In this paper (2013.Miller.etal.otolemur.myelin.ache.development), published in the Journal of Comparative Neurology (2013), we explored the idea that the primate nervous system might be different from other mammals in the development of the auditory system, which gives rise to vocal behavior and, in humans, language. We quantified the amount of myelin, and the expression profile of acetylcholinesterase in the brainstem, thalamus and cerebral cortex (see picture) of the prosimian primate (Otolemur garnetti).

Our results suggest that beginning during gestation, the primate brain processes auditory information differently than has been reported for rodents and other mammalian species.

These data are interesting in that they suggest basic mechanisms (neuromodulatory molecules, like the picture) by which vocal behavior might be modified over the course of evolution, and may be important in the development of language in humans.