The cortex/cerebellum are definitely randomly initialized at birth in terms of most synaptic connectivity[1]. The evidence for this from neuroscience is enormous, overwhelming, and by virtue of being closer to physics—trumps the weak contradictory evidence from all other softer fields (behavior genetics, dev psych, and especially especially evo psych). See this 2015 post which shows how the ev psych evolved modularity hypothesis was rather decisively disproven, and the evidence has only grown stronger since.
The cortex/cerebellum are definitely randomly initialized at birth in terms of most synaptic connectivity[1]. The evidence for this from neuroscience is enormous, overwhelming, and by virtue of being closer to physics—trumps the weak contradictory evidence from all other softer fields (behavior genetics, dev psych, and especially especially evo psych). See this 2015 post which shows how the ev psych evolved modularity hypothesis was rather decisively disproven, and the evidence has only grown stronger since.
That does not mean some low frequency components of the wiring distribution are not genetically predetermined—obviously they must be.