Why did people have to learn to make clothes and build shelters?

During the Ice Age, humans would have frozen to death if they didn't take shelter in caves and made the first sewed clothes of animal skin. They had to learn to make shelters so they could keep out of the harsh climates that the Ice Age brought, and they made clothes so when they had to go out and hunt in the ice and snow, they would be warm because they knew they would freeze to death if they didn't.