The reason why the pubic hair appears curly is because of its physiological function to determine. The main function of pubic hair is to keep warm, reduce friction, absorb sweat and dissipate heat, and it is distinctly different from human hair. The presence of pubic hair can ensure that the testicles are at a normal temperature, avoiding high or low temperatures, which can affect the quality of sperm. The presence of pubic hair can also cushion the painful friction that occurs during intercourse. If the pubic hair is particularly flat, it may cause some tingling or other effects on the surrounding skin. Because the pubic sweat glands are very developed, sweating more, fluffy pubic hair can play a good role in ventilation, so because of the natural evolution of human physiological function and the formation of curly pubic hair.