Neanderthal-sapiens relations: more ‘Brady Bunch’ than ‘Family Fued’
In a previous post, I briefly discussed the notion of a speciation reversal and how this could be seen to have applied to the rejoining of the phylogenetic branches of Homo neanderthalensis and Homo sapiens some time between 50 and 25 thousand years ago (not a discrete event of course, don’t bite into that particular serpent’s apple, it would have occurred gradually). In an update at the end of that post, I mentioned a paper that seemed to support a similar point of view to some degree. The paper is cited below:
Barton, C. M., & Riel-Salvatore, J. (2012). Agents of Change: Modeling Biocultural Evolution in Upper Pleistocene Western Eurasia. Advances in Complex Systems, 15(1-2).
Utilising some interesting computer models, Barton & Riel-Salvatore have argued that rather than being overwhelmed and ultimately destroyed by their technologically/culturally superior cousins, Neanderthals may well have disappeared as a result of something slightly less intuitive. It was argued that it was the roughly equivalent level of cultural sophistication in Neanderthals that spelled their doom as a distinct species. I saw the double take you just did, let me explain. If the Neanderthals were in possession of a highly adaptable culture that ultimately provided adaptive solutions to the fluctuating climate of the middle-late Pleistocene AND were biologically capable of mating with anatomically modern humans (AMH), would not their adaptive behaviour have eventually pushed them into increasing contact with the equally culturally adaptable new arrivals, resulting in cultural exchange and eventually hybridisation to the point of non-existence of the smaller population? Kazaam! Speciation reversal!
This idea is offered further weight by a paper published in Molecular Biology & Evolution in late February, see below:
Dalen, L., Orlando, L., Shapiro, B., Durling, M. B. m., Quam, R., Gilbert, M. T. P., et al. (2012). Partial genetic turnover in neandertals: continuity in the east and population replacement in the west. Molecular Biology and Evolution.
Essentially, based on molecular evidence, Dalen and friends argue that prior to exposure to AMH, Neanderthal populations were likely to have been in decline already, having lost a large proportion of their numbers (and genetic diversity) to aforementioned Pleistocene climate instabilities. The simple truth is, no matter how culturally clever your species, an ice-age poses incredible ecological challenges that are likely to dwindle the numbers of any animal attempting to weather it. This saw the smaller remaining Neanderthal populations migrating southward toward more habitable lands, right into the path of AMH, expanding north from their much more hospitable sub-tropical birthplace. If Neanderthal numbers were low enough, this may have made mating with the biologically compatible and more plentiful AMH the only viable survival strategy. There is even a certain logic to arguing that this may have been both culturally and biologically advantageous to AMH. Ultimately, the smaller contributor to any given enduring admixture will eventually be consumed, resulting in a more homogenous population overall (the new hybrid species).
While I have no doubts that some conflict was likely between groups of AMH and Neanderthals, given the above I would be more inclined to say that their meetings were more cordial than that. I would love to hear what any readers might think of this, especially those of you with a finger in the paleontological pie.