Hair on the head is to prevent heat loss, and to act as sexual attraction. Eyebrows prevent sweat from entering the eyes; Eyelashes prevent sweat or other foreign objects from damaging or bluring the retina.

Pubic hear, interestingly enough, serves several functions. It acts as a sort of rudimentary shock-absorber during intercourse, preventing chafing, are also to trap erotic scents (pheromones), that are often only detected subconsciously. It may also be keep the genitals warm - although sperm must be kept cooler than the average body temperature, which is why the scrotum hangs outside the body, and is not stored within.

Vile. Humans are pretty abject creatures when under scrutiny. Swiftly moving on.