Every existential problem is downstream from having dramatically more energy--carbon capture, desalination, food beyond remaining arable land and healthy soil.
Or the opposite: having dramatically less energy. Our ancestors were not destroying biodiversity, and were running on renewables :-). Our modern problems came with fossil fuels...
Our ancestors didn’t destroy biodiversity? I think the extinct mega-fauna of prehistory disagree with you. Ironically enough, their remains probably make up the gasoline in your car.
> They also killed each other for land. Sometimes they starved.
If you don't, good for you. Don't think everybody has that chance.
> As for us, we’ve already emitted too much. If we merely stop it’s still going to be a bad century.
If we stop, it's going to be complicated times. If we don't... well we will have more conflicts for land (those that remain where humans can survive) and famines.