by Chip Walter
Mitochondrial genetic studies tell us that around this time one small group of modern humans living in Ethiopia or the Sudan, armed with an assortment of high–tech tools—bone and ivory hand axes, long spears, and fire–hardened stone knives mostly—headed northeast, then over the Red Sea into Yemen on the Arabian Peninsula.
Undoubtedly, being human and curious, several waves of our direct ancestors ventured from their mother continent into the Mideast during this time. Modern human migration wasn’t likely one solitary foray northward. During cold oscillations, seas everywhere would have grown shallower, including the Red Sea and the Gulf of Aden. Right where these meet at a place with the dramatic name the Gate of Grief (Bab el Mandeb), the continents of Asia and Africa nearly kiss. Even today the distance between them is slender: no more than twenty miles of seawater divides the huge continents. But during frigid climatic swings the Red Sea sometimes dropped more than 210 feet, narrowing the straits by several more miles, nearly attaching Africa and Asia like two continent–size Siamese twins.
Though there is no evidence the seaway ever completely dried out, climatologists believe that a chain of small islands sometimes emerged between the immense landmasses. The shorelines of those islands would have made excellent places to fish and eat before moving northeast to the next island. In time, the traveling tribes inevitably made their way, perhaps in small boats or on rafts, island by island, to the underbelly of Asia.
This feat, however long it ultimately took, liberated our kind from the boundaries of Africa to head off to every continent and landmass the planet had to offer. We weren’t the first to find a way to Asia, but this migration, or series of them, would, in the astonishingly short space of fifty thousand years, utterly revamp an entire planet.
Once on the mainland of Asia, modern humans began to ripple outward. Some bent east, hugging the shorelines of Yemen, Oman, Iran, and Pakistan as they headed toward India, and others migrated north through Mesopotamia (Iraq). There, this second group split again, some working their way from Turkey through the Danube corridor, others sticking closer to the Mediterranean coast as they headed toward Greece and the boot of Italy.
The splitting branches of humans grew like a bush. The fossil and genetic evidence tells us that within five millennia our kind had settled the ancient continents of Sunda and Sahul, landmasses that exist today as the oceanbound islands of Indonesia and New Guinea and the continent of Australia. Forty–five thousand years ago, however, the Indian Ocean was shallower, and these exposed shelves of land were separated by straits no more than sixty miles at their widest. This means that inside of ten thousand years, wandering Homo sapiens doggedly walked from the eastern Sahara to the plateaus and mountains of western Australia.
Meanwhile, other branches of our kind that had radiated into Mesopotamia and moved west spent the next fifteen thousand years settling much of Europe, as far away as Spain and well north of the Alps. Still others expanded north and east into Asia, across the highlands of Tibet and the steppes of Russia until they had nearly reached the top of the world to cross the land bridge between Russia and Alaska. From there they made for Canada, into North America and then southeast to the Meadowcroft settlement just outside Pittsburgh, Pennsylvania, sixteen thousand years ago, and finally into Central and South America to become, someday, the Incans, Mayans, Aztecs, Hopis, and scores of others. The settlers of Meadowcroft predated European explorers by a mere 155 centuries.
The upshot of all of this restless meandering was that after millions of years of evolution, in the tiny space of fifty millennia, the newest addition to the human family tree had wandered into and settled two Americas, all of Europe, Asia, Africa, Southeast Asia, even Japan. Only Micronesia and remote islands scattered across the Pacific, places such as Tahiti, the Philippines, and Hawaii, remained uninhabited. It took another two thousand years, as civilizations in Egypt, Mesopotamia, China, and India were rising, for small groups of dauntless explorers to travel across thousands of miles of open sea to populate, for reasons we have yet to fathom, those tiny specs of land.
Though the time scales we are talking about—mere tens of thousands of years, rather than hundreds of thousands or millions—seem relatively short, they still dwarf the length of recorded human history. Civilizations in India, China, and Egypt have come and gone within thousands of years. Alexander’s empire disappeared within a few generations. Even Rome ruled most of Europe, parts of the Middle East, and North Africa for fewer than one thousand years. Ninety–five percent of the time that our particular brand of humanity has existed remains mysterious and almost entirely unrecorded. Nevertheless a great deal happened and a great deal of territory was covered.
Despite the mountains of research (and years of heated debate) that focus on the departure from Africa of our species, it’s important to remember that we were not the first humans to forsake the continent for other parts of the planet. But before we get too deeply into the specific and considerable wandering of earlier humans, it might be best to clarify some recent, and surprising, rearrangements of our family tree.
For decades paleoanthropologists generally agreed that Homo erectus was a single species from which we evolved directly, and creatures we now know as Homo ergaster were assigned to the erectus line. But it now seems, at least by the lights of an increasing number of researchers, that ergaster represents a species of its own, and the primates we have been calling erectus are actually a potpourri of many human species whose bones simply haven’t turned up in great enough numbers to warrant their own names or branch on the family tree. Now paleoanthropological sentiment now seems to be leaning toward our being descended, a few species removed, from ergaster, while erectus, and other humans who left Africa and wandered east, became one or several other species that eventually died out.
Whether or not we are descended directly from them, the species we collectively refer to as Homo erectus rose up and began to fan out to the mid and far east in small, tight brigades as long ago as 1.9 million years. Very adventurous to place some temporal perspective on this, consider that this is one million seven hundred thousand years before we Homo sapiens even showed our face. Or put another way, eight hundred times the twenty centuries that have passed since Augustus Caesar ruled the Roman Empire. Homo erectus, and the cousin species they left behind in Africa, were wickedly smart for their time and armed with the greatest evolutionary advancements of their day. Not bigger fangs, shaper claws, or stronger bodies, but a knack for thinking on their feet, working together, and adapting on the fly.
As a group they were tall, slim hipped, and built for long–distance running in the unforgiving sun of the equatorial lands where they arose. Their elongated limbs exposed the maximum amount of body surface to the air to help keep them cool. They were probably nearly hairless by this time, able to perspire much the way we do (chimpanzees have about half the sweat glands we do, mostly on their hands and feet, which aren’t covered with hair), and outfitted with a complex network of blood vessels in their rather large heads, which helped efficiently vent heat and thereby avoid death by heatstroke. They were more adept toolmakers than Homo habilis before them and carried, by all accounts, an entirely new kind of technology with them everywhere, the same way today we tote around cell phones—the Acheulean hand ax, which was something like a Neolithic Swiss Army knife. Soon they would tame fire.
Before long, wave after wave of Homo erectus were settling parts of Arabia, China, India, even Indonesia, though they apparently never made it as far as Australia. Perhaps they weren’t quite gifted enough to develop the advanced seafaring skills they needed to make it that far, or maybe the erratic climate prevented them. Or perhaps many tried, but none succeeded, or maybe they did succeed but their remains have yet to be found. Whatever the case, they wandered and meandered and migrated hither and yon with a far less sophisticated toolkit than Homo sapiens did when they exited Africa 1.7 million years later. But migrate they did.
One branch of the Homo habilis family (o
r perhaps an early version of Homo erectus) managed to travel all the way to Dmanisi in the Republic of Georgia 1.78 million years ago. Once again the weather helped. Between 1.9 and 1.7 million years ago Earth’s climate was enjoying a respite between glacial periods, and these humans might have made their way up what would have then been a lush Nile River valley and then east across the narrow straits of Suez to the Arabian Peninsula before heading north of the Black Sea. Another branch apparently walked through a “green Sahara” filled with tall grass, brimming with wildlife, then made their way to current–day Algeria to settle at a site called Aïn Hanech.
Something more than simply human wandering was afoot here. The lands where these creatures were settling not only stretched from Indonesia to North Africa, but represented a widening variety of environments. They ran the gamut from marshes and streams to seacoasts and wooded mountainsides. The creatures were not only putting more distance between themselves and their home continent, but between themselves and the dictates of their genes. They were using their brains and creativity to adapt. While the other great apes had for millions of years been retreating to increasingly smaller forests, sticking to familiar environments where they were comfortable and for which they were genetically suited, these ancient humans, armed with their tools, clothing, and that magical thing called fire, were adapting their new environments to them, not the other way around.
By a million to 1.3 million years ago, entirely new species began advancing into the cold climates of Europe, trudging as far north as the British Isles, from (scientists suspect) northwest Africa across the Straits of Gibraltar. These were a species paleoanthropologists call Homo antecessor, a toolmaking cave dweller with a brain three quarters the size of ours and a more human and less simian face whose remains were first discovered at a railroad cut in Sierra de Atapureca, Spain. Another species descended from antecessor known as Homo heidelbergensis may also have made his way to this same area. More on him soon. But in either case each represented newly minted humans, most likely descended from Homo ergaster.
Interesting evolutionary events had been unfolding on the plains of Africa for the past several hundred thousand years, making the story of our own emergence both more interesting and more murky. While brigades of various hominin explorers were fanning off in every possible direction, the root species (including ergaster and erectus) were continuing to diversify back on the home continent as well. Around seven hundred thousand years ago, an altogether new, and crucially important, creature called Homo heidelbergensis stepped out of the mists of time.
The remarkable thing about heidelbergensis, so named because the first specimen was found near Heidelberg, Germany, is that it is the species from which both we and Neanderthals descended. That news has utterly rearranged the human family tree. Until recently it was thought that we could not possibly share anything much, especially our ancestry, with these tough, burly creatures who passed into extinction some twenty-five thousand years ago. We were, according to common wisdom, directly descended from Homo erectus. Yet, it turns out, if not for heidelbergensis, neither we nor Neanderthals would ever have walked the earth.
The creatures, the people, who later evolved into Homo sapiens and Neanderthals began to part ways, genetically speaking, from heidelbergensis almost as soon as heidelbergensis itself emerged. Some members of the species remained on Africa’s horn (and are sometimes referred to as Homo rhodesiensis), but others, with a more extreme case of wanderlust, moved northwest across a new green Sahara to Gibraltar and then into Europe, following in the footsteps of Homo antecessor.
The archaeological evidence suggests that these nomads became the first humans to build shelters, probably of rock and wood, and hunted big game, like Irish elk, mammoths, and European lions, with long wooden spears. These inventions served them well in the colder climates they were dealing with throughout Europe, especially when glacial ice descended. They had large brains—1100 to 1400 cc, as large as ours—and by this time were easily the brightest of the planet’s primates. Even more than antecessor, the shape of the outer and inner ears of these people indicates that they could make fine differentiations between sounds, a trait that leads some scientists to speculate they used sophisticated speech of some kind. Dental wear on teeth in the right side of their mouths means they may have been using their mouths as a “third hand” clenching tough food, tools, or clothing on their right as they worked on them. This could mean they were right–handed, and right–handedness is associated with language and lateralization of the brain.5 Thin soup as scientific theories go, but something worth chewing on.
The original heidelbergensis was, it seems, thick boned, huskier and stronger than erectus, who was taller and slimmer. Not that at six feet he was short, but with a frame that easily supported two hundred or more pounds, he was built like a bouncer, or college fullback, a trait that mystifies scientists somewhat since most African primates tended to be long of limb, the better to expose more of their body to the air, a form of natural air–conditioning.
Homo heidelbergensis
The European branch of heidelbergensis maintained and built upon these traits as they evolved into Neanderthals. The colder climate favored thicker, stockier creatures that exposed less of their bodies to the air. (Inuit people and the native residents of Siberia also show these same traits as ways to conserve heat.) The strength and endurance these bodies were apparently blessed with were certainly assets as they dealt with a punishing climate. Bulkier, stronger, physically tougher individuals would also have been favored when it came to hunting big game. As far as we know, these people and the Neanderthals that followed them did not throw their wooden spears when they hunted. Instead they used them to repeatedly jab their prey at close range, a dangerous way to shop for dinner.
You can imagine that this not only took courage and strength, but a body that could survive being tossed around by a wounded and enraged lion, mammoth, or woolly rhinoceros and still bounce back. Paleoanthropologists have found evidence all over the world of the beatings Neanderthals withstood. Skeletons found from the Middle East to Western Europe have revealed ugly injuries to their ribs, spine, lower and upper legs, and skull. What’s more, these injuries usually healed and there are no signs of infection. More than once scientists have noted the injuries resemble the kinds of hammerings that rodeo riders sustain from big, bucking animals. Except in the case of Neanderthals they weren’t riding bulls or horses, they were hopping on the backs of wolly rhinos, aurochs, or elk to jam their long spears in one killing blow through their back behind their necks. From time to time, of course, the animals they hunted might not have taken kindly to this.
Despite the beatings Neanderthals survived over the next half million years and spread throughout Europe, following the retreating glaciers north when temperatures moderated, and heading south when the glaciers returned. In time they became the dominant primates in Europe and settled it from the British Isles to the shores of the Black Sea.6
For the African branch of the family, life was challenging, too, but for entirely different reasons. Continuing increases in climate fluctuation meant surviving waves of crippling droughts. But their large brains, their tough bodies, and their increasingly strong social structure saw them through. In the end, both the Africa and European branches of humanity outlasted several climatic swings, until finally, around two hundred thousand years ago, they had completed their transformation into two entirely different, but enviably advanced, species—the first Homo sapiens and the first Neanderthals.
If you hold the fossilized skull of a Neanderthal in your hand and closely inspect it, you might find it difficult to believe we share a common ancestor, but time, climate, and random chance are powerful change agents. Their brow ridge is thick, their heads longer, shaped more like a watermelon than a cantaloupe, like ours. Their chins recessed, or more accurately the middle part of their face protruded more than yours and mine and looked more muzzlelike around the mouth and nose, which was large and flesh
y and well rigged for warming the cold northern air they breathed. And they were stouter, bulkier, barrel–chested.
We were slimmer than they were, but not so much because Homo sapiens in Africa had grown more gracile over time; we simply didn’t accentuate the robust traits we had inherited from heidelbergensis the way Neanderthals did. In fact, when the two species later met in Europe six hundred thousand years or so after the original heidelbergensis branches split, Homo sapiens were probably on average taller, if not stronger, than their Neanderthal cousins.
Climate made Neanderthals even huskier than their big–bodied ancestors. While their collarbones were long, their broad shoulders curved inward around a chest that was both broad and deep as if to better husband their body heat. Their fingers, which must have nearly always been exposed to the cold, grew stubbier and rounded at the tips, an antidote to frostbite. Their big upper bodies balanced on a pair of bowed thighs above Brobdingnagian knees and shortened shins. But this did not mean they walked hunched over, apelike. They didn’t. Like us they stood fully upright and could walk and run just as well as we do. They were simply a human species optimized for the cold, remarkably strong and outrageously intelligent. And given their longevity, astute and wise in the unforgiving ways of survival.
By the time we and Neanderthals had emerged, at least four (and probably more) intelligent, self–aware human species were still living on planet Earth. (See sidebar “The Newest Members of the Human Family,” page 90.) Each was colonizing settlements spread sparsely from Britain to Indonesia, and from the Balkans to the southern tip of Africa. We do know that Homo antecessor and heidelbergensis, and their precursors ergaster and habilis, had by now gone the way of the dinosaur, but erectus, or some version of it, still roamed Asia while Homo sapiens made its itinerant way around Africa, and Neanderthals ruled Europe and west Asia.