The order in which different brain areas reach maturity must be crucial to how activity-guided development creates functional specialisation (there’s good stuff on this in Rethinking Innateness). Here’s a maturational timetable (via) for different brain areas:
Notice that it’s areas associated with audition that finish myelination first (in the womb), and the neocortex which finishes last (about 25 years later).
Elman, J., Bates, E., Johnson, M., Karmiloff-Smith, A., Parisi, D., & Plunkett, K. (1996). Rethinking innateness: A connectionist perspective on development. Cambridge, MA: MIT Press/Bradford Books.