These is a tremendous incentive to be an ant if you live in a climate with a real winter where you have to rely on food you have put away and you have to have a heating source stored up (firewood)
The peoples and tribes who failed this test died off
If you live in a more moderate climate without these challenges the brain doesn't need to develop so much and you can have a "live for today" attitude. No need to plan for the future when you have no winter. Dry seasons can be a challenge to survival that you have to plan for and so can living in the desert. You can find both in the tropics and other places with no winter
I've often suspected that cold is the mother of western civilization and maybe higher IQ's too.