Humans have hair for several important functional reasons beyond aesthetics. Hair on the head protects the scalp from the sun, reducing the risk of sunburn, and helps preserve body temperature by insulating the brain, which generates a lot of heat. Additionally, hair offers some protection against minor physical impacts to the head. Hair in other parts of the body also serves practical roles such as providing warmth, protecting sensitive areas like the nose and ears from dust and particles, and augmenting the sense of touch through follicles. Hair follicles can also react to temperature changes to help regulate body warmth by standing up to trap heat or lying flat to release it. Thus, despite modern clothing and other protections, hair remains a useful biological feature for protection, temperature regulation, and sensory functions, with the hair on the scalp being especially crucial for protecting the brain and skin from environmental damage.
