Permit me to dumb this down a little.
1. Biological variation within humanity (human bio-diversity aka HBD) and correlating cultural diversity may include diversity of psychological baseline health.
2. If this is true, then there may be psychological conditions that are healthy for an individual depending on that individual’s environment.
3. Such psychology would be adaptive for some conditions, and therefore sane, but mal-adapted for other conditions, and therefore insane.
4. Pre-modern human civilization would entail very limited variation in cultural environments, so sanity may be reasonably expected to be universal in our ancient and recents past, certain anomalies and idiosyncracies not withstanding, however; modern civilization entails such a degree of economic specialization, that a civilization norm for sanity may not be possible due to diversity of environments.
5. Taken to a futurist extreme, it is plausible that interdependent economic sub-cultures may develop within a civilization, each with various psychological norms for sanity.
6. The social movement in modern society generally called “progressive” appears blind to the apparent dichotomy required to promote a diverse society that simultaneously maintains a unified psychological norm.
7. It may be worthwhile for us – modern civilization – to explore what makes any particular psychology more or less adaptive, and shift focus awat from “correcting” psychologies that diverge from established norm.