> for large species such as those of the size of say humanity, it seems to have been exceptionally hostile.

That was your statement, not Wikipedia. What was that based on if not the incorrect implication about the size of mammals?

Nonetheless, I've already edited my post to make it clear that I was talking about the implications of the statement from Wikipedia.

> The pressure on mammals appears to have been consistently toward smaller size

If "the size minimum in the Coryphodon lineage occurr[ed] shortly after Paleocene-Eocene boundary" then the decrease occurred before the early Eocene, not during. The temperature actually continued to increase for several million years after the Paleocene-Eocene boundary.[1]

That pressure might have been due to the rapid changes at the Paleocene–Eocene Thermal Maximum, not temperature itself, and after the thermal maximum, size increased again even with the higher temperatures.

1: https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therm...

If there's evolutionary pressure on existing species to become smaller, and newly evolved species are smaller than those of preceding and following eras, it seems entirely reasonable to conclude it was somehow hostile for larger land mammals, no? That is not a statement that every single one was under 10kg or perfectly fit the identified trend.

We should remember that even during the adjacent times (the Paleocene and Middle Eocene) temperatures were about 8C higher than they are now, and large mammals (some of the largest ever) evolved during those times.

The decrease in size probably had more to do with the chaos wrought by whatever unknown event caused the thermal maximum than with the temperature itself.

To make this all more relevant: I'm not saying that climate change won't be disruptive. It will. I'm just saying we can adapt and endure. And I think we should plan for that, because we clearly aren't going to stop it.

It is interesting that with climate change, the public debate is mostly about 'is it man-made?' as if it'd just become a non-issue if it was. It's debating a fundamental point while we need practical solutions or even just concepts to cope with all sorts of interconnected problems on the entire spectrum of what we as humans are able to address - from microorganisms to geopolitics. While at this point, nobody is sure what will happen, societies will get a clearer picture of the imminent consequences over the next decades. At the moment, everyone seems to be waiting.