[blam]

"You have to note also that the more advanced cultures seem to be where there was the most change. They had to be smart to survive."

I agree. I think the cold taught us how to plan and have a concept of the future. Those who didn't plan when things were good(warm), didn't survive when things were bad(cold).

[U S Army EOD]

Or if things were always warm, they still survived but never learned to plan.

[Junior]

Except civilizations arose initially in two relatively benign areas along the banks of major rivers...