Dear Big Scary Man with a Piece of Cheese,

Apparently, your friends have stumbled upon one of the eternal mysteries of the human body. There are a number of theories on why pubic hair exists, but no definitive answer. However, most sources agree that pubic hair relates to pheromones — scents that the body produces that can be sexually stimulating to others.

Believe it or not, humans have the same number of hair follicles as apes, except our body hair is generally very fine or barely visible in comparison. Yet pubic and underarm hair tends to be more visible and coarse. It is believed that the tufts of hair around the genitals, as well as under the arms, release pheromones, which may act as erotic aids.

Pheromones get trapped in the pubic 'do when apocrine glands release an odorless secretion on the surface of the skin that combines with bacteria decomposed by the secretions of the sebaceous glands. The resulting scent is different for individuals due to a genetic complex called the Major Histocompatability Complex (MHC). Studies suggest that women are attracted to men with very different MHCs than their own, perhaps because genetically diverse offspring may be more able to fight off disease. For some people, scents from these areas are noticeable and consciously increase sexual arousal. For others, pheromones might not be obvious but may be detected subconsciously.

There are other hypotheses about why we have hair on our pubic places. Some people believe that it keeps our genitals warm. In prehistoric times, when only a loincloth was worn to cover the penis or vulva, this might have held true. However, if the primary job of pubic hair was to keep the genitals warm, males would probably have hair on the shaft of their penis and more hair on the scrotum to insulate the testicles. Additionally, females would have hair on the skin of their lower torso to insulate the internal reproductive organs.

An additional theory suggests that the purpose of pubic tresses for women is similar to that of cilia in the nose (a.k.a., nose hair) and eyelashes. In this case, the pubic hair prevents dirt and particles from entering the vagina. However, one problem with this theory is that men don't have similar protective locks around the opening of their urethra.

Evolutionary scientists suggest that humans may have evolved to have less pubic hair to appeal to the opposite sex, a form of sexual selection. Skin that is clear and smooth may have come to signify health.

As far as non-functional use goes, pubic hair can be decorative or attractive to their owners or to others. It may be cut or styled in ways to appeal to sexual partners, which may increase sexual potential, at least in theory. Different cultures may have preferred norms for pubic hair, ranging from completely removed, to styled, to natural. Some of the related Q&As below explore the many aesthetic possibilities of pubic hairdos.

As with any unsolved mystery, there are probably other theories out there regarding the purpose of pubic hair, so don't be too hard on your friends if they can't answer your question!

Alice!