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  Obviously, men have more visible body hair than women do. But who’s ahead by race and region? It depends. In 1994, biologist Valerie Ann Randall and colleagues at the University of Bradford (UK) looked at a lot of hands and found that if you rank humans according to the amount of hair on their middle finger joint, various Europeans score as hairiest: 80 percent of them have hairy fingers. Next come the Egyptians and others living in the countries at top of the African continent (52–71%), followed by the Japanese (44.6%), Mexicans in the Yucatan (20.9%), African Americans (16–28%), and Inuits (1%). The original inhabitants of the Andaman Islands, in the southeastern Bay of Bengal, score absolute zero—not a hair to be found on a single knuckle.5 As for full body hairiness, the clear winners are the Ainu, the Australian Aborigines, the Toda of the southern Indian subcontinent, and their Davidian compatriots up north. As a rule, Caucasians have more body hair than Africans and Asians. Brunettes, such as the southern Italians, have more body hair than blondes do. The least hairy among us are Native Americans, Africans, the East Asians including but not limited to the Burmese, Chinese, Japanese, Koreans, and Vietnamese—and blonde Caucasians.

  Every hair on the human body begins to grow while we are still in the womb. By the time a fetus is slightly more than five months old, all his follicles, the pits in the skin from which hair and feathers grow, are sprouting lanugo, fine downy hair that covers his body from head to toe and provides some insulation for the developing individual with virtually no body fat. Some babies, especially those born prematurely, arrive with a little lanugo still visible, but most of us lose it by the time we emerge into the world.6 All the follicles an individual will ever have form while the person or animal or chick is in the womb or egg. With hair, the shape of the follicle determines the shape of the strand. Straight follicles send out straight hair; curly follicles, curly hair, and no curling iron or straightening wand will change this basic design that may (or may not) be visible on the newborn infant’s head.

  Once born, we develop two clearly defined types of body hair that arrive at clearly defined stages of life on clearly defined areas of our bodies. The first is vellus hair, from the Latin word villutus meaning velvet. This hair is thinner than lanugo, so short and fine that if you didn’t know it was there you might not know it was there. Vellus hair appears during childhood on every inch of the body except the lips, palms, soles, back of the ear, and the belly button. It’s still there in adulthood, still fine, still hard to see, but if you are counting strands one at a time, vellus hair is what allows anthropologists to say that we indeed have as much hair on our bodies as do our chimp cousins. The second kind of hair is androgenic hair, a form of hair that develops at puberty, stimulated by rising levels of the male sex hormones androgens (both men and woman have androgenic hormones, although men clearly have more than women do). Androgenic hair is similar to the hair on your head but has a shorter anogen (growth) period and a longer telogen (resting) period, the time before it falls out to be replaced by the next hair growing out of the follicle.

  Unlike scales, the hardened folds of the topmost layer of skin that cover a fish or a snake or a lizard, hair, pelage (fur), and plumage (feathers) are extra added attractions. All three are soft, protein-based structures that cover and protect the skin. All may be deployed in a protective manner. And all are both decorative and play a role in both emotional and sexual display.

  Hair and feathers are similar but not identical in design. Both have three layers: the cuticle, the cortex, and a hollow tube. The cuticle is made of flat, overlapping cells of keratin, the “dead” protein also found in finger- and toenails, hoofs, and claws. The cortex underneath is packed with keratinized cells plus pigments that lend hair or feathers their color. Inside the hair shaft (or the center “rod” of the feather) is a hollow space filled with cells packed close together. The one important difference between hair and feathers is that while when feathers emerge from their follicles alive, except for the bulb at the end that, as every television detective show teaches us, contains our unique identifying DNA, hair is dead on arrival.

  HAIR & FUR & FEATHERS

  What they look like

  Human hair: The diameter of a single strand varies from 30 ug to 80 ug (ug = microgram = 1/1000 of a milligram). The hairs on your head are smooth, and all will grow the same length. The hairs on your body are coarse, and how long they grow depends on where they are.

  Animal fur: The diameter of a single hair on an animal’s body ranges from 25 ug for a strand in a dog’s fur to 180 ug for a cow, which does not have fur but does have single hairs. Human hair grows in a single layer; animal fur has two layers of hair, a coarse top coat and a smooth, sometimes fuzzy undercoat next to the skin.

  Feathers: Like fur, feathers are layered with vaned feathers on top covering the entire body and softer down feathers underneath, next to the skin. The quill (the bottom tip of the feather) is the end of a hollow tube called a rachis that runs up the length of the vaned feather. Soft, feathery-looking strips called barbs branch off the rachis, and small barbules branch off the barbs. Tiny hooks called barbicels enable the barbs and barbules to link up, forming a more or less solid and protective surface. (As they break out of the egg, some baby birds are covered with down analogous to human lanugo hair; as the actual feathers grow, they push out the down.)

  How they grow

  Human hair: Each hair grows independent of its fellows, and unless you cut it, it will continue to grow from now until maybe forever. Or at least as long as you live. According to Guinness World Records, the “longest beard so far” is the one that decorated the chin of Norwegian-born Hans N. Langseth. The beard measured 17 feet 6 inches at the time of his burial in 1927 at Kensett, Iowa, the town to which he had emigrated fifteen years previously. It now resides in the Smithsonian Institution, to which it was donated by members of his family in 1967.7

  Animal fur: Animals from house cats to horses to polar bears enhance or shed some of their coats at different times of year either to build a warmer one in winter or to cut back to a lighter one in summer. Some animals, such as arctic foxes, may also change color from brownish to white to fade into the background and protect themselves from predators in winter snow. The shedding/replacing process is believed to be triggered by changes in both temperature and the amount of daily sunlight, and there are at least two studies that suggest a similar change affecting how fast and the length to which human hair grows.8, 9

  Feathers: Like animal hair, feathers have a more or less defined life cycle; each worn out one is replaced with a new one. Like cats and dogs and other animals that shed, many birds periodically molt, again, to make their “coats” heavier or lighter.

  How they protect the body

  Human hair: Humans may lose as much as 50 percent of their body heat through an unprotected head. Absent a hat, hair on a human head reduces this heat loss and along with hair in a beard and/or mustache offers some protection against sunburn. Hair in the nostrils and perhaps most visibly in the male ears protects by keeping out flying insects and floating debris.

  Animal fur: The hair in animal fur protects against both heat and cold. It is also water resistant, a kind of natural raincoat that enables animals to dry off simply by shaking, a phenomenon well known to every dog person. When the fur is standing erect, it provides a shield that keeps a layer of warm air next to the animal’s skin. (Not even very hairy humans have enough hair to do this.)

  Feathers: Like the hair on many animals, a bird’s feathers are relatively water resistant, and when erect, like an animal’s fur, the feathers ward off the chill by holding a layer of warm air next to the body.10, 11

  HOW WE LOST OUR HAIR

  While we still have body hair, it is not as visible as it once was, so we are apparently (but not really) hairless. No one knows for sure exactly how we came to be “naked apes,” but there are many possibilities, each with its own arguments, pro and con. A read-through of the literature suggests a reasonable five: water, temperature,
clothing, parasites, and sex.

  Water babies. In 1960, marine biologist Alister Clavering Hardy (1896–1985) presented his “Aquatic Ape Theory” to an audience at the British Sub Aqua-Club. Hardy’s thesis was that some of our earliest ancestors had once lived in and were surrounded by water.12 The argument was actually meant to explain our bipedalism (standing up on two legs) because had we remained crouched over on four, we would have drowned. But others use it to justify our absence of visible body hair, saying that smooth bodies made is easier for us to hunt for food in water. A second water-based theory is that the loss of body hair allowed us to tolerate higher environmental temperatures and thus reduced our requirements for drinking water.13 Finally, because fur slows swimmers down but does not keep them warm, the third water-related theory is that like whales and walruses and other aquatic mammals, we lost our fur and gained a layer of a more effective insulator, body fat.14 The counterargument to all three possibilities is that even if we lived in and around water, we’d have to come back on dry land to sleep and would need our body hair to stay warm at night.15

  Hot stuff. Many mammals stay cool by circulating their blood through the carotid rete, a network of blood vessels that cools the blood as it travels up to and down from the brain. Humans do not have an effective form of this cooling system, so when our ancestors came out of the relatively cool forest onto the very warm African savannah, the first thing they noticed might well have been how difficult it is to cool down a fur-covered body. Our response? Evolve to a relatively naked body with a stepped-up number of sweat glands. All mammals have sweat glands, but ours are much more effective than most. For example, your dog has sweat glands but only on his feet, so he has to pant to cool down, but like other primates and horses, humans have sweat glands that open onto the surface of the skin to secrete clear, salty liquid that cools the body. The counterargument is the same as for the Aquatic Ape theory, i.e., naked bodies have a hard time staying warm in the cool at night.16

  Shirts and skirts. This theory, known in some circles as the vestiary hypothesis (from the Latin vestis meaning clothes), suggests that as our brain became big enough to reason, we discovered that we could solve the night chill problem by inventing clothes, and after that a natural preference for smooth bodies produced a natural selection that continued to perpetrate relative hairlessness. The counterargument is that the most protective clothing appeared in places where humans already had natural protection in the form of the most body hair.17 The counterargument is that, yes, they had insulating hair, but the hairiest people, such as the Ainu, lived in places like northern Hokkaido and the Kiril Islands, where it was really really cold, so naturally they required more thermal protection than human fur might offer. And some suggest that hairy people didn’t need clothing to protect against the ordinary elements—sunlight, rain, wind—while hairless people did.18 Seems a bit circular, doesn’t it?

  Beating the Bugs. Evolutionary biologist Mark David Pagel of the University of Reading (UK) says out loud what every mother of a young child knows: insects such as lice love to nestle into fur and hair. When they do, they bring along many unpleasant possibilities such as West Nile and Lyme disease, not to mention intractable itching. Losing our body hair reduced the incidence of infestation, making smooth hairless skin more sexually attractive, thus increasing the number and dominance of naked apes.19

  If exactly how we came to look mostly smooth remains a mystery, where we have hair and how we use it is plain as day on three distinct sections of our beings: The top, the middle, and the bottom.

  Human Body Hair

  HAIR ON TOP

  Once we stood up on two feet, the skin on our scalp was more exposed to the radiation in direct sunlight, and the brain to its heat because, as noted, we do not have an effective carotid rete with which to cool blood circulating through the brain on its way back down to the rest of the body. Thanks to evolution, the skin on your evolved head is not as sunburned or as warm as it might have been without the thick mop that reduces the risk of scalp cancer and keeps your brain ever so slightly more protected than it might otherwise have been.

  Three or four inches down, the hair above your eyes—your eyebrows—catches drops of perspiration tricking from the forehead before they can splash into your eyes. A few millimeters lower, your eyelashes bat away airborne dust and dirt before they can float onto your sensitive eyeball. And the small moving hairs inside your nostrils sweep detritus away from there, as well. Hairy ears are so prominently male that it once seemed the gene for the trait might actually live on the Y (male) chromosome. It didn’t.20, 21 But unlike follicles on top of the aging male head that become less sensitive to androgens as we grow older, producing less and skinnier hair, those in the aging male nose and ear become more sensitive, enlarging to produce longer, bushier hair.22 Like the hair on the head, the beard on the male chin reduces the amount of solar radiation hitting the face, once again lowering the risk of skin cancer while at the same time hinting at a larger, more masculine chin and jawline underneath, a trait many women find sexually attractive.

  This is a good thing because arguably the most important role for body hair, beginning with the hair on the head, is its value in helping to ensure the continuation of the species. Bald may be beautiful, but a full head of male and female hair is always attractive even if it’s not totally natural: For example, according to a quintet of John Hopkins scientists, men who get hair transplants are perceived as being younger and more attractive.23 Male facial hair is also attractive, from time to time, according to the fashion of the day. Evolutionary biologist Robert Brooks of the University of New South Wales (Australia) has carved out a niche for himself as a man who studies “the evolutionary consequences of sex [including] the evolution of mate choice, the costs of being attractive, sexual conflict, the reason animals age and the links between sex, diet, obesity and death [as well as] the evolutionary and ecological consequences of sexual reproduction.”24 In 2014, he and his colleagues used their Facebook site, “The Sex Lab,” to recruit female volunteers for a study designed to demonstrate that the female preference for male facial hair follows a rule Brooks calls “negative frequency-dependent sexual selection.” Translation: the less common a trait, the more attractive it seems. When fewer men have beards, more women prefer men with beards. In Brooks’s study, nearly 1,500 women (and about 200 men) applied to rate the attractiveness of different samples of men’s faces with “four standard levels of beardedness”—clean-shaven, light stubble, heavy stubble, and full beard. One group was shown pictures of men with full beards, a second group, clean shaven men, and a third group got an even mix of all four possibilities, from full beard to no beard. In the end, Brooks says, both women and men favored the heavy stubble and full beards more when they were rare, less when they were common, and did the same for clean-shaves. “We know beards go through cyclical fashions,” Brooks says. “There is a wonderful paper studying photographs of men from 1871 to 1972 in the Illustrated London News. Sideburns moved on to moustaches, then full beards. In the 1970s it was handlebar moustaches. In the 80s it was Magnum PI moustaches. In the 90s we saw a lot of clean shaven men, and now big bushy beards are back.” The last, he suggests, may have been due to the financial upset of 2008 when men attempted to increase their chances of getting a new job by “turning up their masculinity” with facial hair.25

  It often works because real science suggests that beards advertise health, maturity, and power.

  First, like other body hair, beards may be host to a variety of bugs. Wearing one seems to say: “My immune system can beat any bug in this town.” Second, boys don’t have beards. Men do. In 2012, when Australian ecologist Barnaby Dixson and Canadian psychologist Paul Vasey showed men and women pictures of the same men, first bearded and then clean-shaven, both sexes said the men with beards were older. Third, the Dixson/Vasey volunteers ranked bearded men more aggressive. And on a social status scale ranging from 0 to 5, the bearded men were regularly scored as being scarier,
that is, more aggressive, than the clean-shaven ones. Further evidence of a link between beards and social status comes from a 2004 paper in the journal of Britain’s Royal Pharmaceutical Society: a survey of male academics at UK universities found that full professors were “significantly more heavily bearded than lower staff like lecturers and research fellows.”26 Until, that is, the next cycle began, at least in Britain, around 2014, when BBC personality Jeremy Paxman shaved clean, setting off, Brooks says, perhaps wryly, a momentary debate about pogonophobia (from pogon, the Greek word for beard), the fear of beards.27

  THE PRICE OF MALE FACIAL HAIR

  The average American male begins to shave when he is about 15 years old. His average life expectancy is currently 76.1 years.

  The average man’s face contains anywhere from 5,000 to 30,000 whiskers, each of which grows at a rate of about half an inch a month, 6 inches a year, or 366.6 inches (30.55 feet) from age 15 to age 76.1

  The average shave only lasts a little more than three minutes, but altogether, keeping a male face smooth between age 15 and age 76 will require about 60 hours (2.5 24-hour days a year) or 152.75 days (five full months). In comparison, over a lifetime, women spend only 1,728 hours (72 days) shaving their legs.28, 29

  HAIR IN THE MIDDLE

  At puberty, males also begin to sprout visible hair on the chest and abdomen, the latter reaching downward toward the pubic region. Male arms are hairier than female arms, with coarser hair from elbow to wrist. The same is true for human legs, with the heaviest growth at the bottom, from male knee to ankle, not to mention occasionally noticeable tufts of hair atop male toes.

  As every cat owner knows, and Darwin, a devoted dog person, wrote, “Cats, when terrified, stand at full height, and arch their backs in a well-known and ridiculous fashion. They spit, hiss, or growl. The hair over the whole body, and especially on the tail, becomes erect. In the instances observed by me the basal part of the tail was held upright, the terminal part being thrown on one side; but sometimes the tail (see fig. 15) is only a little raised, and is bent almost from the base to one side. The ears are drawn back, and the teeth exposed.”30