Hair on the head acts as a good insulator in cold weather and a good reflector of heat in hot weather. According to Nina Jablonski, tightly curled hair is the most efficient kind “because it increases the thickness of the space between the surface of the hair and the scalp, allowing air to blow through.” A separate but no less important reason for the retention of head hair is that it has been a tool of seduction since time immemorial. Pubic and underarm
