There's a nice post up at Thinking as a Hobby on the possibility that the brain (actually more the neocortex than brain as a whole) just isn't as complex as it may appear. Basically, the idea is that while the evolutionarily older parts of the brain are specialised, the newer neocortex is more uniform and generally generic. The question then arises as to how this generic structure gives rise to functions such as language, which only appears in the species with the most developed neocortex (i.e. us humans). The solutions are either that the assumption of uniformity is wrong, or that emergence plays a huge role (where simple rules give rise to complex behviour). A very nice thought-provoking post.
I was thinking though, from the complex behaviour as being emergent standpoint above, that this wouldn't be enough to explain something like language. The environment would have to play an overly large role on proceedings (compared to simply being a matter of brain complexity): specifically inter-human interaction, or more broadly, societies, would have to be taken into account. Essentially, the complexity of behaviour that undoubtedly exists comes from the external world rather than the internal 'rules'. The consequence of this would be that to study the emergence of language (for example), inter-agent interaction would be just as, if not more, important than the internal complexity of an individual agent. So instead of the relatively simple neocortex making things easier in terms of describing complex behaviour such as language, it would actually become more difficult, since there would be multiple concurrent levels of analysis.
Just a thought, mind, I could be missing the point :-)
Back to the beginning though, this post by Derek James is very interesting.