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Caius -> RE: Genes Say Some Are Part Neanderthal (5/12/2010 4:25:58 PM)
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quote:
ORIGINAL: DomKen
I'll readily admit to making some assumptions but they're founded in good science. First I'm assuming that H sapiens and H neandertalis bands were male led (true of common chimps and both species of gorrila). Therefore for the cross breeding to get into and stay in our gene pool the female involved would have had to be part of a H sapiens band. This suggests that either a female H neandertalis joined a sapiens band, unlikely due to the extreme differences in diet, or that the female H sapiens bore a child from a mating outside the group. That outgroup mating was, IMO, the most likely occurence and as much as we might like the Romeo and Juliet romance the truth is likely closer to rape as weapon of war when bands of the two species were in direct competition.
Really, it would be better if you read my previous posts if you're going to continue to discuss these points with me. Many of your arguments have already been addressed in-full within them. Yes, your assumptions are founded in good science in the respect that you are applying the empirical process properly with what you know, but you are lacking some rather crucial knowledge about the particulars of...
The context in which members of these species are most likely to have met and the nature of conflict between bands (which people keep wanting to unrealistically analogize to war): http://www.collarchat.com/m.asp?m=3198031&mpage=4&key=
and
The nature of sexual selection and the rarity of rape as a reproductive strategy: http://www.collarchat.com/m.asp?m=3200189&mpage=4&key=
Yes, you are correct, these bands were almost certainly male-led, in the context of both species. Specifically they would have tended to have had an hierarchy presided over by a dominant male who had his pick of the females and would have been the final arbiter on whether new members (almost invariably female) were admitted to the group (although this hierarchy is mitigated some by the fact that this is right in the thick of the period in which we believe Homo sapiens to have begun to diversify towards slightly less polygamous mating practices). However, the male-dominant structure is exactly the reason we can expect there to have been ample opportunity for willing breeding between the two species when a female desperately (due to hunger and fear) sought admittance into a band of the opposite species after having left her own -- either because the group disintegrated or drove off excess females during a time of strained resources or because, for the sake of genetic diversity, females were prone to wander off anyway, both of which scenarios are consistent with how modern non-human primates deal with these situations and both of which are part of the accepted model of how our ancestors would have behaved -- and been granted admittance.
There's absolutely no reason to believe that the initial interbreedings couldn't have taken place in this manner -- dietary differences alone do not suffice as both species were opportunistic hunter-gatherers who clearly were able to survive in the same environments and the only notable difference that is attested to in their eating habits is that Neanderthals preferred to get the vast majority of their protein from meat. Anyway, the fact that the resulting offspring survived in such amazing numbers that they to this day account for up to 4% of the genetic material of some persons today, many tens of thousands of years after the last of these breedings occurred, demonstrates that the offspring were not at a significant competitive disadvantage in the context of the species they were raised within and thus it is unlikely the dietary needs of their 'outsider' parent were insurmountable. Consider that the entire reason that Neanderthal man became extinct in the first place was largely that they were out-competed for the food sources they shared with Homo sapiens sapiens; so not only was their shared diet considerable, but in this this context a a female Neanderthal joining a Homo sapiens sapiens group would, on average, be presented with much better eating opportunities than she would be getting in Neanderthal bands which were, bone records show, routinely suffering from mal-nutrition once Cro-magnon man came on the scene while a female Homo sapiens sapiens joining a Neanderthal band would have had considerably smaller caloric requirements than the rest of the members of the band.
Let's also bear in mind that once the initial breeding took place the resulting hybrid offspring would have been more sexually acceptable to more members of both species as females moved from group to group. Really what this new evidence does is open up the door again for the idea that Neanderthals were as much absorbed into Cro-magnon man as they were driven to extrinction by them. The interbreeding may not have even been all that rare, it could simply be a case of the specimens with more Neanderthal DNA being only so well adapted compared to their contemporaries and thus not surviving as readily to pass on their genes. Regardless, as the bands became slightly more amalgamated (and again, given the amount of Neanderthal DNA that has survived, it is fair to assume that there was the occasional region dotted with the rare band that had predominantly members who were much closer to true hybrids), then normal breeding behaviours would have been even further expected. In any account, as there was ample context for willing interbreeding we have no reason to believe rape was a driving factor in the introduction of Neanderthal genetic material into out surviving species, that it was to any significant degree more common as a breeding strategy between these species than it was within them -- that is to say, very rare compared to the more common willing mating consistent with the driving force of sexual selection. We don't need star-crossed lovers to assume this model, we simply need go with the odds.
quote:
ORIGINAL: DomKen
This doesn't hold up. We know tool styles spread rapidly after introduction. Specifically the Upper Paleolithic Revolution. We also know that H neandertalis did not adapt these new tool technologies despite lasting roughly 20,000 years past when they were introduced. That's an awfully long time during which the same basic tool tech spread throughout H sapiens but made no inroads in the other species. Clearly H sapiens traded, including knowledge, and clearly this trade did not include H neadertalis.
Trade in the sense of actual commerce (the exchange of goods and technologies via bartering) was, at the very most, a relative rarity. The tools spread 'rapidly' only in in the sense that they spread more quickly than their precursors in Homo sapiens sapiens' forerunners. The tool-lore, what little of it was not innate to the human brain by this point, was inherited (in the educational, not genetic, sense) and to some limited extent spread by members slowly migrating to other bands, these three factors (innate knowledge, spread of the species, rare occasion of a new member bringing her native band's neat new little trick to a new group) more than capable of accounting for the 'rapid' spread of these tools in the context of tens of thousands of years. Regardless, Cro-Magnon left Africa and migrated into Neanderthal lands (the Near East and Europe) already possessing the majority of its tool-fashioning capability. Also note that the Great Leap Forward is a concept of some uncertainty and fraught with debate even amongst it's adherents, so we have to be careful about adding it to our empirical treatment of this subject, though mind you I agree with the likelihood of many of its elements. Anyway, the inability for Neanderthals to acquire this knowledge says nothing about Cro-magnon exchange of ideas; Neanderthals were simply incapable of adapting these technologies, as is evidenced by the fact that they lived in the same environment for hundreds of thousands of years and never adapted their precursor technologies the way Homo sapiens sapiens did. On a side-note, 20, 000 years may be a little on the high-side for the period we now expect the two species to have co-existed together. In fact, it might be twice the amount of time it took Cro-magnon to drive them into extinction/absorb them to some small degree, if you accept the most recent models. I still tend towards the more neutral 15, 000 years, but then, clearly, I'm a consensus builder. ;)
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