Update III: John Hawks comments.
Update II: Here is the paper. The abstract:
A common assumption in the evolutionary scenario of the first Eurasian hominin populations is that they all had an African origin. This assumption also seems to apply for the Early and Middle Pleistocene populations, whose presence in Europe has been largely explained by a discontinuous flow of African emigrant waves. Only recently, some voices have speculated about the possibility of Asia being a center of speciation. However, no hard evidence has been presented to support this hypothesis. We present evidence from the most complete and up-to-date analysis of the hominin permanent dentition from Africa and Eurasia. The results show important morphological differences between the hominins found in both continents during the Pleistocene, suggesting that their evolutionary courses were relatively independent. We propose that the genetic impact of Asia in the colonization of Europe during the Early and Middle Pleistocene was stronger than that of Africa.
Update: National Geographic has a better article up. From reading it closely I think the authors are suggesting that the ancestors of what became the Neandertals were derived form Asian hominid populations. If later Africa hominids, anatomically modern humans, replaced this population around 50,000-30,000 years ago then that sector of the "bush" was pruned.
This article in a Turkish newspaper summarizes a report which will be out in PNAS in a few days that speaks to the relationship between various recent human lineages through dental morphology. The headline is "Study points to larger role of Asian ancestors in evolution," but the article is pretty garbled and I don't really trust it to be accurate about what it's representing, so best to wait for the PNAS paper. In any case, I do think it is important to be cautious about translating morphological continuity as clear and present evidence of genetic continuity in any preponderant fashion. The reasoning is simply that trivial admixture can result in the uptake of adaptive features rather quickly so that a new population can morph so as to match the optimal local ecotype. For example, Polar Bears seem simply to be a local derived variant of Brown Bear. Genetically there are Brown Bear subspecies which are closer to the Polar Bear than they are to other Brown Bear subspecies!
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In the case that you get news of the actual publication first, do you mind sharing with me the link to the paper? Other news sources say it's come out today, but I've checked the PNAS early edition, and no luck.
Thanks,
Kambiz
crap always goes up on their site later than what they tell the press. in contrast, some journals push things to their RSS days before they rebuild their site links, so you're stuck with just the abstract for a while ;-)
It seems that the NG article is talking about migration patterns of pre-modern humans and not of homo sapiens. If I'm not mistaken (I'm not a geneticist) the genetic data gathered so far for Homo sapiens shows a pretty clear migration to the middle east and then up to the caucuses and toward india and then a kind of curve back toward Europe. And there were at least three probably four separate migrations of Homo sapiens into Europe since the last Ice Age. _Before the Dawn_ has a pretty great summary chapter on the genetic evidence of migration, but I'm not sure how up to date it is, and it treats only Homo sapiens.
todd,
your summary is a good first approximation except one minor pedantic point: it is homo sapiens sapiens. that is, neandertals are homo sapiens too, homo sapiens neandertalis. the whole period between erectus/ergaster and modern humans is put into a grab-bag of 'archaic homo sapiens.'
Razib,
Methinks your definition of 'species' is a bit restricted. There are cases where different species do interbreed under certain conditions. Wolves and coyotes for example. (Or wolves and dogs according to those who put an emphasis on certain differences the mainstream tends to overlook.)
Remember, sometimes it's not how much the two species differ, it's how the two species differ.
there is no 'real' definition for species. itz all instrumental dog....
Again, admitting my amateur status in discussions of human evolution (i.e., relatively well read, but not formally trained), I've never seen Neanderthals referred to as Homo sapiens neanderthalis, only as Homo neanderthalis. Homo sapiens seems in the stuff I've been reading lately to refer to modern humans prior to "the great leap" (ca., 50,000 ya), that is, morphologically modern but without the cultural trappings that we think of as "human." And Homo sapiens sapiens seems to refer to modern humans w/ complete language, symbol systems, rudimentary agriculture and ultimately complex social formations.
Of course these are all fluid names as our knowledge is still pretty vague at this point (e.g., whether or not Neanderthals and modern humans interbred). In any case, I get your point and the distinction you're making, regardless of the nomenclature.
Per the study itself, I agree with Hawks's critique and feel like I may be getting this stuff finally, as that was the critique I had as well. [I say that fully cognizant that it adds nothing to the discussion other than a "Me too!" from the back row.]
todd,
systematics isn't my deal, and i'm not really interested in it in detail. but there is wiki:
For many years, professionals vigorously debated about whether Neanderthals should be classified as Homo neanderthalensis or as Homo sapiens neanderthalensis, the latter placing Neanderthals as a subspecies of Homo sapiens. However, evidence from mitochondrial DNA studies have been interpreted as evidence that Neanderthals were not a subspecies of H. sapiens.[7] Recent genetic simulations suggested that 5% of human DNA can only be accounted for by assuming a substantial contribution of Neanderthaler to the European gene pool of up to 25%.[8] Some scientists, for example Milford Wolpoff, argue that fossil evidence suggests that the two species interbred, and hence were the same biological species. Others, for example Cambridge Professor Paul Mellars, say "no evidence has been found of cultural interaction".
Adding fuel to the discussion, here is the results page at Gigablast on the keyphrase savannah cat.
In short, a cat breeder crossbred domestic cats with servals. Most attempts failed, and of those that succeeded the kittens were sterile. But he did get fertile hybrids, enough to then take the animals and breed them to domestic cats. After a few generations he had a distinctive breed which now commands a fair amount of change in the exotic breeds business.
It's not an all or nothing thing. Sometimes you have the wolf/coyote situation where hybrids are virtually garanteed. then you have the majority of situations where nothing results. But sometimes you get a serval/domestic cat one where most attempts fail, a few produce mules, and a very few give you further breeding stock.
It could be that humans and neanderthals had limited interbreeding capability. Most would fail, a few prodce mules, and a very few fertile young. I have more thoughts on this matter, which may go up at my blog.
allan, make sure not to use bird examples ;-) they got no placenta, so speciation 30 million years ago isn't necessarily a bar to hybridization.