An effective insulator is needed to maintain body temperature in an icy climate. Mammals have hair or fat that isolates their bodies, but humans lack the necessary fat and their body hair is relatively scarce, so it is necessary to protect themselves with clothing.
Mammals are characterized by two types of hair. The longest, protective, is erectile: erectile when the animal is afraid or angry, as in the neck of dogs. Underneath, the shorter hair is soft and dense, and retains air close to the skin. The air is a bad conductor of heat, so the trapped layer receives heat from the body and keeps the animal warm.
When it rains or if the animal gets into the water, the outer coat becomes tangled and forms a waterproof layer, which prevents the shorter hair and skin from getting wet and losing their insulating properties. When it stops raining or the animal comes out of the water, a simple shake removes the water retained in the body.
By taking advantage of qualities such as wool, man can imitate what mammals do. Clothing close to the skin traps the air, which is kept warm and creates a protective layer. Raincoats prevent clothes from getting wet and losing their insulating properties.
.
