That seems irrelevant to making a working brain thingy. We don't want to predict how another given brain will evolve, we want to mimic intelligence. Your brain evolves differently than mine, yet we both are intelligent (I think). I don't need to predict your thoughts to have thoughts of my own.

Perhaps the randomness is even necessary because otherwise some situations could never be resolved (like the classic who should go first to go through a door - after you - no, after you...).