I suspect that an evolutionary advantage of believing in free will would be motivation.
If Oog is sitting in his cave and feeling a bit peckish, he might want to go out and eviscerate a rabbit. If he’s convinced himself that his prospects are predestined, what’s the point of going out at all? He can sit in the cave and starve to death, or he can go out and get all sweaty NOT catching the rabbit. And still starve to death.
But if he can trick himself into believing that the outcome of Project Rabbit is decided by his free will, he might get to eat.
Boru
If Oog is sitting in his cave and feeling a bit peckish, he might want to go out and eviscerate a rabbit. If he’s convinced himself that his prospects are predestined, what’s the point of going out at all? He can sit in the cave and starve to death, or he can go out and get all sweaty NOT catching the rabbit. And still starve to death.
But if he can trick himself into believing that the outcome of Project Rabbit is decided by his free will, he might get to eat.
Boru
‘I can’t be having with this.’ - Esmeralda Weatherwax