> 1… But given that more intelligence requires more brain mass, which results in more metabolic costs, one would expect us to have the lowest possible level of

> 1… But given that more intelligence requires more brain mass, which results in more metabolic costs, one would expect us to have the lowest possible level of abstract intelligence required for surviving in the precise ecological niche in which Homo sapiens developed: the barest minimum intelligence needed to scrape through a few million years of hunting and gathering until we got lucky and stumbled into the Neolithic Revolution. This is atomically reductive to the point it loses the point of the question. Humans are social creatures, not individual calorie expenditure calculations. Groups of early, successful humans had different needs. Broadly, they needed workers just smart enough to complete tasks, warriors with exceptional physical characteristics, and a class (typically ruling) with higher cognitive function to keep the society organized and to protect it from existential threats. The size and complexity of the group is limited not just by the ruling class’s cognitive function, but the baseline populations’ ability to conform to more complex social structures. Larger groups can conquer smaller groups, creating an evolutionary advantage for groups that produce occasional individuals with much higher cognitive function, and a baseline level of cognitive function to maintain a cohesive tribe. This forms the basis of culture and tradition, which create a reinforcing evolutionary bias for higher cognition that can extend past many generations as well, where individuals with exceptional cognition have more offspring, because the characteristic is viewed as exceptional. You’ll find evidence of this in religious texts like the Torah. It’s a survival mechanism.