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One of the theories on why our ancestors from Africa developed intelligence is due to dramatic and periodic massive climate change. I think it’s every two hundred thousand years, the Strait of Gibraltar slams shut. The Sahara turns into a green forest. Then, the strait opens, and the Sahara becomes an unlivable desert. (Another possible culprit is what is today Central America closing up North and South America, or possibly a combination.)

Living up in the trees became impossible as for much of Africa they vanished over a generation or three. These multiple transitions would affect things like the amount of body hair and how tall and upright our ancestors would become. Taller to see over the grass and upright walkers for the same reason. Those who became more intelligent, which was required in a more dangerous ground dwelling lifestyle, well, those people reproduced, and their traits carried on and improved us all.

My point is even “catastrophic” climate change would simply be something we adjust to. It’s not like we can stop things that cause these types of events. (It’s the Sun, stupid!) The analysis I’ve seen says we could spend every cent the entire world makes, and it wouldn’t affect the temperature by just one degree. So, live for today and we’ll adjust when and if we have to.

Agree. And we have made adjustments. Just looking at the smaller warming and cooling cycles (meaning not millions of years, but the centuries long cooling drops followed by centuries long warming periods) allows us to stay withing the timeframe that different people groups have had written languages. In other words, we can tell from history (which technically means written) what adjustments were made.

Below are some adjustments people/culture have made that I can think of off the top of my head.

1. During the Little Ice Age (roughly AD 1300 to mid 1800's) Europe adjusted from a mostly grain diet because the grain couldn't handle long droughts followed by damaging rains (life during the warm periods is great, it's the cooling periods that suck). So after Spain took over Peru, the conquistadors brought back to Europe the potato plant and, it could be argued, the potato saved Europe.

2. During the cooling periods cities tend to depopulate in part because a relatively small area of land has too low crop yield to feed them. So they spread out. Bible note: I believe only one famine in the Old Testament occurred during the Era of Judges, which began roughly at the bottom of the small blue dip left of the 3 mark in the graph below (over 3,000 years ago) and temps rose until about 11th century BC at the top of the small red bump to the right of that. The same 11th century that the prophet Samuel anointed Saul. Thus, the Minoan Warming Period corresponds to the Era of Judges, followed by the Era of Kings during the Greek Dark Age Cooling Period.

3. Anglo-Saxons were kicked out of the homeland in Germania during the Dark Age Cooling Period (roughly AD 300 - 900) by the Germanic Goth tribes. The Goths had been kicked out of their homeland from the Huns (forcing the Goths into what was left of the western Roman Empire and destroying it, then pushing them further into Germania and forcing out my Anglo Saxon ancestors). Some say that the Huns did this because climate change (the cooling version) lowered their crop yields and forced them to take over other folks land. Likewise when my Anglo ancestors were forced to Denmark they didn't stay there long. Some say the main reason they took over Britannia was because the land was too marshy and was too hard to grow crops during the Dark Age cooling period.

In Europe, when the second to last glacier (Riss) melted about 150,000 years ago, there was a long (~20,000 years) interglacial (Riss-Wurm), which was actually quite warmer than the present time interglacial (Wurm-???).
Humans took advantage of it, and spread North, all the way to Scandinavia.
Then the Wurm glacier hit and people disappeared not only from glaciated area, but even from the no glaciated Central Europe, which turned into cold tundra, not suitable for life of primitive people of that time.
People survived (barely) the Wurm epoch only at the southmost (Spain, Italy, Greece) Europe.

Then, some 11,000 years ago, Wurm glacier suddenly melted and people quickly moved back North!

I am actually wondering, how will they call the next glacial? And present epoch? (Wurm-???)