority in all modern populations outside of Africa. This segment can apparently be traced to a Neanderthal origin, and is present in about 9% of the sample of over 6000 multinational humans tested.These researchers explain this data as evidence for an early admixture between African humans and European Neanderthals, prior to the spread of the predominantly African group across Asia.This data, combined with the earlier discoveries of minority Neanderthal and Denisovan haplotypes in various populations around the world, provide support for the Multiregional Hypothesis of human origins. It is seeming more and more likely now that early African Homo sapiens did interbreed with various other populations of hominids in different parts of the world.My personal view remains that the Out of Africa model explains the majority of modern human ancestry, and should not be regarded as falsified by this information; however, I also accept that the strict OoA model is insufficient to explain human ancestry. A hybrid view involving both an out-of-Africa migration and significant regional interbreeding is currently the best explanation for human ancestry.

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