Hairlessness is attractive

Maybe you should add "lack of parasites" to your list of what you are looking for in a partner. A new study has found that humans evolved into their relatively hairless state to reduce the risk of parasites and flies living in their fur and to enhance their sexual attractiveness.

Many theories have been put forward as to why humans are one of the few mammals that lack a dense layer of protective fur or hair. The most widely accepted of all these theories is one which claims that humans became hairless to allow for better temperature control in varied climates. This traditional view says that fur was no longer necessary because humans learnt how to regulate the temperature in their immediate environment with the use of fire, shelter and clothing.

But researchers from the University of Reading in England published an alternative explanation in the June 9 issue of Biology Letters.

The research team under the leadership of Mark Pagel, propose that humans could effectively change their environment by producing fire, clothes and shelter. They could also lower their risk of parasitic diseases, as they could clean and change bug-infested clothes and shelters much more easily than a permanent fur coat.

Too sexy for your hair?
So why is hair distributed differently on men and women you wonder? The new hypothesis may hold an answer to this question.

"Hairlessness would have allowed humans to convincingly 'advertise' their reduced susceptibility to parasitic infection and this trait therefore became desirable in a mate," write the study authors.

Pagel's team say that the reason why women have less hair than men is due to the fact that men more commonly choose their sexual mate, so women had to be especially hairless to catch the man's eye. But, they add, the very fact that men's facial and head hair has survived throughout the centuries is proof of the continued importance of hair (or lack there of) in sexual attraction and selection.

The pubic puzzle
But what about pubic hair? Surely the warm, humid environment created by pubic hair was an ideal breeding ground for creepy crawlies? Pagel and his colleagues admit that pubic hair poses a challenge to their theory.

But they believe that pubic hair was part and parcel of the whole game of sexual attraction as is enhances the exchange of pheromonal signals. Pheromones are the scentless chemicals released by both sexes that are thought to be involved in sexual attraction.

Pagel's team suggest that future studies test their theory by investigating whether humans who evolved in the tropical areas – where there are higher rates of parasitic diseases – have less body hair than people from other regions.