If it is true (and it seems to be) that fitness outperforms advanced levels of perception (Hoffman Theory) it is quite possible the advanced, yet extinct higher civilizations of the past simply knew too much about reality. Humanity’s greatest, enduring structures built out of natural materials—still a mystery as to how it was done. Massive complex societies gone without a trace. Perhaps the present species of humans are inept enough to outlast them through belief.
Fitness does not mean smarter. “From a biological perspective, there is no such thing as devolution. All changes in the gene frequencies of populations–and quite often in the traits those genes influence–are by definition evolutionary changes. The notion that humans might regress or “devolve” presumes that there is a preferred hierarchy of structure and function” (1)
Anthropocentric thinking has us at the pinnacle of existence (in our own minds) and maybe that persistent, false sense of superiority is our best chance at survival? It certainly isn’t a true perception of reality, but is a belief that keeps us from knowing too much, which is good for longevity.
I don’t really think we’re as smart as we used to be. The world is now full of end users led by a handful of innovators. Giza, Machu Pichu, and others, were complete societies of craftsman, artisans, engineers, and genius know how, while we are a large lot of specialists.
Following the trend in common sense it appears we have evolved to luke-warm overall intelligence with a smattering of self righteous imagination, which is apparently good for fitness.