Mankind

INTRODUCTION

AFTER THE EARTH COOLED ENOUGH TO FORM ITS UNIQUE CONFIGURATION OF ELEMENTS AND ATMOSPHERE, IT TOOK ANOTHER HALF BILLION YEARS FOR THE FIRST SINGLE-CELLED ORGANISMS TO BLOSSOM IN ITS DEEP OCEANIC VENTS, AND TWO BILLION MORE FOR THEM TO BEGIN TO DIVIDE AND DIVERSIFY.

From specks of star dust to single-cell life-forms, the evolution of the human race into a form recognizable as the species we are today began some 150,000 years ago.

Mankind has existed for a fraction of time in the history of the universe, and most of it spent in a life-and-death struggle for survival—with no guarantees of success at any point, not even the present.

Mankind: The Story of All of Us retraces the path of learning that made us masters of fire and iron, gave us the comforts of food and shelter, and remade us into inventors, builders, and space travelers. Perhaps the most unlikely accomplishment of all on our zigzag learning curve as a species is our survival. Surprise has been the only constant in human history.

If there is one key to our longevity, it has been our ability to adapt to frequent, often violent change. We have turned our most vulnerable weaknesses into strengths, beginning with our relatively small size and lack of speed compared to other mammals. Such an extreme physical disadvantage forced us to develop and employ bigger brains to outwit our foes, whether man, beast, or vast swings of temperature and climate.

A fair amount of luck was involved in humanity’s triumph over the astonishing odds wrought by ice ages. Mankind has faced predators five or ten times our size and strength. Also, unlike other species, we are born relatively fragile and unformed, requiring a long period of parental care that left our earliest ancestors vulnerable to violence, illness, and sudden death.

Physicist Paul Davis attributes our ability to persevere against these overwhelming odds to a chain of “Goldilocks moments” in which everything needed to help us adapt occurred exactly the way it needed to—or close enough to get us through another ten or twenty thousand years until a continent thawed or migration brought us closer to a vibrant river, the perfect prey, or a stretch of fertile soil.

Planetary and human history is traditionally presented in time lines lacking any visceral sense of the huge obstacles and near misses that pushed the human species to become smarter, more adept creatures. In third grade social studies, high school world history, or college surveys of Western civilization, a typical textbook follows an illusory linear progression. And while a time line can be a useful tool, it generally starts too late, since, in the context of the universe, we’ve been here barely long enough to catch our breath. Not only is the textbook time line too short; it is also too narrow, focusing with a few exceptions on humanity itself, with no reference to the world around us.

In fact, our history was shaped not just by our own actions, collective and individual, but also by incidents as large as a tilt in the earth’s orbit and as small as a genetic mutation in a grain of wheat. Human evolution has never been a forward march of progress consisting of evenly divided positive steps from archaic humans to their modern counterparts, each change in our appearance and behavior an improvement on the last. Several new hominid species coexisted in Africa between 2.5 million BCE and the arrival of modern man in 150,000 BCE. Which one would triumph and become our direct ancestor was far from settled as recently as fifty thousand years ago.

The majority of evolutionary changes have been relatively minor things—the refinement of an opposable thumb, a fractional increase in cranium size, the ability to stay upright long enough and stretch an arm far enough to grab a fruit from a low-hanging branch—the consequences of which play out incrementally over thousands of generations. This change in perspective does not detract from the significance of each Goldilocks moment. On the contrary, it underscores the precarious nature of the human drama: depended on the right behavioral adaptation meeting a hospitable setting.

In the chapters ahead we tell the story of pivotal points when natural forces intersected with human ingenuity and a bit of luck to make (or break) us as a species. In these times and places, the human race faced mysteries and obstacles so formidable that if they had not been solved and surmounted, chances are we would not be here today. By reliving these transitional events, we can better understand what our predecessors were up against when they made the huge leaps forward that ultimately ensured their survival—and set the stage for ours.

So we begin at mankind’s beginning, when staying alive translated into an unrelenting, often dangerous search for the day’s food.

1

SEEDS of CHANGE

Our early ancestors made the first tools more than 2 million years ago by striking one stone against another. Simple choppers evolved over the centuries into cleavers, hand axes and finely worked stone blades.

THE HUMAN RACE WAS BORN ON THE GRASSLANDS AND FORESTS OF AFRICA’S GREAT RIFT VALLEY, A FRACTURE IN THE AFRICAN CONTINENTAL PLATE WHERE DIVERSE ECOLOGICAL SYSTEMS AND human-friendly temperature ranges made it the perfect laboratory for the development of a hairless, toolmaking ape. It is here that we join human evolution reached its first critical pivot: the transition from ape to human.

We have no precise dates for such monumental advances in the human condition as hunting and fire making, but scientists have amassed substantial evidence about what life was like before and after these breakthroughs. These traces of early human history come to us as artifacts: tools, abandoned campsites, ruined villages, hidden art, and skeleton fragments.

In recent years, we’ve learned to read ancient artifacts more closely than we could in the past. Geologists study climate changes using drill cores from lake sediment. Paleobotanists trace the evolution of foodstuffs using fossilized pollen DNA testing and sequencing. Techniques such as biomechanical modeling of teeth and bone scanning give paleontologists and paleoanthropologists a window through which to view the relationships between humans and animals, and between humans and other humans, across time and space. With the help of these new technologies and methods, we are finding more and more that we are all part of the same whole.

On the most basic level of survival, we know that our earliest human ancestors were scavengers who foraged for fruit, nuts, and seeds. They ate birds’ eggs, termites and ants, and dead birds or animals, at least when they were lucky enough to find them. Even after someone picked up a rock, threw it at a rabbit, and invented hunting, most of the diet consumed by these small human bands—men, women with children, and extended family members—still came from their collective efforts at foraging for wild grains, berries, and roots.

But how long ago did mankind make its appearance? That depends on how you define being human. If you don’t stand up and walk on your own two feet, you’re an ape, not a human. And while there is no clear moment at which we can draw a line between apes and humans, the Human Genome Project repeatedly brings us one step closer. Historians and scientists now believe that the first protohumans appeared in East Africa as early as 5.5 million years ago, but they weren’t direct ancestors of early humans. Like modern apes, they could walk upright for a brief time if circumstances required it, but for the most part they were tree climbers and knuckle walkers.

The first true hominid—a member of the family Hominidae, which includes modern humans—showed up 2 million years later, around 3.5 million years ago. Paleoanthropologists call her Australopithecus, or the southern ape; we’ll keep it simple and call her Lucy.

LUCY WAS CLOSER TO AN APE than an early human. She stood only three or four feet tall and had a brain about the size of an orange. Her face was more like an ape’s than a human’s, her arms were longer than ours, and her fingers curled like those of a chimpanzee. She may have chosen to use those long arms to climb a tree, like an ape, but she had all the physical equipment she needed to walk upright on two feet. In fact, she was probably better designed for walking upright than we are. The human pelvis is a compromise between standing upright and giving birth to babies with large skulls and sizable brains.

Being bipedal has a major advantage: it leaves your hands free. Combine that with the opposable thumbs that small primates developed fifty million years earlier and you’re ready to pick up a tool. Lucy did. She probably didn’t make tools, but she used rocks and sticks to help her hunt for food and fend off predators.

After Lucy, our story gets more complicated. There may have been up to one hundred hominid species that coexisted in Africa between Lucy’s time and the arrival of modern humans around 150,000 BCE. We don’t know how they relate to each other, or which species we can call our direct ancestors, but after much controversy, anthropologists are in general agreement about two groups of proto-humans with whom they think we have more direct familial connections.

Homo habilis, literally the “handy man,” is considered the first protohuman, and he carries the distinction of being an adept toolmaker. He appeared in East Africa around 2.5 million BCE, making him a contemporary of some of Lucy’s descendants. Homo habilis was still much smaller than a modern man, but his brain was twice the size of a chimpanzee’s. He learned to hunt and to make crude stone tools by using one piece of flint to chip flakes off another. One of the great chicken-and-egg questions of human development is whether Homo habilis learned to make tools because he had a larger brain or whether the exercise of creating tools developed a larger brain. Chances are it will remain a mystery.

With Homo erectus, who lived around 1.5 million years ago, hominid life begins to look more familiar to us. Homo erectus probably had only rudimentary language ability, but he made more refined stone tools, most notably the hand ax; began to cook his food; established semipermanent camps; and perhaps formed long-term male-female bonds.

Homo erectus, like his fellow hominids, could raise a sharpened stick and bring down a small animal. But he was the first to go the next step and cook raw meat over an open flame. With the domestication of fire, Homo erectus changed everything for the Homo sapiens who came after, making the intentional use of fire the first Goldilocks moment in human evolution.

Today, sealed in our twenty-first-century man-made environments, it is hard to fathom the competition for survival that occupied our early human ancestors from sunup to sundown. It is even more difficult to imagine living without the benefit of millennia of human know-how, and without language, history, science—or fire.

BASED ON ANCIENT MYTHS and primitive art we can speculate that the earliest hominids learned the fine points of hunting by watching and imitating the actions of the nonhuman hunters with whom they shared the Great Rift Valley, and later, Eurasia and the Americas. Unlike the animal-teachers with whom they often competed for the same prey—rabbits, small cats, and warthogs—early humans had no sharp teeth or claws. To compete with other predators, our ancient relatives employed stone-tipped spears fashioned with their more dexterous limbs and fingers, and applied their superior problem-solving skills to outthink their prey and work in cooperation with other human hunters. With these assets in place, the prehistoric hunt was finally on.

EARLY HUMANS PROBABLY LEARNED to use naturally occurring fire before they learned how to create a spark with a flint stone, tending the embers to create their own fires. But fire under those conditions was a force of nature, both boon and bane. Things changed when Homo erectus learned to use flint stones to start their own fires. With fire at their call, if not completely under their control, humans could do more than cook their food, and share it around a hearth as a family or tribe. They could keep animals away at night, including the cave bears and giant wild cats that had previously made life in a cave exciting, if not impossible. They could bake clay to make a waterpot, an image of a fertility goddess, or bricks to build a shelter or even a temple. Fire was the tool that made other tools possible, from the first copper blade to the propulsion tanks for a communications satellite. Fire didn’t just shape tools; it may also have contributed to the evolutionary movement from Homo erectus to Homo sapiens sapiens.

Cooking meat doesn’t just make an animal taste better; it breaks down proteins, making the meat easier to chew and digest. With fire, humans no longer needed massive jaws to chew their raw food. Smaller jaws left room for a larger brain, taking hominids one step closer to modern humans.

OUT OF AFRICA

AFTER ABOUT ONE HUNDRED thousand years, bands of Homo erectus, now armed with fire to keep them warm and probably driven by increased population and competition for resources, began to travel farther from the warmth of the Great Rift Valley in search of food, eventually crossing the land bridge where Africa joins Asia. By about 400,000 BCE, small tribes of Homo erectus lived throughout Eurasia, reaching as far east as China.

When they arrived, they found they weren’t the only hominids on the planet.

Hominids in Africa and Eurasia took different evolutionary paths in the half million years after Homo erectus left Africa. When bands of Homo sapiens reached the Near East, they found that Europe and the Middle East were already populated by another bipedal, big-brained species, Homo neander-thalensis, popularly known as “Neanderthal man.”

Today, the word Neanderthal is often used as shorthand for an uncivilized or unintelligent brute. Cartoons show Neanderthals as hulks whose knuckles scrape the ground. It’s true that Neanderthals were stockily built, with heavy bones and signs of powerful muscle attachments that suggest they were extraordinarily strong by modern standards. Their faces looked more like those of Homo erectus than of modern humans, with a protruding jaw, a receding forehead, a weak chin, and a large nose. Nonetheless, Neanderthals walked upright, and their brains were larger than ours.

Comparing evidence from archaeological sites in Africa and Europe suggests that Homo sapiens and Neanderthal man were at a comparable cultural level when they met. They made similar stone tools. They hunted small, easy-to-kill animals. Though they created no art that we know of, you could argue that Neanderthals were one step closer to civilization than our ancestors, since they were the first hominids to bury their dead in a way that suggests ritual behavior.

Neanderthal man and Homo sapiens were close neighbors in the Middle East and Europe for about seventy thousand years; then the Neanderthals seem to disappear from the fossil record. For many years, the standard theory about their disappearance was that Neanderthal man was slowly pushed out of his habitats and into extinction by Homo sapiens, who was assumed to have been better adapted for the fight for survival. The latest science provides a more complex picture.

Beginning around 70,000 BCE—for Neanderthals and Homo sapiens alike–survival meant confronting a time of subfreezing temperatures and massive glaciers known as the Great Ice Age. It was not the first time ice had covered Earth. It might not be the last.

Born in fire, the earth is gradually cooling off. For roughly two million years, glaciers have expanded and contracted more than twenty times, at intervals of roughly a hundred thousand years. Brief periods of interglacial warming lasting about ten thousand years are followed by long periods of cold. (“Brief” is relative. The entire recorded history of mankind has occurred during the most recent warm spell.)

At the height of the Great Ice Age, around 20,000 BCE, glaciers covered one-third of the planet, including all of Greenland and much of Europe, northern Asia, and the Americas. As water froze, sea levels dropped hundreds of feet, exposing land bridges in the shallow waters of the Bering Strait, the English Channel, and the South China Sea. The temperature dropped to roughly minus 60 degrees Celsius (minus 74 degrees Fahrenheit). Glacial expansion seems to be caused by a combination of tiny changes in three different ways the earth moves: the tilt of the earth on its axis, the earth’s orbit around the sun, and the wobble of the earth on its axis (picture what happens when a top slows down).

Each of these movement patterns operates on a different cycle; each affects the relationship between the earth’s poles and the heat of the sun in a different way. The wobble, in particular, is erratic, affected by earthquakes, tidal waves, typhoons, and, ironically, the melting ice at the end of an ice age. Over time, the patterns interweave, pulling together and apart, sometimes increasing their effects, sometimes canceling them out.

Humans had evolved in the warmth of Africa’s Great Rift Valley in an interglacial period. They had grown accustomed to the harsher climate of the Middle East and Europe in the thirty thousand years since they moved out of Africa. But with the advent of the Ice Age, survival required much greater resourcefulness. It was a make-or-break moment in time.