"Since the dinosaurs" is doing a lot of heavy lifting here. I wasn't exclusively talking about the period after the dinosaurs as that's a rather arbitrary to limit the argument to.

Earth has experienced at least two major extinctions where most life just ceased to exist. Both times due to massive climate events.

The previous glacial period does not compare to what global warming will cause. And we've had plenty of huntable food sources back then.

Biodiversity is the one key factor that determines if Humanity will survive at all. We like to think that we don't need biodiversity to survive like every other lifeform on Earth, but it is essential to our survival.

If biodiversity goes, Earth cannot sustain any population of humans.