Why Is Prince William Going Bald?
Prince William in 2007.
Credit: Alexandre Goulet

In the days leading up to his wedding day, the spotlight has been on Prince William. Glinting in that light is a spot a bald one. Why is the otherwise handsome 28-year-old already losing his hair?

The simple answer is that androgenetic alopecia, or male pattern baldness, runs in William's family. His father is balding, his paternal grandfather is bald, and his maternal grandfather was bald: with such a genetic predisposition, poor William's hair may have been doomed from the start.

Several genetic defects have been tied to premature hair loss, and scientists suspect there is interplay between them. One highly influential gene appears on the X chromosome . Because men have only one X chromosome which they inherit from their mothers, the fate of their hair can be strongly affected by baldness passed down by maternal ancestors. But bald fathers can have a strong influence, too in fact, men with bald fathers are between five and six times likelier to go bald than men with non-bald fathers. However, there is no scientific consensus about which paternally inherited gene influences hair loss.

The X-chromosome gene linked with balding controls androgen, or male sex hormone , receptors. As men age, their increasing androgen level constricts the hair follicles on their heads, resulting in hair thinning and loss in a characteristic though scientifically unexplained pattern. Most Caucasian men go bald eventually: 50 percent to 60 percent start losing their hair by the age of 70. But a defect in the androgen receptor gene is what causes premature balding like William's.

A deeper question is why baldness evolved and spread in the first place.

Studies show bald men are perceived as being older and wiser than their hairy compatriots, leading some evolutionary psychologists to hypothesize that hair loss is a sexual selection tool: Women follow the visual cue as they select a mate to distinguish experienced men from boys.

In today's world, it seems counterintuitive that baldness would give men a sexual advantage. The book "Hair Growth and Disorders" (Springer, 2008) explained that "Current societal attitudes towards male pattern balding vary between indifference and negativity. An example of the latter is the reported high frequency of an apparent full head of hair amongst members of the American House of Representatives."

But evolution cooks up traits very slowly certainly slower than shifts in societal fashion and male pattern baldness may be a genetic remnant of an evolutionary advantage of the distant past. "Whereas balding is now seen as a feature of aging and declining vigor, it may have had quite different implications in our evolutionary ancestors , where only young men counted and amongst whom balding would have been relatively uncommon," Ulrike Blume-Peytavi, one of the book's editors, wrote.

Amongst young men competing for mates, a rare balding youngster like Prince William may have benefited by seeming older, wiser and more sexually mature. (It may be more than coincidence, then, that the aptly named Prince Harry, William's younger brother, has both a full head of hair and a reputation for being less mature and wise than his sibling.)

Baldness may have survived to the present day by linking itself to increased androgen production. Bald men have higher levels of androgens particularly a potent one called dihydrotestosterone than men with full heads of hair. "Whether this translates into greater reproductive success is unknown and difficult to verify," Blume-Peytavi wrote, "but it is perhaps the most likely explanation for the survival of balding genes into modern man."

Follow Natalie Wolchover on Twitter @nattyover.