Hair is made of keratin, the same substance that forms nails and the barrier at the top of the skin.
Like other parts of the skin, hair helps protect the body. Eyelashes and eyebrows shield the eyes from sun, dust, and perspiration. Nasal hair helps reduce your intake of dust and other foreign bodies. Hair on the scalp provides some insulation. However, as the human species has evolved and become more sophisticated in protecting itself from extremes of temperature, it has less need for body hair.