Which ethnicities are the hairiest

Hair: What We Know About Beards - And What Not

Charles Darwin was fascinated by the male facial hair. "It seems as if the beard was an ornament for our ape-like ancestors with which the males tried to charm or arouse the females," wrote the evolutionary biologist in "The Descent of Man" (1871). But he knew from reports that the growth of beards among men is very different around the world. "They are often missing from the Ceylon locals," he wrote. "Beyond India, beards are disappearing, for example among the Siamese, Malays, Kalmyks, Chinese and Japanese. In contrast, the Ainos, who live on the northernmost islands of the Japanese archipelago, are the hairiest men in the world."

How did these differences come about? Darwin speculated that they must be the consequence of sexual selection. Women in different parts of the world have had to find beards differently attractive. This was the only way to develop different beard thicknesses over many generations. It was only 80 years later that it became clear that hormones control beard growth. In 1949, Washington University Medical Center gerontologist Margaret Chieffi reported that men had more beards when they were injected with the sex hormone testosterone. But it soon became clear that testosterone alone did not make a beard.

This article is included in Spectrum - The Week, 51/2017

Interaction between hormones and genes

James B. Hamilton's twin studies in 1958 suggested that genes must play a major role in the cells of the skin on the face. For his experiments, the anatomist from the State University of New York compared (white) twins and pairs of brothers from the USA and Japanese. He shaved all the men, waited 24 hours, shaved them again, and then weighed the stubble. The result: As expected, the Japanese had a much weaker beard than the Americans. In both cultures, however, identical twins had almost identical beard growth, both in terms of quantity, density and distribution of the whiskers. In contrast, these beard characteristics were much more variable among non-identical twins and pairs of brothers.

From these observations, Hamilton concluded "that genetic factors have a much stronger influence" on beard growth "than the concentration of male sex hormones in the blood". Because differences in testosterone concentration between men of different cultures were not known. Hamilton was right. In the course of the 1970s it became apparent that it was not testosterone itself that stimulated the hair follicles of the facial skin to drive out whiskers, but the metabolic product dihydro-testosterone. In the facial skin of men with a full beard, the available testosterone is simply converted into dihydro-testosterone in large quantities.

How much beard a man wears compared to others does not say anything about how much testosterone he has in his blood. As Margaret Chieffi's experiments showed, testosterone can stimulate beard growth in the same man. An anonymous researcher therefore proposed in 1970 that the beard could grow stronger in sexually starved men. In a letter to the journal "Nature" he wrote: "During the past two years I have had to spend several weeks in an isolated location on a remote island. Under these conditions I noticed that my beard was growing down. But the day before I left the island It gained weight again, at unusually high rates. Fascinated by these first observations, I conducted a more detailed study on myself and came to the conclusion that increased beard growth is related to the resumption of sexual activity. "

Beards make an impression

"Unfortunately, no one has repeated the experiment on a large scale," says Barnaby Dixson of the School of Psychology at the University of Queensland in Brisbane. The evolutionary psychologist is one of the pioneers in beard research today. An unexpected indication of the beard's function was provided by a study that Dixson and his colleague Paul Vasey from the University of Lethbridge (Canada) published in the journal "Behavioral Ecology" in 2012. For the study, the researchers photographed ten New Zealanders and nine Samoans, each with a full beard and freshly shaved, each with three different facial expressions: smiling, neutral and aggressive. Then they had 129 white women from New Zealand and 100 Aboriginal women from Samoa rate the attractiveness of the smiling men. The women agreed that freshly shaved men were consistently more attractive to them. It is therefore clear that women do not generally find beards more attractive in cultures with strong beards, as Darwin had assumed.

But how did beards survive in these cultures? An answer was suggested in the second part of the study. In it, Dixson and Vasey showed 111 men from New Zealand and 119 Samoans the pictures with the aggressive-looking men. Again, the representatives of both cultures were in agreement: "The faces were consistently felt to be more aggressive if they had a beard," says Dixson; a result that was replicated in later studies with other cultures and with women as viewers. "One thing is certain: men with a beard are rated as more aggressive, masculine and dominant," says Dixson.