You're right that the rise of humanity coincides with the last 12k/optimal temperature years. However, during the Cretaceous (approx 145-60 million years ago) when most places in the world had avg temps in the 90 d F range and were largely "tropical" with no ice, the dinosaurs thrived. It would seem that humanity's numbers will decline while moving northward (above 60th Northern parallel, about 60 d F during Cretaceous?), yet with our advanced tech…survivable? My take:

https://scottvern.medium.com/what-the-worlds-weather-and-farming-may-look-like-in-2100-9d3e30ab18bf