The Well-Dressed Ape E-Book

Hannah Holmes

• Herausgeber: Atlantic Books
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Veröffentlichungsjahr: 2009

Beschreibung

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.

Leseprobe

Copyright

First published in the United States of America in 2008 by Random House, an imprint of The Random House Publishing Group, a division of Random House, Inc., New York.

First published in Great Britain in hardback in 2009 by Atlantic Books, an imprint of Grove Atlantic Ltd.

Copyright © Hannah Holmes, 2008

The moral right of Hannah Holmes to be identified as the author of this work has been asserted by her in accordance with the Copyright, Designs and Patents Act of 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of both the copyright owner and the above publisher of this book.

Every effort has been made to trace or contact all copyright-holders. The publishers will be pleased to make good any omissions or rectify any mistakes brought to their attention at the earliest opportunity.

Atlantic Books

An imprint of Grove Atlantic Ltd

Ormond House

26–27 Boswell Street

London

WC1N 3JZ

www.atlantic-books.co.uk

First eBook Edition: November 2009

ISBN: 978-1-848-87433-6

IN MEMORY OF MY DAD

Dr. P. K. Holmes

A BIOLOGIST IN THE LARGEST SENSE OF THE WORD

Contents

Cover

Copyright

INTRODUCTION

1: QUICK AS A CRICKET: PHYSICAL DESCRIPTION

2: CRAFTY AS A COYOTE: THE BRAIN

3: BLIND AS A BAT: PERCEPTION

4: FREE AS A BIRD: RANGE

5: A DOG IN THE MANGER: TERRITORIALITY

6: HUNGRY AS A WOLF: DIET

7: LOOSE AS A GOOSE: REPRODUCTION

8: BUSY AS A BEAVER: BEHAVIOR

9: CHATTY AS A MAGPIE: COMMUNICATION

10: TOUGH AS A BOILED OWL: PREDATORS

11: A BULL IN A CHINA SHOP: ECOSYSTEM IMPACTS

EPILOGUE

ACKNOWLEDGMENTS

SELECTED REFERENCES

INDEX

INTRODUCTION

I am one of those people with a reputation for being a “natural” with children. Because I produced none of my own, my friends often make the observation with an air of puzzlement, after I’ve beguiled their offspring out of a sulk or into a game quieter than hurling pot lids.

The honest explanation has seemed too impolite to share: Of course I’m fluent in child. I’ve spent my whole life around wild animals.

I grew up on a small farm in Maine, but livestock was only part of the picture. Besides the domestic cows, pigs, horses, and chickens, we always had a few wilder species, too. In a town without a veterinarian, my parents, both of them biologists, stood out as the experts in broken wings and orphaned babies. Things arrived on the doorstep. Among the family photos is a portrait of me as an infant with a sparrow named Maybe on my head. Maybe, named for her odds of survival, matured and moved outdoors, but would hop up and down on the door latch to come in for a visit. Wowl was an elegant little screech owl who would ride our shoulders, his claws piercing through our shirts while he preened the tangles in our hair. There was a chipmunk named Tammy who lived in a cage in the bathroom, opposite the guinea pigs. They were joined at some point by a flying squirrel, the softest animal I’ve ever known. Sleepy in the daylight, he’d bumble down inside our collars to ball up in the hammock where shirt tucked into jeans. At night he exercised by sprinting across the floor and up the wall, then kicking off to sail across the room. An ominous silence settled over the bathroom community when a great horned owl arrived for rehab. Confined to an old barrel to keep him from flapping a broken wing, he clattered his scimitar beak whenever humans invaded his territory to take a pee.

We children soon built our own menagerie. The robin who fell from his nest would wait on my shoulder when I shucked corn, eager to peck worms from the cobs. My brother kidnapped a European starling from a hollow tree, rearing it in a berry basket by the window. My sister filched a warm seagull egg from its nest, and the bird and the girl spent a storybook summer together before the adolescent bird would no longer fly home from the shore when she called. Twice I raised orphaned raccoons, which are endearing little bundles of spring steel until they grow up and become large, scary bundles of spring steel. So I know animals. Animal behavior and body language are so legible to me that it demands no conscious effort to interpret it.

This is why I don’t find children baffling. They are young animals, unrefined in their instincts and impulses. If an animal is shy, I don’t gaze or grab at it, because those gestures are predatory. Instead, I avert my eyes and display something enticing. To avoid frightening the young human who has approached, it’s essential to project positive feelings. When a horse detects the stiffening of a fearful rider, the horse tenses because it has evolved to respect any indication of danger. Inversely, a fearful horse can be soothed by a rider who is at ease. And so it is with the young human: He monitors other humans for hesitations, signs of doubt, signs of danger. I try not to embody any. Thus, by exploiting an animal’s instincts, it’s possible to manipulate its behavior to suit yourself.

Of course, there are differences between children and chipmunks. For one thing, human young are experts at learning. And once they learn they’re being manipulated, they often rebel. Second, as humans mature, our enormous brains allow for enormous differences in behavior from one of us to the next. When you wish to manipulate the behavior of an adult human, it becomes more efficient to reason with the animal than to exploit its basic instincts.

Despite the way my early experience with animals has deepened my understanding of humans, I grew up believing a bold line separated my species from all others: There are animals, and there are humans. After all, in my everyday world, the complexity of human behavior underscores our uniqueness and distracts us from the universal traits that unite humans with all other creatures.

But then, for a previous book, I spent a year studying the small ecosystem of my backyard. I got to know my local squirrels and crows, worms and ants, and learned how they all interact with their environment. It wasn’t until the end of that book that I circled around to the animal that is me. What are the differences, I began to wonder, between children and chipmunks? I mean, what are the real, biological, brain-ological, immutable differences? And more intriguing, what are the real, biological, brain-ological, immutable commonalities? It was then that I realized I’d never seen a biological fact sheet on the species we call Homo sapiens. And that struck me as strange.

Whenever biologists discover a new animal it’s their custom to crank the creature through a factual sausage grinder, producing tidy links of information. With academic detachment they tabulate the number of legs and teeth, note food preferences, and characterize habits of reproduction. A porcupine, for instance, emerges with a fact sheet something like this:

PHYSICAL DESCRIPTION: This is a fifteen-pound mammal with big teeth and little eyes. Specialized hairs on the back puncture the mouth of predators.

HABITAT: The animal prefers to feed in treetops but will also browse on the ground. It rests in rock burrows when available.

RANGE: North America, including the tundras of Canada and Alaska.

BEHAVIOR: The animal is nocturnal and mostly solitary. Contrary to myth he cannot hurl his quills; in fact, he can become stuck to his victim when the quills refuse to separate.

REPRODUCTION: Precarious.

And so on, addressing the animal’s perceptive senses, communication, diet, environmental impacts, and predators. Every species chugs through the same machinery, emerging as a standardized profile. The fact sheet is a handy way to summarize an animal’s place in the web of life.

I’ve read hundreds of these, describing everything from the three toed sloth to the nine-banded armadillo and the thirteen-lined ground squirrel. But I’ve never encountered a full description of the two-legged ape. We Homo sapiens, so eager to describe the rest of the world, have been chary about committing our own natural history to paper.

This seems unfortunate. For one thing, it reinforces the notion that we’re not normal animals. It lends the impression that we’re too wonderful to summarize; that although the giraffe can be corralled in paragraphs, the human cannot. That’s unfair to other species. On the flip side, it suggests we’re misfits, as animals go. It lends the impression that we’re not worthy to take our place beside the gemsbok and the gorilla; that we are excluded from the brotherhood of mammals. This is unfair to my species.

It also seems unnecessarily dour. What could be more fun than describing the human, after all? What color would you consider the animal to be? Regarding diet, is there anything on Earth that we humans won’t put in our mouths? As for communication, does my smile or my outstretched palm send the same message as a chimpanzee’s version of those gestures? Can the human mate with any other species, the way donkeys can mate with horses, or lions with tigers?

A proper description of the species will answer these questions, and some larger ones, too: Who are we, animally speaking? Sure, we’re clever—but compared to what? Yes, we’re obsessed with mating, but any more or less than other animals? And our males behave quite differently from our females—but is that unusual? Are humans apex predators like lions or bears, or do we have to watch our backs like gazelles and rabbits? Can we survive as high in the mountains as mountain goats? And if we can, how many square miles does each human require? Sure, we communicate a great deal, but so do parrots and prairie dogs. Our behavior is tremendously tool centered, but the list of other creatures who make and wield implements is growing steadily as we watch them more closely.

Happily, the human (and only the human) delights in analyzing itself. Giraffe nor Gila monster will spend time with chin in hand, watching her neighbors and wondering. But humans analyze ourselves for the fun of it. We, and only we, want to know where the child and the chipmunk overlap, and where they diverge.

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 the land mammals? The few bald mammals I can think of—elephants, rhinos, walruses, and whales among them—tend to be large, lending credence to the sweat theory. Because those species aren’t endurance athletes, they sweat modestly, if at all. But the human, built for distance, sweats buckets. In sogginess per inch of hide, the human animal is bested only by the horse. And that’s because the horse’s northern range forces it to wear fur, which in turn necessitates heavier sweating. We tool-crazy hominids, by contrast, as we expanded into the horse’s snowy latitudes, invented clothing, a layer of insulation that can be donned and doffed at will. Because we have tools, we don’t need fur; and because we lack fur, we enjoy world-class cooling.

This explanation neglects the problematic hair on my head, though. The best theory here relates to my massive brain (which we’ll get to soon enough). Theory goes: The head of my ancestral hominids, as they reared upright, was exposed to the tropical sun. As the brain of hominids evolved larger, this head fur grew in importance. A brain is a steaming wad of fat, a three-pound radiator. It’s vulnerable to high temperatures and will fry out at 107.6°F (42°C). So it’s insulated against the sun with a mop of fur, and it’s cooled with a surfeit of sweat glands. That’s the predominating theory, anyway: We shucked the body fur in order to cool our bodies better, but kept the head hair to prevent the brain from baking. My tresses shield my brain from the sun, the way a sheep’s fleece keeps it cool in the desert. And the rest of my skin is open to the wind so I can sweat cool as I sprint after hamburgers on the plains of South Portland.

My mate, stripped down, is furrier than I am. Terminal hairs, powered by testosterone, sprout from his cheeks, jaw, neck, and chest, in addition to the tufts at the base of his limbs. Why males are furrier isn’t clear. It could be that females have long preferred furry males, which resulted in furry ones outbreeding less-furry ones—a phenomenon known as a “sexual selection.” The peacock’s tail probably evolved thus: It has no function beyond looking fabulous. (The fact that many cultures currently abjure body fur on both females and males is immaterial—or not: If females were to abjure it for many generations, males might evolve to be as furless as females.)

Sexual selection would explain why fur patterns vary even from one region to another. As a rule, pale humans who evolved in Europe and the Middle East are hairiest, while south and eastern Asians, American Indians, and west Africans rank among the smoothest— some males lack facial hair altogether. It may be that countless generations of Middle Eastern females preferred their males furry, while Asian females spurned the hirsute suitors. Also arguing for sexual selection is the fact that human fur erupts from our most odiferous body parts only as we reach breeding age. In humans, the apocrine glands concentrate at the base of the limbs and around the nipples on the chest, releasing fatty substances onto the hair shafts there. Although proof is slim, it’s a reasonable thesis that the fur tufts on my body help to distribute my unique odor to potential mates. (What my mate can read in my odor, if he can detect it at all, is a question we’ll tangle with in chapters 3 and 7.)

COLORATION OF SKIN AND FUR

If the distribution of my fur is a puzzle, its color is another. Mine resembles a field of dry grasses. “Applewood” was my grandmother’s term, derived from the light and dark streaks in the tree. “Towhead” was my grandfather’s term, a reference to the color of tow, aka flax, aka dead grass. Like my pale skin, pale fur is a radical departure from the prototype. Humans are thought to have evolved on the brightly lit savanna, where we adopted a dark hide under the dark fur that chimps and gorillas still boast. To this day, brown or black fur is the norm for humans in the latitudes where our species evolved. It’s the groups that hiked out of Africa, and adjusted their tint to other climates, who need to explain their appearance. So, with no further ado, my wheaten locks drag me into the field of race.

Well, with a little ado: Many evolutionary biologists now assert there’s no such thing as race, as different strains of humans. They argue there is more genetic variation between two northern Europeans, like me and my mate, than there is between me and my Mongolian friend, Bolortsetseg. This is, to my mind, a mathematical gimmick. Certainly, Bolor and I share oodles of genes that regulate our kidneys and our fingernails. Those fundamental features aren’t subject to the climate pressures that drive evolution. But most humans, including me, can effortlessly pick out where Bolor’s and my genomes differ, too. We can look at ourselves and see something that’s eluding the theorists: Whatever differences do exist in our DNA, they’re having a big impact on the way we look. They’re affecting not just skin colors, but entire suites of characteristics, involving eyelids, noses, lips, skin, hair, and even body shape and size. And if we’re like every other animal on Earth, we came by many of these differences honestly: Groups of isolated humans evolved in distinct environments, which rewarded distinct arrangements of their DNA. So, while one scientist has characterized racial variation in the genome as being “scientifically and mathematically trivial,” these differences are certainly not ecologically trivial. The relationship of a human body to the habitat in which it evolved—or in which many generations of its ancestors evolved—is far too marvelous to ignore. Besides, we humans view other animals in exactly this way: as races, different in color, shape, size, and geography, but grouped under one species. For instance, the black bear in Florida weighs three hundred pounds and eats lots of vegetation, while the black bear in Newfoundland weighs four hundred pounds and eats moose and caribou, and the black bear in Alaska is often brown.

Now, back to my distinct shape and color, which I insist do exist. In the mirror, my skin is pale, which unkindly accentuates every bump and blemish. This is typical of the northern European package. My skin is pale, my fur is pale, my eyes are pale, my nose is long, my cheekbones narrow, and my lips thin. I’m close to the palest end of the human spectrum. But the European human is unusual in that it comes with a lot of color options. Within my immediate family the skin is reliably pale, but I can find eyes in brown, green, and hazel, and fur that’s reddish, brown, and nearly black. This grab bag may be related to the varying levels of melanin in the northern animals, or it could relate to a few freakish but harmless mutations. Pretty much all the other groups of humans on Earth have retained brown eyes and dark fur.

So why is my face so wan compared to humans from Africa, India, and Australia? Considering how long the subject of skin color has transfixed humanity, it has taken a very long time for a solid theory about it to emerge. Until recently, the best guess was that dark skin dominated at the equator to fight skin cancer, and pale skin evolved to the north and south to hasten the body’s manufacture of vitamin D from scarce sunlight. But skin cancer is a red herring. It takes so long to develop that most victims don’t perish until after they’ve raised offspring. It should have no effect on evolution.

Vitamin B, or folate, is a different story. It has inspired Nina Jablonski, a pale, American paleoanthropologist, to pen a robust proposal. She and her coresearcher-mate began with one of the human animal’s more advanced tools, an orbiting satellite that looks down to measure the amount of ultraviolet (UV) radiation reaching the earth. Equipped with a map of UV intensities, they next set out to see what shade of human skin has evolved under the brightest spots and the dimmest. Then onto that map they plotted the color of human hide. And yes, human skin is darkest where UV is the strongest. But skin cancer is not the reason, Jablonski says. Folate is.

The human acquires folate through the diet. But when UV radiation penetrates the skin, it breaks that folate apart. Human females with folate deficiency are prone to miscarriage, and their surviving offspring can suffer fatal nerve damage. Males deficient in folate produce lousy sperm. These are the sort of effects that steer evolution. As hominids evolved under the African sun, those individuals who chanced to have more melanin in their skin were protected from UV and maintained healthier levels of folate. They produced more offspring, and thus won more chances to send their genes forward in the human race.

So, if the need to protect folate rewards dark skin, then what caused melanin to wane in humans like my ancestors, who migrated to gloomy spots on the UV map? Well, the human animal has a conflicted relationship with sunlight. As much as we need to keep UV out, we also need it to penetrate the skin for the manufacture of vitamin D. Vitamin D is crucial to the construction of bones and to healthy blood chemistry. We must have it, and the sun is the source. So, Jablonski concluded, human skin color strikes a fine balance. It must be dark enough to preserve folate, yet pale enough to produce vitamin D. It’s a tidy theory: In sunny places, humans can afford dark skin because they’ll still get their vitamin D. In dim spots, the threat to folate diminishes, so skin can afford to lighten. It even explains why the skin of females is generally a shade lighter than males’: Females need more vitamin D to build offspring and nourish them with milk. (I suppose it might also explain the dearth of female facial hair: If I had a beard, it would reduce my D-building capacity.)

The UV map doesn’t predict human skin color perfectly. Occasionally, Jablonski found light-skinned humans in high-UV zones and dark-skinned humans in dim latitudes. Some mismatches result because our restless species has wandered to a new habitat so recently that we haven’t yet evolved the ideal coloration, Jablonski says. (English migrants to Australia, for instance, have yet to adapt to the intense UV there. They presumably enjoy indestructible bones, but they also suffer terribly from melanoma.) In other cases, such as the dark-skinned Inuit, the diet may be so rich in vitamin D (from fish) that skin can afford to stay darker, safeguarding folate. So my ghostly skin is a certificate of authenticity: I’m adapted to the cloudy climes.

If I accept that humans come in distinct varieties—and I do—then what shall I call them? Are my Mongolian friend and I two different “subspecies” of Homo sapiens? That’s the term biologists use to designate groups of animals that look a bit different but easily interbreed. For instance, the red-tailed hawk, Buteo jamaicensis, which is native to the Caribbean and Americas, splits into sixteen subspecies, including B. j. calurus, whose head is solid brown, B. j. kriderii, who’s pale all over, and B. j. harlani, with a mottled breast. None of these is more or less a red-tailed hawk than another. They’re just, you know, different.

Or perhaps Bolortsetseg and I are two “morphs.” When individuals within a species differ mainly in color, biologists use this term. Many hawk species come in two color morphs, light and dark. The North American gray squirrel sometimes turns out black. A jeweltoned toned Australian finch is available in three color morphs: with ruby face, orange face, or black face. Domesticated animals are more flamboyant in their morphic variety. For instance: We’ve bred dogs to vary from the size of a pony to the size of a breakfast pastry. We’ve created domestic rabbits in every natural hue, and with ear styles that wouldn’t pass the laugh test in the wild.

So what word suits? “Morph” seems too small to cover the many differences between Bolortsetseg and me. Our coloration differs strongly, but so do more structural elements, like our cheekbones, noses, lips, and eyelids. But the word “subspecies” suffers from the fact that Homo sapiens is a status-conscious animal, and none of us wants to be a sub-anything. I’ll try to make peace with the word “race,” in the fluid spirit of UK biologist Armand Marie Leroi. He refers to the concept of race as “a shorthand that enables us to speak sensibly, though with no great precision, about genetic rather than cultural or political differences.”

In recent centuries, humans have typically discriminated among three races of modern Homo sapiens: Asian, Black, and Caucasian. But most humans can spot finer divisions within these ABCs. To my eye, my own British Isles features look more lumpy than the angular faces of the French, but a bit less lumpy than the features of pale-skinned Russians. Likewise, to my eye, Australian Aborigines, with strong brow ridges and wide noses, look completely different from heartfaced Bushmen of southern Africa, who in turn look totally different from the diminutive Baka Pygmies of Cameroon. It’s this finely divided concept of race that Leroi champions. There are, he argues, as many races as you need to parse out in order to discuss human variation.

It works for me. Under this paradigm I can call myself a member of, from smallest subset to largest, the British Isles race, and the northern European race, the Caucasoid race, and the human race. It’s imprecise, fluid, and maybe even politically incorrect. But it’s an honest reflection of how my skin, fur, and facial bones took shape in an isolated pool of humans breeding in a cloudy, cool environment.

The subject of human diversity churns with emotion, but plenty of other animals have also evolved distinct races in distinct environments. The races of red-tailed hawk vary not just in color, but also in size and breeding habits, depending on the pressures of the environment. The tiny leopard cat, a mottled beauty who roams much of Asia, comes in eleven subspecies, with camouflage fur that runs from gold in the south to gray in the north, and whose size in the coldest part of its range is one-third larger than the southern races. The green-backed heron, whose range circles the tropics, is available in a bewildering twenty to thirty races. Whenever a population is isolated, it will continue to evolve, drifting slowly out of similarity with the other populations of its species. My lowmelanin face is proof.

I’m not making great speed down the body in the mirror, but I suppose that in a hominid the action concentrates at the top. I’ve ruffled my fur and pondered my pallor. The next obvious feature is, well, my features. This cluster of apertures does so much work that it’s best to skip past them for now and come back to them in chapter 3. For now, suffice it to say it’s no accident that four of my five major sensory organs are crammed together in my head. It’s human habit to think of the ears, eyes, nose, and mouth as “the face.” But taken separately, each is a sensor: My eye is a moist camera, my nose protrudes to sample the air, my ears funnel vibrations into my head. That face in the mirror is really a cluster of tools gathered around a motherboard, a CPU, the brain. And in the human, the brain, too, deserves a chapter all its own. In terms of the vision before me in the mirror, the next specialty of my species is the trait that puts the “mamm” in mammal.

PROMINENT MAMMARY GLANDS

Departing from the crowning glory, we slide down the neck (I’ll revisit that feature in conjunction with the legs and posture). And we quickly run aground on a blatant discrepancy between males and females—a pair of blatant discrepancies, really. Were my mate here beside me, we would see his two nipples sitting flat on his pectoral muscles, useless as an eye on the bottom of a foot. Formed early in the life of a fetus, nipples appear on most male mammals. (This may be a fillip of evolution, a mutation whose cost is so petty that a nipple-free male would have no advantage over a nippled one, and hence could make no evolutionary headway.) But here on my female chest, each nipple sits atop a hemisphere of fat. These fat stores wobble when I walk, joggle when I jog, and generally call attention to themselves. They, along with my waist-to-hip ratio, can telegraph my gender to an observer a hundred yards away.

Whether that’s why my enlarged glands evolved is open to debate. The human female’s mammary glands are, like the human fur pattern, another oddity of the animal kingdom. In most mammals, the milk glands swell only for as long as the mother is nursing young. When the offspring are weaned, the glands deflate and get themselves out of the way. Mine, which materialized along with my other secondary sex characteristics (tufts of fur, a wider pelvis, fat pads on the thighs and buttocks), are always puffed with fat. I see no advantage to this arrangement. I could easily store this fat in a thin layer under the skin or on my thighs. And, therefore, it is quite likely that the whimsical force of sexual selection has been at work. My puffy breasts may be announcing to the world’s males that I have garnered sufficient fat to support hearty offspring. Evolution would reward this architecture if my in-your-face advertising attracted a better selection of males. The ability of larger breasts to store more milk might also drive evolution: Largebreasted females can stretch the time between feedings of an infant; that, in turn, reduces the frequency of the infant’s distress calls, which reduces the chance of a predator hearing and locating the infant. In that case my lineage might be in trouble. From the look of things in the mirror, my offspring would issue frequent distress calls. But perhaps the trade-off is that I, relatively unencumbered, would be able to pick up the young squawker and run like the wind, if we attracted any predators. The least favorite theory I come across belongs to dear Desmond Morris, who in his classic Naked Ape proposes that breasts evolved to mimic buttocks, thereby to inspire a male’s mating urges from both front and back. It’s my humble opinion that mammary lust is a cultural phenomenon. It’s my humble observation that in cultures where clothing is minimal—the Yanomami of the Amazon, the Himba of Namibia, the French on the Riviera—it’s really only the mating parts that humans specially strive to obscure.

But in my culture most females keep the mammary glands under wraps. I’m getting self-conscious. Let’s exit my cleavage, what there is of it, and descend to the abdomen.

DISTRIBUTION OF STORED ENERGY… OKAY, FAT

Sliding downward from my narrowed female waist, we arrive (sooner than I’d prefer) at what a physiologist would call my “primary energy-storage tissues.” It is not an accident that my hands hang so as to block my (your—everyone’s) view of these tissues. Within my culture, these tissues are mortifying. My animosity for body fat is a recent development in human history. But we’ll examine that in chapter 6. Here, I shall try to cultivate an appreciation for lipids—not just for how they serve the human animal, but also for why they agglomerate where they do.

Fat is not, after all, gratuitous. The glorious human brain can’t function without cholesterol, a special fat cooked up by brain cells and the liver. Throughout the body, additional cholesterol insulates the nerve fibers and builds cell membranes. It’s also key to the manufacture of the sex hormones I wouldn’t want to live without. And that’s but one form of fat.

More prosaic is this layer that wraps my hips. This stuff is just a mass of specialized cells, called adipocytes, each holding a droplet of oil. When I eat more food than my body can use, it’s converted to oil and stowed in an adipocyte. Evidently I’ve done this a few times. Then when I eat less than I need, oil is pulled from storage, and burned. This stored fat of mine is like a bank account. And for all mammals, there’s a minimum below which the balance cannot fall without incurring a penalty. Most members of the warm-blooded crowd need between 4 and 8 percent body fat on hand to support normal activity and reproduction. I am probably carrying 30 percent, because… I need to have a cookie and think about that.

One reason I have so much body fat is that I’m female. A fit human male is about 15 percent fat, while a female, on whom offspring depend for nourishment, is 23 percent. I carry even more than that because… because cookies are too damned easy to capture.

Anyway, many humans no longer need to bank much more than the minimum of oil. Increasingly, we use tools to store food outside the body. This mimics one of nature’s classic strategies, whereby squirrels, mice, rats, and many other small critters stash food for later use. Most humans now use tools to preserve food, so that we needn’t forage for it in the wild. I might be a bit slimmer if humans had adopted the migratory method instead of the food-storage method. Animals like caribou, wildebeest, many birds, and even whales have evolved to migrate around the globe in pursuit of a shifting food supply. As food fades in one part of the world, they travel to where it’s flourishing.

Alas, although we’ve learned to cache food, humans still behave like one of nature’s true fatties. A few animals have adapted to pack a prodigious lunch under the skin, then live off it for months. The camel, some bears, the hedgehog, the badger, and migratory birds can become naturally obese. What these pudgers all have in common is a sporadic food supply. They make hay while the sun shines, and they carry that hay with them through the stormy weeks and months to come. They’re as adept at fasting as they are at feasting. Although humans have proven to be prodigious feasters, the fasting part we just can’t master.

If I had the lifestyle of a polar bear, my excess stored energy wouldn’t be a problem. During the winter sealing season, these animals accumulate a spectacular burden of fat. The sea ice melts in spring, forcing the bears onto terra firma, where they enter a dopey “walking hibernation” to save energy. The fattest of the fat are the breeding females. A female who’s pregnant at this point faces a nine month fast during which she’ll gestate in a den, then give birth and nurse cubs. In preparation, she will pile on four hundred to eight hundred pounds of fat, and nearly become incapacitated. A pregnant female looks like a snowball.

I am not one of nature’s natural fatties. Because a human moves around more than a sleepy polar bear, the weight of extra fat taxes human joints. Because my body chemistry can’t adjust to excess fat, obesity threatens humans, but not polar bears, with cancer, diabetes, and heart disease. Unfortunately, the mere fact that I’m not designed for fatness doesn’t prevent me from swelling. I came into this world with a huge number of small, empty adipocytes distributed under my skin, between my muscles, and around my organs. They yearn to be full. I yearn for them to be empty. You could cut the tension with a butter knife.

It’s not just me. Fat “generally behaves in an unpredictable and inconvenient way,” writes fat scholar Caroline Pond, a lecturer at the Open University in the United Kingdom, in her book, The Fats of Life. From one human to the next, fat cells congregate in different patterns. The distribution of my energy stores is partly genetic. Among the females in my family, it’s common to store energy in the hips and thighs, and not in the mammary glands. But fat’s shape has a nongenetic component as well, leaving plenty of room for individual expression. We enjoy, in fact, more expressive fat than any other species. In other animals, fat behaves more predictably and conveniently.

My fat does obey a few rules. The most important one is that it must stay out of the way. I can’t store it around my neck, for instance, as that would hamper my ability to look down. It can’t swaddle my fingers, whose thin tips do delicate tasks. It mustn’t coat my head, lest my brain overheat. It mustn’t thicken the inner thigh, or my ability to chase prey will suffer. Given all these restrictions, one safe place for both males and females to stow fat is in a smooth layer, just under the skin.

Subcutaneous fat isn’t standard for mammals. We expect to see that layer on marine mammals like seals, orcas, and whales. But most others direct their fat to designated depots. The camel and the bison concentrate theirs in the hump; the beaver and the platypus fill their tails. The gray squirrel keeps half his total fat deep in the gut, and birds stack lots of it at the wishbone, perhaps to keep fuel handy for the wing muscles. Primates like chimps and gorillas favor fattening the paunch. Many other mammals lay in a pad of fat over their shoulders. Although mine congregates on the hips, it also pads the entire underside of my hide.

The anomaly of my subcutaneous fat helped inspire one of the weirdest theories in human evolution. Try as I might, I can’t describe the aquatic ape theory with a straight face. Here it is in a nutshell: Somewhere back in the early millions of our humanhood, we took to the sea like so many otters. We caught fish with our… fingernails? (We had long since downsized the canine teeth that many predators rely on for fighting and feeding.) As this theory would have it, we lost our body fur because it retarded our swimming; for insulation, we developed a dolphinny layer of fat under the skin. We waded or swam after our prey, with only our furry heads protruding into the sunlight.

Now, I love dolphins as much as the next Homo, but this just doesn’t wash. For one thing, the fat layer on a human is most undolphinny. Real aquatic mammals like seals and whales are born with a sleek layer of fat, and they maintain it as they grow. (And it’s not for insulation, Caroline Pond suspects. Because marine-mammal fat is not distributed in a uniform layer, she guesses it has more to do with streamlining and fueling nearby muscles.) Human fat, by contrast, waltzes around the body during the course of a life span. I was a chubby baby, with fuel packed on to warm me and smooth my transition to nursing, which can take a few days to grasp. By age nine I was outgrowing my fat supplies so fast that I resembled a bicycle frame minus the padded seat. At eighteen, I began laying in fuel against those fat-draining tasks of pregnancy and nursing. And one of these years, my shifting hormones will move fat to my waist. I assure you, the fat topography of my mature body does absolutely nothing for my hydrodynamics.

There are other obstacles to my aquatic success, as well. My flat snout, even if it were fitted with respectable canine teeth, would expose my nose and eyes to thrashing prey when I hunted—unless I was a tool-wielding aquatic ape. And then there are my fingers, which aquaticists claim are webbed. In reality they do their best swimming when the alleged webs are tucked away between my cupped fingers. Regardless, the aquatic ape theory continues to cavort in the sea of ideas, apparently facing no imminent risk of extinction.

Back to my fat. In addition to the subcutaneous stuff, I bear some conspicuous bumps fore and aft. My mate’s fat gels elsewhere. His, what there is of it, pads the abdomen, as it does in other primates. Had he more, it might accrue on his shoulders and at the back of his neck. Caroline Pond speculates that females can’t deposit their healthy bank account of fat on the abdomen, as males do, because it might overheat a baking fetus. On the rump my fat is, if not out of mind, at least out of my way.

Pond also believes that my mammary-fat storage is not just sexspecific, but also sexy. Her theory flies in the face of the feminist argument that mammary glands are feeding appendages and not sex toys. The argument is intriguing: Just 4 percent of a healthy female’s body fat lodges in the mammary glands, on average. Yet this 4 percent makes a big visual bang for the buck. And that, Pond says, is a dead giveaway for a sexually selected feature: Like the nodding feathers on the head of a California quail or the dark mane of a lion, my bobbling mammary glands are more flashy than they are practical. Perhaps they signal my readiness to nurse young.

The final and most unfair difference between male and female fat storage regards the distribution of collagen. This pains me, but I’ll just come out and say it: The energy-storage tissue on my leg is dimpled. Probably for most of human history, and definitely in Renaissance Europe, this was considered a great asset. That was then. Biologically speaking, the dimples come from the female arrangement of collagen, the fibers that anchor skin to the underlying muscle, running through the fat in between. In a female leg like mine, collagen fibers pass through the fat in a straight line, like nails holding a mattress to a wall. But there are so few nails holding up my fat that the mattress sags in between them. Adding insult to injury, my female estrogen works on collagen over time, contracting the fibers. This exacerbates the bulging. In males, by contrast, the collagen nails crisscross one another, giving greater stability and smoothness to the mattress. Why did evolution lead me to this bumpy state? No clue. I suppose that thigh dimples, like breasts, could signal that a female has stored sufficient fat to grow a dimpled baby. Stranger traits, if not less fashionable ones, have evolved.

If there’s any justice in this fat situation, it’s in the way fat moves around as humans age. The majority of males will actually develop breasts of their own as their hormones drift toward a more female mix in old age. Of course, my own fat will migrate, too, deflating my hips and padding my waist out of existence. With time, the distant silhouettes of males and females come to telegraph the same message: past prime.

THE FORELIMBS, PRIMARY MEANS OF DEFENSE

Speaking of my hips, that hand poised to obscure my rump deserves credit for more than obfuscation. Why, that hand is also my state-ofthe-art weapons system—five sticks of thin skin and fragile bone, each tipped with a wafer of wannabe claw. I’m trying to count the times I’ve used it successfully. I guess I balled the hand into a club and knocked my brother down once. And I remember whacking a boyfriend who was breaking up with me in a spectacularly stupid way. In both cases, my assault was mainly intended to punctuate a barrage of verbiage I had wearied of. Which is about all my little sticks are good for. Until you give the human animal tools, it is pitifully armed, and not dangerous.

This isn’t normal, among primates. Cousin Chimp’s weapon of choice is his large teeth. A chimp attack on a human male in 2005 put this animal’s armaments on display. The human, a visitor to a private chimp sanctuary in California, was bitten almost to death. Two male chimps chewed off most of his fingers, his gonads, and much of his face, and they bit a foot clean off his body. The human survived, but probably only because another human attacked the two chimps with a deadly tool. Gorillas and orangutans, as well as the other primates, also rely primarily on their teeth to wound and kill their rivals.

A fighting ape or monkey will bite any bit of anatomy that presents itself. But he will make an extra effort to savage toes and fingers. And primates seem driven to damage one other appendage, as well. Time and again, biologists have noticed that scrapping males, if they get a chance, will slash at an enemy’s testicles. I suppose it’s a sound evolutionary strategy. If you can’t kill a rival, you might at least eliminate him from the pool of males competing with you for breeding opportunities.