The fact that it took eons for global evolution to generate ever larger brains implies there is an unknown factor that makes larger brains inefficient
Off the top of my head:
Larger brains are majorly useful only if you’re able to build and use tools effectively
That requires something like opposable thumbs, which few animals possess, most of which are primates
(Some animals, like elephants and whales, do have giant brains but lack opposable thumbs)
Among humans, the width of the human birth canal is the limiting factor for brain size increases (less so with Caesarean births), and we’re hitting that limit already
Not 100% sure about the above, but I think it is pretty plausible, and that it would be very premature to have high confidence in the logic you give.
Off the top of my head:
Larger brains are majorly useful only if you’re able to build and use tools effectively
That requires something like opposable thumbs, which few animals possess, most of which are primates
(Some animals, like elephants and whales, do have giant brains but lack opposable thumbs)
Among humans, the width of the human birth canal is the limiting factor for brain size increases (less so with Caesarean births), and we’re hitting that limit already
Not 100% sure about the above, but I think it is pretty plausible, and that it would be very premature to have high confidence in the logic you give.