> Is there a level cap for fish intelligence where an individual fish won't gain any more benefit from increased intelligence?
Think of it this way: intelligence has costs (metabolic, anatomical, etc) as well as benefits. At some point, costs outweigh benefits. That point is highly dependant on environment.
You’re missing out on societal costs as well. We as humans needed civilizations, eg farming, where one person could cultivate more than one persons food thereby freeing up time for others in the community to work on other things. If a community doesn’t have that the cost is too high to let one person whittle away days trying to invent.
> The size of the neonatal skull is large relative to the dimensions of the birth canal in the female pelvis. This is the reason why childbirth is slower and more difficult in humans than in most other primates.
Think of it this way: intelligence has costs (metabolic, anatomical, etc) as well as benefits. At some point, costs outweigh benefits. That point is highly dependant on environment.