John Hawks has posted a fascinating discussion of a new paper published in the Proceedings of the National Academy of Sciences (here) by Bedny et al. that shows that in congenitally blind adults, "brain regions that are thought to have evolved for vision can take on language processing as a result of early experience." (to quote from the abstract) (see also John Lehrer's discussion, here)
These results show the brain's immense plasticity, especially in early development. Crucially, the fact that "brain regions that did not evolve for language can nevertheless participate in language processing" (Bedny et al.) poses the questions whether language-specific processing functions need to have evolved at all.
To quote from John Hawk's discussion at lenght:
"The blind subjects tell us that the ground for language processing is almost as fertile elsewhere in the cortex. Many brain areas have the genetic equipment to recruit and organize neurons into useful circuits for language processing. Language development is developmentally robust because it can rely on a rich language environment, not because of genetic standardization. The basic problems of language evolution must be explained by showing how robust language communities emerged. I don't preclude genetics, far from it -- weaker language environments may have become stronger because of evolutionary change. But that evolution must have been substantially domain-general, because language processing is not specifically canalized by genetics.
I like this scenario because it means we shouldn't be looking for lots of language-specific genetic changes in the last few hundred thousand years. The Neandertal genome suggests that there may not have been any at all"
To me, these results also seem compatible with arguments made by Morten Christiansen, Nick Chater, and others, who argue that language was shaped by the human brain and its learning and processing mechanisms, instead of there being a language-specific biological endowment. On this view, then "language evolution is a process of cultural change, in which linguistic structures are shaped through repeated cycles of learning and use by domain-general mechanisms" (Chater & Christiansen 2010).
UPDATE [21/03/11]: John Hawks has written another highly interesting post that is also relevant to this topic and the question of the evolution of language and cognition more generally: The development of sharing and cooperation from infancy to school-age and (here).