Comments on: Modern Humans and Neanderthals: Did they”do it?”

By: Justin Moretti

Justin Moretti — Mon, 19 Nov 2007 15:56:35 +0000

Yes, but imagine the practical attractions of a partner with whom sex can be guaranteed never to produce any viable offspring. And as for the butt-ugly, I'm sure kinks existed even back then.

By: Fred

Fred — Mon, 19 Nov 2007 13:11:53 +0000

I’m no expert, but being a modern homo sapien, I find Neanderthals butt-ugly. I suspect my forbearers did as well.

By: Warren

Warren — Mon, 19 Nov 2007 11:57:02 +0000

Consider the number of people who continue, today, to “do it” with nonhuman animals. Did our ancestors do the same with Neanderthals? Heh, well.

By: cuchulainn

cuchulainn — Mon, 19 Nov 2007 09:32:25 +0000

right, presumably africans didn’t interbreed with them. does that make the races different species?

By: greg laden

greg laden — Mon, 19 Nov 2007 07:49:20 +0000

By the way, here’s John’s Paper:http://www.paleoanthro.org/journal/content/PA20060101.pdf

By: greg laden

greg laden — Mon, 19 Nov 2007 07:48:13 +0000

Razib: Adaptive introgression (or just introgression, really) is the transfer of alleles from one population to another where there is usually separation. In mammals this is expected to happen in relatively closely related species.Assume Neanderthals and contemporary moderns have a divergence of about 0.5 mya. Now, you look at a segment of the genome where you suspect there is an “introgressive” allele. You somehow statistically figure out that there is an allele that is shared with a very low probability … in other words, this gene has alleles with a coalescence point that is subsequent to 0.5 mya (so the allele likely arose in one lineage) and the base pairs match exactly (so it looks like it “transferred).There are three explanations that have to be considered:1) You are not really seeing anything, it is the product of chance. The info provided above suggests that this is unlikely but it is possible.2) The allele is similar because of common ancestry; and3) The allele “introgressed” (by whatever mechanism that is supposed to happen).If the difference between the coalesence for diversity in this allele in the donor population is recent, and the split between the two populations is old, then 2 is very unlikely and 3 is more likely. As the coalesence for the alleles for this gene gets older and/or the split between the lineages gets younger, 2 becomes more likely and 3 becomes less likely.Also, for any divergence point, you’ve got to figure on biogeographical grounds alone there is some fuzziness, but the fuzziness remains stable as the divergence extends back into the past. In other words, there is a fixed period of time during which there is a lot of gene flow, then once that “stops” and time continues marching on, that becomes a smaller and smaller percentage of the total divergence time and becomes less important.With a divergence time of 0.5 mya, and a lot of biogeographical overlap, I would assume that this period of increased gene flow is a large percentage of that time (maybe 10 or 20 percent?).Therefore, the choice between options 2 and 3 is pretty unclear. That’s what I meant.

By: razib

razib — Mon, 19 Nov 2007 01:44:40 +0000

RPM: Maybe, but since we are talking about very spotty data derived from individuals all of whom are members of the same species, most likely, this is not too impressive. The divergence between N's and amHS is much MORE impressive.could you unpack this for me? i mean, isn't the adaptive introgression inference based on very long and deep branches which are pushed back beyond the neandertal-human separtion or around thereabouts?

By: Azkyroth

Azkyroth — Mon, 19 Nov 2007 01:04:08 +0000

All I have to say that if Neanderthals and modern humans never interbred, certain of my former classmates demand an alternate explanation…

By: Greg Laden

Greg Laden — Sun, 18 Nov 2007 14:34:52 +0000

Martin: One could never say that you were anything other than not at all in correct.RPM: Maybe, but since we are talking about very spotty data derived from individuals all of whom are members of the same species, most likely, this is not too impressive. The divergence between N’s and amHS is much MORE impressive.

By: Anne Gilbert

Anne Gilbert — Sun, 18 Nov 2007 14:20:18 +0000

The question of "did they or didn't they" is much more complicated than it would appear to be. First of all, a note on the studies themselves: all the writes of these papers, no matter what "side" they come down on regarding this issues, have a priori assumptions(perhaps largely unconscious), that tend to affect the questions they ask, the methods they use, or the "framework" of the research. As you probably are aware, you can get different results from measuring the same fossil material, depending on what methods of measurement you use and the questions you ask. And note well: I'm not letting any "side" or paleoanthropological/archaeological faction off the hook here. So these studies mean b>something, but exactly what they mean is as yet unclear.Second, it's my understanding that the Cioclovina fossil is a "modern" human, with purported Neandertal traits, not an actual Neandertal, though I may have misread the studies on this. So if Neandertals and "moderns" interbred in this particular part of their overlapping range, it wold be quite natural for some early "moderns" to have "Neandertal traits". After all, there doesn't seem to have been anything to prevent such interbreeding, as far as their respective behaviors were concerned; at least that's what such archaeological evidence as exists, tells me. Culturally, it's another question, but at this time period, whether we're talking about early "moderns" or late Neandertals, there's no way of telling.Finally, given the (probably) low numbers of both populations, in and around Cioclovina and everywhere else in Western Eurasia at the time --- and Neandertals may have been a very small population indeed ---it isn't too surprising that contemporary "modern" populations don't seem to have any "Neandertal genes"(what is a "Neandertal gene", anyway?). As a population, "modrn H.sapiens is 6 billion strong and counting. . . the mahhematics from 30,000 years ago until now, just don't favor that kind of surivival. But again, that's another story.Anne Gilbert