Watching a video on the uses of evolution to generate artificial intelliegence, I had a click in my head. The video had a segment about the average brain complexity over time. The brain complexity went up then had a hump and then plateaud out a little lower. The speaker agreed with someone in the audience that one reason that the AIs may have become slightly less complex after their hump of high complexity would have been because they evolved to be as complex and no more complex than necessary to survive well. Then they surmised that the complexity of the environment affects the complexity of the entities in it.
I can see how this works today too. We evolved from bacteria to some mammalian form over a long period of time, and the mammalian form was as complex as necesary at that time. From that form to the living in groups form that we have now, the complexity of the environment has been adjusted by not only outside affectors like other life forms, but also inside ones too. The first breed of altruists lead us to a better genetic victory, but altruism brought a new layer of complexity to the world for those that worked in it's circle. It became necessary to remember those that have repaid, those that cheat, how to cheat without being found out, how to survive novel circumstances, and probably more. The complexity of the new environment may not actually be a new and more complex physical environment, but the required brain complexity for thriving survival got bigger and bigger, like an arms race of intelligence, religion and honour systems springing forth to add some reduced complexity controls, and people following others so their brains can be artificially bigger.
So, are we intelligent because we are only as intelligent as we need to be, in a complex environment made from our own intelligence which was driven by the inherent complexity of living as a group?