Adjust to new environments or go extinct
When I was 18 years old at university in Texas I realized the need to acclimate to the cold and that I was a whimpy tropical animal (I had recently moved from living many years in the Amazon region). I was watching a sports game standing on aluminum bleachers and it was only about +28F. I was wearing a heavy parka with hood and beside me was a friend from Alaska wearing only blue jeans, shoes, and a short sleeve T-shirt. He was fine, but I was shivering. So I quickly realized I needed to adjust to my new environment, which was nothing like Alaska or Canada, those places would have left me totally immobile at the time, possibly dead. Funny thing is I have been camping with people who complained about the cold and just sat there. Well!!! get up and move around "for the love of Pete". Common Sense!