The Well-Dressed Ape

A Natural History of Ourselves

Hannah Holmes

• Publisher: Atlantic Books
• Year: 2009
• ISBN:
  9781848874336
• Topic: Sciences biologiques
• Subtopic: Science générale

The 'Well-Dressed Ape', aka Homo sapiens, is a strange mammal. It mates remarkably often and with unprecedented affection. With comparable enthusiasm, it will eat to the point of undermining its own health - unlike any other animal in the wild. The human marks its territory with doors, fences and garden gnomes, yet if it becomes too isolated it becomes depressed. It thinks of itself as complex, intelligent, and in every way both different from and superior to other animals - but is it, really?

In this riveting and revealing field guide to the human animal, Hannah Holmes surveys the evidence. She shows that monogamy is mostly overrated: female birds that cheat on their partners have bigger brains, and female chimps go out on the equivalent of Girls' Nights Out; that while humans can contact each other using complex lumps of plastic, spiders can send each other messages by plucking web strings, and some fish communicate by clicking their teeth, or strumming body parts; and that most animals lie - the baby baboon is notoriously devious, and 'cries wolf' to avoid its mother's wrath.

The Well-Dressed Ape is an entirely engrossing and eye-opening study of that oddest and yet most engaging of primates: ourselves. It will change the way you look at yourself - and other animals - forever.

1

QUICK AS A CRICKET:
PHYSICAL DESCRIPTION

Homo sapiens is a mammal that, uncharacteristically, travels on two legs, leaving the forelimbs free for other tasks. Although the usual gait is a walk, a rare feature in the animal’s neck permits it to run at considerable speed for astounding distances. The fur, black in most individuals, is largely restricted to the head and the junctions of limbs and trunk, although a fine pelage does cover the rest of the body. The human skin is usually some shade of brown, but can be pink in the least sunny parts of its range. Eye color is also brown in most humans, but among individuals with reduced skin pigmentation eyes may be hazel, green, or blue.

The human’s dentition is typical of an omnivore, excepting its strangely diminutive canine teeth. (In fact, this animal is surprisingly ill-equipped for physical aggression or defense.) Due to prolonged isolation of breeding populations, humans have evolved numerous morphs, or races. “Pygmies” are the smallest of these, standing less than five feet tall. Northern Europeans are the largest, with the Dutch male averaging five feet ten inches.

Sex differences are pronounced. The female carries two permanently enlarged mammary glands high on the chest. As in most mammals, the male has nipples but cannot nurse young. The sexes also differ in height, fat storage, and fur distribution. Although the human bears a resemblance to the other great apes, a careful observer will note that the human demonstrates a stronger inclination to tamper with its skin and fur, and that its excursions into trees are normally clumsy, and often injurious.

HIGHLY VARIABLE IN SIZE

In daily life I pass for a tall, blond human of the northern persuasion. In this regard I am not an ideal subject for a study of the human animal. The majority of humans have darker coloration, are physically adapted to warmer climates, and are somewhat stunted by poor diet. But the stock I have to work with is limited.

There’s me. My genes spiral back through time in a series of tall, pale primates, in a trail that goes cold in the British Isles a few centuries ago. Even the randy dentist who hopped the fence to sire my father’s mother was a tall blondie, according to the one photo that remained after he was driven from his small Maine town.

And there’s my mate, although he’s not particularly eager to shuck his clothes and undergo prolonged dissection. Besides, he’s not much different, in terms of where his DNA ripened. A strand of his emerged further south than my family’s, but not by much. His hide is a bit more olive, and his fur is darker, but he’s still decidedly European. And his offspring are a pale pair, too. We’re a northernbred bunch, although the children’s hair and eye colors do approach the norm.

But that’s us only in daily life. In the biological view, we’re perfectly human. The animal I see in my mirror is indisputably human, once you get past the blanched skin. For better or worse, I’m an acceptable specimen of Homo sapiens. And right now, the “worse” is what I’m seeing.

I close the shades and cast the clothing aside. My initial survey is disconcerting. I’m naked like a dolphin, but upright like an owl. I’m padded with fat, but have the legs of a stork. The bulb of my cranium swells over my eyes, not behind them. And I cannot deny that the animal before me has been—as though I weren’t strange enough—painting itself.

Peculiar beastie. Well, the human animal is no glittering peacock, or tyger burning bright. But by considering my anatomy one feature at a time, I expect the funny elements of my body will add up to something serious. Nature does not produce freaks just for the fun of it. There is always a method to the madness.

In the gloom I give myself a closer look. Not all humans experience anxiety about revealing their hairy parts and their assorted lumps and bumps. Lucky them. My culture has strict ideas about which parts should be revealed and how large or small those parts should be. I take these strictures to heart. Even with the shades drawn I’m nervous, standing here au naturel. This particular human isn’t at ease even on the nude beaches of California. Parts bounce. Things rub. And even when the other humans there don’t give me a second glance, their first glance is enough. Gimme garments. But this is science. My task is to view the human body as I would a squirrel’s body or a walrus’s—no, like a squirrel’s body: with candid dispassion.

VARIATION IN STATURE

So from the top, which is high. Since my legs lengthened in my early teens, I have been at the bottom of the cheerleading pyramid, the back of the chorus risers, the end of the line from short to tall. Again, not normal. But there is a good explanation or two. New research is taking old beliefs about human size and standing them on their head.

Early students of human anatomy believed some groups of humans were genetically tall, while others were genetically short. A dearth of data handicapped those early students, blinding them to a central fact of human height: It changes. I don’t mean that your height and my height change. Rather, the average height of entire groups of humans grows and shrinks with the passing decades. Since that timescale is too short to be the work of evolution, some portion of human height must be determined by the human environment.

A vivid case of this is found a few centuries back, when European humans migrated to the shores of North America. The race that was already in that territory, now known as American Indians, were among the tallest humans on the planet. Males of the Cheyenne tribe averaged five feet ten inches. Why? They enjoyed low population density. They ate a high-protein, low-fat diet of wild greens and buffalo. Their water must have been fairly clean, keeping digestive ailments and parasites to a minimum. They were, in a word, nourished. The migrating Europeans were not.

I wish I knew the height of my ancestors when they arrived, some of them in the late 1600s. Most of them were well funded and well fed, so perhaps they weren’t as tiny as the average. Columbus’s countrymen (the males) averaged five feet six inches. It’s lucky for those European migrants that they had mastered metal tools, because if the stunted specimens had arrived unarmed, they would have been laughed right back home by the strapping locals.

Even if my successful, blond ancestors were tall, I doubt they were the giants we are today.

A wondrous thing happened to those stunted European migrants: Once they took root, they shot up like weeds. Two centuries after Captain John Smith (five four, perhaps) dropped anchor at Jamestown in 1607, the average U.S. male had gained two or three inches, depending on whose data you use. After the European migrants learned how to grow food in North America, the offspring of new immigrants would gain an inch in a single generation. And today they may gain more than that. Some recent migrants from Guatemala have averaged an increase of 2.2 inches in a single generation. In every case, the cause is the same: better food, fewer stunting diseases.

And we’re still gaining. National food shortages during World War II meant both my parents lived through a period of food rationing as children. If that means they were undernourished you wouldn’t know it from their height. Dad made it to six three. My brother gained an inch on him, though, suggesting that something held Dad down. Mom, who lost some height to the old-fashioned polio virus, is another long drink of water. My sister and I didn’t gain any altitude on her, even though we ate a farm-grown diet and evaded polio. The length of my skeleton may represent the full genetic potential of my DNA.

So the height of the human animal waxes and wanes with the quality of its food supply. The case in point: Recent decades have brought improvements to the formerly fetid territory of Europe, from whence my ancestors fled. Dutch males are now the tallest humans on the planet, averaging five feet ten inches. Why Holland? With socialized medicine and financial support for the poor, the Dutch culture ensures that the offspring of all parents get sufficient calories and sufficient protection from disease. Thus each individual comes closer to reaching his potential. (They may still have a ways to grow. Some scholars expect the Dutch to rise another four inches before they hit their genetic ceiling.) By contrast, in my culture food and medicine are shared less equally, with many of our young failing to find healthful food and medical care. Thus poor humans on average are an inch shorter than rich ones in my culture, depressing the national average. And obviously, in realms like Guatemala and Bangladesh, where the distribution of food and safe shelter is more uneven, human height is severely stunted. Sometimes, a discrete event is enough to push human height up or down. Europeans shrank during the Little Ice Age of the 1600s when crops failed. Japanese humans lost height in the hungry years after World War II. We would need a few generations of ideal nutrition for all the world’s humans before we could see what the underlying genetic height of various populations might be. For now we can say that the height of the human animal varies by race, from four feet eight inches in male Efe Pygmies of Zaire to five feet ten inches in the Dutch.

The human female is, on average, a few inches shorter than the male. This is a telling detail. Often, a sharp size difference between sexes indicates a violent relationship between males. The goal of a male gorilla, for instance, is to wage war against all other males to control a group of females. The losers don’t get to breed. As a result of their high-stakes mating system, male gorillas have evolved to nearly twice the size of females. Chimpanzees live in looser groups with more mate mixing, and the males are just 20 to 30 percent bigger than the females. And among humans, who are somewhat monogamous (we’ll test that in chapter 7), males are just 10 or 15 percent larger than females.

When an animal species displays this sort of “size dimorphism,” it’s usually the male who’s biggest. Females usually opt to stop growing and start reproducing, whereas males are forced to grow, in a sort of arms race with other males. But occasionally size dimorphism swings in the other direction. The female spotted hyena is one of the most butch chicks in the animal kingdom. This girl is generally 15 percent bigger than the males, who cower in her presence. Her modified clitoris is about the size of the male’s penis. She pees through it, mates through it, and even gives birth through it. (I can hear you wincing, gentlemen.) Although rare, this reversed size dimorphism can evolve if the female is the defender of a territory; or if her method of reproducing demands room for storage of eggs or fat; or, as is suspected of the hyena, a mutation of the hormonal system blitzes a female with extra testosterone.

In some animals, size dimorphism can go to grotesque extremes. Among many spider species the males are so small they could be mistaken for prey. The minuscule males of some orb-weaver spiders have evolved to strum a lady’s web threads in a special tune that goes, “I’m not a gnat.” More creepy are angler fish, who live at remote depths of the ocean. In most angler species, when the dinky male locates a female, he latches on. He latches with such conviction that his head more or less dissolves and he becomes a sperm-generating tumor with fins. (I can hear you wincing, ladies.) Sadder still is a species of deep-sea worm in which the eggish male, who is little more than a yolk-sucking sack of sperm, whiles away his entire life deep in the female’s gut.

SCANTILY FURRED

At the very summit of the elongated animal before me is a shock of pale fur. There’s quite a lot of it, sprouting from my skull like a lion’s mane. It drapes down my back between my shoulder blades and comes to a stop where a groomer has snipped it. How long it would grow is anyone’s guess. Each human’s follicles are programmed to grow a hair for a set number of days before resting, then producing a new one that ejects the old. Both my sister and mother have allowed their fur to grow unsnipped, and their manes proved quite different. My sister’s fades out at the shoulder while Mom’s stretches halfway down her spine. Mom, whose follicles must be near round, grows the straightest mane; my sister’s follicles are moderately flattened, producing curly fur; and my own follicles must be right in between.

That’s what my fur looks like. But what is it for? Given the general nudity of the animal before me, half of my head is a surprising place to let loose with the fur making. It looks like an accent, like the mane that advertises a lion’s masculinity, or the white tuft on a tamarin’s head that helps fellow monkeys follow her gaze. Except that my fur serves neither purpose. It even impedes my view sometimes, an undesirable feature when tigers are stalking me, or tamarins are pointing their tufts at a jaguar.

The patchy pattern of human fur has yet to be explained by science. No one knows why long “terminal hairs” sprout mainly from my head, eyebrows, and the base of my limbs. Why am I not fully pelted, like a normal mammal? Stepping closer to the mirror, I’m reminded that I do, in fact, have fur all over. For one thing, my arms and legs sport a shimmer of terminal hair—sturdy, colored fur. And on closest inspection, tiny, transparent “vellus hairs” sprout from millions of follicles, head to toe. Vellus hairs are their own itty-bitty things, visible even on the silken underside of my wrist if I hold it correctly against the light. And they’re fur. (I brace myself for the wrath of poodle owners everywhere when I assert that all fur is hair, all hair is fur, and even the quills on a porcupine and the scales on a pangolin are hair/fur. It’s the same stuff.) All together, I have more fur follicles than a chimpanzee has. Furthermore, my pelage even attempts to keep me warm, retaining the piloerector muscles that hoist my hairs aloft when, for instance, I stand buck naked in a dim and chilly hallway in the name of science.

So perhaps the question isn’t “Why no fur?” but rather “Why has the human pelt shrunken to something that wouldn’t cover a mouse’s modesty?” And that question reels us back to the dawn of humanity, when the hominids split from the other apes in our family tree. Six or seven million years ago, one ape species split into two species. One of those two new apes went on to diversify into today’s great apes—the gorilla, the bonobo and chimpanzee, the orangutan—all of whom retain a respectable coat. The second evolved into the final great ape, me, the funnily furred. What event in proto-human history encouraged our kind to shrug off the body coiffeur?

And the answer is… Who knows? Our ancestral hominids left no written record of their lifestyle, and their fossilized skeletons are mum on the subject of how furlessness might have contributed to their survival. So when and why the fur shrank to this extravagant topknot remains a riddle. And that’s the sort of knowledge vacuum that causes theorists to bubble with theories. Among them:

We were so large bodied, and our environment so warm, that fur made us overheat.

One of the sexes admired nakedness in the other, causing both genders to evolve toward nudity.

Furlessness is a side effect of “neoteny,” the human tendency to retain childlike features (like oversized heads and lifelong inquisitiveness)

During an alleged aquatic phase in human evolution, body fur was, literally, a drag.

We had to throw out the baby—our protective fur—to dispose of the bathwater—parasitic ticks and lice.

The first theory is the most popular. It relates to early hominids adapting to a new environment when they left the forest and took to the plains of Africa in pursuit of animal foods. If at first they galloped on four legs, then the fur on their backs protected them from the blazing sun. But eventually, to improve their hunting success, they evolved to scamper about on two legs. Over eons, they developed a profusion of sweat glands. (We inherited from these ancestors more sweat glands than any other critter on Earth—a few million.) Sweat cools an animal with tremendous efficiency, if it can evaporate quickly into the air. Because fur slows this sweat cooling, my ancestors gradually shed their fur, laying their damp skin bare.

This “sweat theory” suffers fewer soft spots than competing theories. For instance, if shedding the pelt foils parasites, why haven’t more mammals done it? Or, if furlessness was meant to speed swimming, why have seals and otters retained fur? And why didn’t early humans re-evolve fur when they rejoined th...