Just read a dynamite paper by Erella Hovers, a chapter in Conard's When Neanderthals and Modern Humans Met (2006), about the nature of interactions between the two hominin groups in the Levant. She focuses mainly on the Middle Paleolithic record of the region. After reviewing the available empirical evidence and discussing relevant ecological theory, she concludes that:
"Some archaeologists have favored [the competitive model] as the most ecologically parsimonious scenario (Shea 2003b), given the principle of competitive exclusion. However, the Levant in the late Middle and early Upper Pleistocene was a region of unpredictable, short-duration environmental fluctuations on millennial and centennial scales, and of spatially fragmented habitats. Because the coexistence of similar species does not depend on environmental stochasticity (Wang et al. 2000), and since Neanderthals and modern humans were congruent competitors in this region, a scenario of their coexistence in dynamic equilibrium on a regional scale is tenable from an ecological point of view. And while full synchrony of Moderns and Neanderthals throughout the Middle Paleolithic (or at least its later part) is not a fact of the archaeological record, a scenario of coexistence is as, or more, consistent with the available data than a model of competition-driven extinctions of the two taxa. The suggestion that Neanderthal appearance and the disappearance of Moderns are linked by a cause-and-effect relationship is not well supported by either the archaeological data or ecological theory. It stems from confounding temporal association of postulated events with causation for long-term demographic and evolutionary processes. Indications (and putative ones at that) for local extinctions of Moderns (or Neanderthals) during the Middle Paleolithic cannot be simplistically be interpreted as evidence for the extinction of a whole lineage in the region" (Hovers 2006:76)
This is a pretty radical departure from commonly proposed scenarios of Neanderthal-modern human interactions in the Levant. What I especially like about this paper is that Hovers actually reviews the ecological literature in this piece rather than simply invoking it as a mysterious black box buzzing with the sounds of arcane evolutionary forces to support her ideas. By doing this, she's able to generate coherent sets of theoretically-grounded expectations that she then tests against the archaeological record, as opposed to the other way around which is how at least some archaeologists tend to proceed. The kind of approach adopted by Hovers here is the way to go, in my humble opinion, if we are to move the debate over the evolutionary fate of Neanderthals forward.
Conard, N. J. (ed.). 2006. When Neanderthals and Modern Humans Met. Tübingen Publications in Prehistory. Kerns Verlag, Tübingen.
Hovers, E. 2006. Neanderthals and modern humans in the Middle Paleolithic of the Levant: what kind of interactions. In When Neanderthals and Modern Humans Met (N.J. Conard, ed.), pp. 65-85. Tübingen Publications in Prehistory. Kerns Verlag, Tübingen.