There is the Astral Codex Ten Discord server (Scott is not involved) where some debates happen.
In the literature you reviewed, was there mention of late-talking as a result of trauma in early childhood/infancy occurring before speech development? If so, would you be willing to share the references? (Very late talker here, no word or babbling before the age of 4.)
"The Collapse of Complex Societies" by Joseph Tainter (1988) is a good place to start for a historical perspective. To put in relation with the Club de Rome report "Limits to Growth" (1974).