Do Bald Men get all the Girls?
This is science, not science fiction. Research has shown that bald males command a larger harem of females than their hairier counterparts...that is, if the bald male is a maneless Tsavo lion from Kenya...
In humans, male pattern baldness (or androgenic alopecia) has been linked to a number of biological pathways. I will only focus on the best publicised cause, an over-responsiveness to DHT, or dihydrotestosterone for those who enjoy long words. This hypersensitivity may be due to a number of factors. For instance, high levels of the receptor for DHT on hair follicles, or a characteristic and more sensitive structure of the receptor in predisposed people, can cause the hair follicle to detect more DHT than is good for it. In fact, one proposal for why hair is lost in a particular pattern (hence the term male pattern baldness) is because hair follicles in the regions of typical hair loss normally express higher levels of the receptor. Chief among the culprits though, at least according to current thought, is an overproduction of DHT. The enzyme 5-alpha reductase converts testosterone into DHT. In people predisposed to baldness, the levels of this enzyme is often raised in the scalp and skin, resulting in a higher concentration of DHT that can attach to the receptors on hair follicles.
On the flip side, if you have average levels of 5-alpha reductase but high levels of testosterone, it may also be possible to get more than a healthy balance of DHT, but this hypothesis is somewhat more controversial. But in support of this idea, although the pattern tends to look slightly different, women can also exhibit male pattern baldness. Normally, oestrogen counteracts the effects of testosterone, but after menopause a woman's oestrogen level falls and her testosterone (yes, women produce this 'male' hormone too) can now be turned into DHT and cause hair loss.
DHT is thought to promote hair loss in three ways: 1) Healthy follicles grow hair for a time, usually for 2-5 years, and then take a break before starting to grow hair again. DHT shortens the hair growth time and increases the follicle's hair growth holiday. This results in fewer new hairs and shorter ones at that. 2) Immediately before a healthy follicle stops hair growth, it shrinks and the hair it produces is thin and weak (vellus hair). DHT causes the follicle to shrink prematurely which is why bald people have peach fuzz on their heads. 3) Follicles need a blood supply to be nourished. DHT may cause less blood to flow to the follicles.
Bald lions So where do the Tsavo lions come in? Unlike balding men, Tsavo lions do not lose their pre-existing hair - their manes just never grow. Nonetheless, it has been suggested that they are subject to something akin to male-pattern baldness because their manelessness may be caused by elevated levels of testosterone. This is only a hypothesis; the field work testing hormone levels of these lions has just been started a few months ago. However, maneless Tsavo lions have a reputation for being extremely aggressive, a trait linked to high testosterone. If they do have more testosterone than the average African lion it seems reasonable to suggest that more of this hormone is turned into DHT, which stops their manes from growing due to the three biological actions listed above.
It is important to remember though that this may not be the cause of their baldness. Even if their testosterone levels are high, there may be other more important genetic reasons for their lack of manes. Male Tsavo lions live in two types of social groupings: Adults roam as the sole male among a very large number of females in a group called a 'pride'. This is an unusual social structure for lions since there are usually at least two males in every pride. Another bizarre social feature of these lions is that nomadic males stick together. This is very thought-provoking, particularly when it is realised that males in a pride actively do not allow other males to join. Why would some lions not tolerate other males while others seek their companionship? The idea is that these are coalitions of adolescent males that hunt together, but once their testosterone levels peak, they become too competitive and the group splits up.
Bald and a social outcast, or a sex magnet ? Whether or not the attitude could be proven accurate statistically, there is a common conception out there that human females find bald men less attractive. Adult Tsavo lions don't seem to have that problem though. Not only does one guy get ALL the girls, but he gets more girls than the other African lions with hair would even if they were the only male in their pride. So, is this social construct a female choice or a male choice? Do the females choose to cluster around the bald male, truly making the group a 'male pride' or is the bald male forced to live only among females because there would be too much competition amongst other adult males? Unless we learn to speak Lion Lingo and question the lions directly, I suppose we will never know the answer to that question with absolute certainty. I am no zoologist, so it is possible that testosterone levels have nothing to do with social groupings, or manelessness, among Tsavo lions and it is just a peculiarity of this group.
But what if the social grouping of bald animals did have something to do with testosterone...perhaps if it we looked into it more closely, we would find something similar in humans. Perhaps men whose hair loss stems from other non-hormonal causes really ARE less attractive to women because, well, females like hair. In essence, nothing more than cosmetic squeamishness. And perhaps men whose hair loss is hormonal are MORE successful with the ladies because they send out invisible signals (pheromones) responsible for chemical attraction. Or perhaps they don't get along well with other males with clashing hormonal profiles and have had to learn to understand women better instead. Naturally, this is all speculation on my part, but it makes you wonder what lions from some remote part of the world could potentially teach us about ourselves and our dispositions!