>I may also mention Easter Island, but the story there is subtle, and I don’t understand it well, so I should probably refrain.

On a first account the Easter Island story doesn't sound as if there was a complete resource exploitation:
citation from "What Happened On Easter Island — A New (Even Scarier) Scenario":
>According to MacKinnon, scientists say that Easter Island skeletons from that time show "less malnutrition than people in Europe."

but it seems there was a "mass extinction" of trees, so maybe one can take the Easter Island example at least as an example for
possible scenarios of anthropogenically shaped environments.

>But they kept going on rat meat and small helpings of vegetables. They made do.
>One niggling question: If everybody was eating enough, why did the population decline? Probably, the professors say, from sexually transmitted diseases after Europeans came visiting.

Yes it seems birth control was less likely to be adapted in earlier times, so since there was no famine and since there were no predators, like wild animals, diseases are a possible option that the population didn't soar. However in some other poulations cannibalism and other forms of killings were also leading to that result. Was there any investigation into that direction?

>Humans are a very adaptable species. We've seen people grow used to slums, adjust to concentration camps, learn to live with what fate hands them

It sounds inappropriate to say that "people adjust to concentration camps". That is some people seem to adjust, but some do not adjust and expecially with respect to victims the wording is more than awkward.