"After the second waiting period at the RTN corticothalamic axons shift orientation once more and invade the thalamus, a process that takes several days with most thalamic nuclei being innervated postnatally in rats, mice, and hamsters (Miller et al., 1993; Moln£r and Cordery, 1999; Jacobs et al., 2007)." [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3343305/]
Two Concepts of Constraint: Adaptationism and the Challenge from Developmental Biology Ron Amundson Philosophy of Science, Vol. 61, No. 4 (Dec., 1994), pp. 556-578 developmental constraints