It was year seven and it was sex education. Our red headed teacher asked our pimply faced class if we had any questions. Question one: “Have you ever had an erection?” Giggles. Question two: “Where is the G-spot?” Giggles (with intent listening). Question three: “If you have red hair do you have red pubes?” Giggles ensue, teacher says yes, and the face of the only other red haired boy in the class promptly turns the colour of his hair. Question four: “Why are pubic hairs curly?” No giggles this time, just intent listening, but unfortunately, no satisfactory reply. Years later, I’m here to satisfy this curiosity once and for all.

Hairing out an issue
 All hair on our body grows from hair follicles. Hair follicles, look a bit like sprouting onions with the bulb deep within the skin and an opening sprout on the skin surface. The shape of the bulb controls the type of hair that will grow out of the follicle. Round bulbs that are lined up straight against the skin produce straight hair, like the fine hairs on our arms. While, oval shaped bulbs positioned at a sharp angle produce course and curly hair. Before puberty, the hair follicles around our private bits are round and on a straight angle, but during puberty this all changes.

 During puberty our body makes sex hormones called androgens. The hair follicles in the pubic regions are very sensitive to androgens, and it makes the bulbs change shape, going from round to oval. As a result, curly and thick pubic hair starts popping out. Guys get more pubic-type hair than girls, for example, on their chest, back and face, this is because they have more androgen flowing throughout their bodies.

What about the hair on our head?

The difference between curly and straight hair on our heads, has less to do with androgens and more to do with genes. This is because follicles on our heads are less sensitive to hormonal changes, but the same bulb-shaped principle applies. Curly hair grows from oval shaped follicles, and straight hair from round follicles, but the shape of the bulb and the angle of the follicles won’t usually change during puberty. So when it comes to the hair on our head, the shape of the follicle is mainly caused by genes.

 Why the hair follicles under our arms or around our genitals are overly sensitive to androgen is quite a curly question that scientists are still trying to work out. Some internet bloggers reckon that our pubic hair is short and curly so you don’t poke your eye out when you’re “working” down there. (The innovation of evolution!) But it’s more likely that, evolutionarily speaking, curly pubic hair is the best way to keep dirt away from our private parts, and to keep them warm.