Setting: 50kya in the Environment of Evolutionary Adaptedness
Imagine you and your band are being chased by a group of animals 50kya in the Savanna. You look back as the herd is almost at your band, about to rip them to pieces. When, suddenly, there is a bright, blinding flash and the animals stop in their tracks, giving your band enough time to escape.
Your band looks back about 200 feet away to see a man standing there with his bald head standing at the animals, directing a beam of UV rays at the group. The women stand there, lovestruck, as this man just saved the band.
This man—and men who looked like him—were then taken on many expeditions and the same thing happened whenever the band got into trouble out in the grasslands. A group of animals threatens the band? No problem, there is a bald man there, waiting to use his head to blind the back so the band can get away.
Women then started showing more affection to the bald men as they proved they can save the band, and without having to risk harm, at that. So women started mating more with them. Bald men then gained more power in the society, as the women of course continued to pick berries while the men hunted—bald men going with both groups to give protection.
Then, over time, genes the conferred a higher chance of becoming bald became fixated in the group as it conveyed a fitness benefit from which resulted from protecting the group by shining UV rays at a pack of animals to save the group resulting in women finding it attractive and so having more children with them.
Sound ridiculous? Well, searching for claims for bald heads being an adaptation, I discovered that someone said the same exact thing:
A well-polished bald male head was often used by tribes of cavemen to blind predators. As a result every cavemen hunting group of 8 had one bald member, and thus thousands of years later 1 in 8 men experience early on set of baldness. – Taz Boonsborg, London, UK
There are other similar adaptive stories for bald heads, such as a lather surface area to receive more vitamin D:
Loss of hair creates more skin area, which means more vitamin D can be absorbed from sunlight. This would provide a survival benefit for me, which would explain this trait being passed on.
While another person makes a similar claim:
I wonder if it can be linked to the time in evolution when Europeans lived in Central Asia before moving west to Europe. Vitamin D was a scarce necessity. I like to think of my bald head as sun ray receiver. I have noticed that women 30+ are a lot more likely to be attracted to me partially due to my baldness, sometimes very much so 😉
There are, thankfully, some commenters that say it has no adaptive value. When it comes to the existence of any trait, of course, one can construct a plausible evolutionary narrative to explain the survival of the trait into the current day.
A conversation about baldness should include a conversation about bearded-ness—as I have written about before. The story goes that beards are adaptive for men, since “beards may have been valuable as a threat signal during direct male-versus-male competition for dominance and resources“, while also stating for pattern baldness that “The senescence feature of male pattern baldness may be an advertisement of social maturity. Social maturity includes enhanced social status but decreased physical threat, increased approachability, and a propensity to nurture.” (Muscarella and Cunningham, 1996). They also discuss differing sexual selection theories for pattern baldness, such as “for an increase in the visual area for the intimidation display of reddening color during anger.” So to these authors, baldness signifies social status, and if one is bald or balding, they can then show their emotions more—especially if light-skinned. So baldness is a signal of senescence—biological aging.
Kabai (2008) hypothesizes (storytells) that androgenic alopecia—male pattern baldness (MPB)—is an adaptation. Each hair follicle has its own resistance to whether or not it will fall out. So, to Kabai (2008: 1039), MPB “evolved to elevate UV absorbance and thus to provide some protection against prostate cancer.” This is a classic just-so story. I have written a ton about the relationship between testosterone, prostate cancer (PCa), and vitamin D. Blacks have lower levels of vitamin D, and higher levels of prostate cancer. (It should be notes that Setty et al (1970) showed that MPB is four times less likely in blacks compared to whites.) So, in whites, baldness was adaptive in order to acquire more UV rays.
Unfortunately for Kabai (2008), the underlying logic of his hypothesis (that the more bald a head, the higher the vitamin D production) was tested. Bolland et al (2008: 675) “found no evidence to support the hypothesis that the degree of baldness in influences serum 25-OHD levels.” This could be, as the authors note, due to the fact that vitamin D is not produced in the scalp or that vitamin D is produced in the scalp but getting sunburned would modify a man’s behavior to spend less time in the sun and so, the so-called benefits of a bald head for vitamin D production would be limited. Bolland et al (2008) end up concluding that:
there is no accepted evolutionary explanation for the almost universal prevalence of hair loss in older men. We suggest that other hypotheses are required to determine why older men go bald and whether baldness serves any physiological purpose.
Why must baldness “serve a physiological purpose”? I like how the proposal of these hypotheses doesn’t consider the fact that hair just falls out at a certain rate in certain individuals with no evolutionary purpose behind it. Everything must have an adaptive purpose, it seems, and so, one creates these fantastic stories. It’s just like Rudyard Kipling’s stories, actually.
Lastly, Yanez (2004) proposes a cultural hypothesis for MPB. Yanez (2004: 982) states that the cause of MPB is “the detention in the sebum flow moving towards the root of hair.” Those who are more likely to suffer from baldness are those with thin hair who constantly cut their hair short, or hair that is straight or low-density. On the other hand, those with high hair density and thicker hair are less likely to go bald, even if they keep short hair. This, to Yanez (2004), the catalyst of balding is cultural but, of course, is driven by physiological factors (blocking the flow of sebum to the hair follicle).
Many kinds of stories have been crafted in order to explain how and why humans—mostly men—are bald. Though, this just speaks to the problem with adaptationist hypotheses—notice bald heads; bald heads are still around (obviously, since we are observing it); since we notice bald heads because they are still around then there must have been an evolutionary advantage for bald heads; *advantages noted above*; therefore baldness is an adaptation. This reasoning, though, is faulty—it’s a kind of rampant adaptationism, that if a trait exists today then it must, therefore, procure an advantage in an evolutionary context which was then therefore selected-for.
Of course, we can not—and should not—discard the hypothesis that bald men still exist because they could direct UV rays at oncoming predators trying to kill the band, the women seeing it, and it, therefore, becoming an attractive signal that the man can protect the family by directing UV rays at other men and animals. That’s a good hypothesis that’s worth investigating. (Sarcasm.)