positioning in any material way to account for ice ages.

There is a ton of evidence that deforestation has contributed massively to the decline and collapse of civilizations over time. See "Collapse" by Jared Diamond. He cited the example of ancient peoples in N America, particularly in what is now the Southwestern US (the Ansazi) and the Mayans. Deforestation leading to climate change leading to population collapse was a common theme. Not just in N America.

That's at least an identifiable variable, unlike the earth's relationship with the sun, in researching why civilizations collapse or experience precipitous population declines.

Best example he cites - Hispaniola. Haiti on one side, DR on the other. The DR is a third world country, no question, but it is lightyears ahead of Haiti, which is the poorest country in this hemisphere. What's the difference? Arguably the only one that matters: the DR stopped the deforestation of its side of the island. Haiti did not.

"Collapse" is an interesting read, and is a great read for climate change skeptics (I was once a card carrying one, and still have my skepticism about predictions) who are willing to have their beliefs challenged.