More on interstratifications

There's a new paper in PNAS by J. Zilhão and colleagues which casts serious doubts on the empirical validity of claims by Gravina et al. (2005) for the presence of a Châtelperronian-Aurignacian interstratification at the site of Grotte des Fées de Châtelperron. This is the final version of a paper which was presented at the Paleoanthropology Society meetings in San Juan, Puerto Rico this past April, and John Hawks already has some good comments on it.

Empirically, there is little to argue with here, and the authors thoroughly and painstakingly debunk the evidence used by Gravina et al. (2005) in support of the alleged interstratification. They conclude that, by and large, the sequence at Grotte des Fées de Châtelperron appears to have been extensively disturbed postdepositionally and that its stratigraphy is too severely compromised for it to be used to reliably talk about the succession of Upper Paleolithic "cultures" in the area. The most damning evidence they bring to bear is the presence of typological diagnostics belonging to various technocomplexes in the layers that are at the center of the dispute. As well, there is indisputable evidence that carnivores accumulated the vast majority of the faunal assemblages of the site's levels germane to the debate, which given the dubious context of the lithics largely precludes their unambiguous association with human occupations at the site.

As concerns the lithic assemblages, they conclude that the scant number of retouched pieces relative to debitage (34.5% of the assemblage - a figure which is in actuality not all that low, but one that is consistent with the occupation of the site by residentially-mobile foragers or those on task-specific forays) and the extremely small number of Aurignacian diagnostics argue against interstratification. Most important, however, is the taphonomic study of the site's stone tools which clearly demonstrates that levels B1-3 are significantly disturbed, while levels B4 and B5 might be largely in place. Given this situation, it is more than likely, according to the authors, that the rare Aurignacian pieces (i.e., 5 pieces out of 237 total) are intrusive into B4. This is an excellent example of how taphonomic study of lithics can yield precious information about site formation processes and a further incentive for analysts to perform such studies in all contexts.

Overall, I like this paper a lot, and not only because it agrees with my colleagues and I's conclusions that Gravina et al.'s (2005) case is thoroughly unconvincing (Riel-Salvatore et al. 2006). This is the kind of critical evaluation of artifactual material that should go into any analysis of Paleolithic material, especially when dealing with such "hot button" topics as the Neanderthals' disappearance and/or their cognitve capacities. That said, as discussed in a previous post, I don't necessarily agree with Zilhão, d'Errico and their colleagues that these findings argues only for the 'indigenist' scenario of modern human origins. Considered in the broader context of Eurasia and of other kinds of interstratifications, the implications are much less straightforward than claimed in this paper. Specifically, with all the respect I have for the rigor of Zilhão and d'Errico's work and the important rejuvenation it has brought to 'Transition studies' so to speak, their perspective remains fundamentally a very culture-historical one where given artifact types can be equated directly with given "cultural" and even biological groups. While not inherently incorrect, this perspective largely discounts the fact that Pleistocene hominins made artifacts first and foremost to ensure their survival and maximize their reproductive fitness through the acquisition of the resources necessary to support them. I think that considering the transition from such an angle offers new, stimulating perspectives on the Transition that enable us to approach this evolutionary problem from the behavioral perspective necessary to cast it in the appropriate theroretical - and methodological - light.

References

Gravina, B., P. Mellars, C. Bronk Ramsey, 2005. Radiocarbon dating of interstratified Neanderthal and early modern human occupations at the Châtelperronian type-site. Nature 438:51-6.

Riel-Salvatore, J., A. E. Miller, and G. A. Clark. 2006. On the reality of a claimed Châtelperronian-Aurignacian interstratification at Grotte des Fées de Châtelperron (Allier, France). Paper presented at the 2006 Annual Meetings of the Paleoanthropology Society, San Juan, Puerto Rico.

Zilhão, J., F. d’Errico, J.-G. Bordes, A. Lenoble, J.-P. Texier, and J.-P. Rigaud. 2006. Analysis of Aurignacian interstratification at the Chaˆ telperronian-type site and implications for the behavioral modernity of Neandertals. Proceedings of the National Academy of Sciences 103:12643-12648.