Last Ape Standing: The Seven-Million-Year Story of How and Why We Survived (16 page)
Read Last Ape Standing: The Seven-Million-Year Story of How and Why We Survived Online
Authors: Chip Walter
Tags: #Science, #Non-Fiction, #History
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 fleshy 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.
There were no census takers fifty thousand years ago, so we don’t know how many humans were living on the planet, counting members of every species, though genetic studies may soon illuminate this; a few hundred thousand, perhaps, certainly less than a million. The generally accepted view is that we
Homo sapiens
bided our time in Africa until we launched a concerted worldwide migration beyond the Dark Continent beginning about this time. This is called, not surprisingly, the Out of Africa theory. According to this hypothesis
Homo sapiens
displaced and then eventually
re
placed all other human species that had arisen over the long epochs that preceded the post–African travels of
their
ancestors, whomever they might have been.
The Newest Members of the Human Family
As I was writing this book, various teams of scientists around the world announced the discovery of four entirely new species of humans, an indication of exactly how quickly the field, and the human family tree that reflects it, is changing. (See The Human Family Tree,
page 12
.) Three of these were discovered the old–fashioned way—fossilized bones stubbornly excavated from their hiding places in the ground. Of those three, two lived some time ago—
Australopithecus sediba
and
Ardipithecus kadabba
—species that roamed Africa two and four and a half million years ago, respectively. From these remains paleoanthropologists have been able to develop some fairly deep insights into these creatures’ anatomies and lifestyles.
Based on four partial skeletons found in South Africa,
sediba
illustrated an emerging theme in paleoanthropology: there was a good deal more variation in ancestral humans than previously thought, and therefore lots of room to debate where they fall in the family tree.
Sediba
seems to have combined some old australopithecine traits and some traits of early
Homo
species. Its brain wasn’t terribly large (about 450 cc), but hand, pelvis, and leg bones indicate it may have been an early tool user and well on the way to walking upright more often than not. Yet fossilized plants found with some specimens tell scientists that sediba lived in forested areas as well as open ones and often ate fruits like their chimpanzee cousins.
Researchers read these clues in different ways. Some argue that
sediba
was a precursor to the
Homo
species of humans that followed. Others didn’t believe this was possible because that branch had already sprouted on the human family tree a half million years earlier with the emergence of
Homo rudolfensis
.
Ardipithecus kadabba
is an ancestral human, and lived as many as three and a half million years before
sediba
in Ethiopia. (Some debate this age and set it one million seven hundred thousand years earlier.) He is ancient enough that his big toe was still designed for grasping tree branches, though other aspects of his anatomy indicate he moved on two feet on open ground. His brain was about the size of a modern bonobo at 300 to 350 cc, but his smaller incisors indicate, at least to some paleoanthropologists, that he and his
fellow creatures were more socially cooperative than chimps. Male chimps have large incisors often used when battling for the attentions of the troop’s females. This makes sense if he was spending more time in the more dangerous open grasslands where he would have to rely more on others in the troop for survival.
The third and fourth species come from a different time and different parts of the world than the first two. Both dramatically reinforce the emerging reality that our direct ancestors coexisted with a variety of other extremely sophisticated humans throughout the world until very recently. Just a few years ago an assertion of this kind would have been considered heresy in the field of human evolution. Each of these species lived when we
Homo sapiens
did, and DNA evidence indicates that at least one also mated with us, and with Neanderthals. Human species embraced one another, it seems, in more than a metaphorical way when they had the chance.
Of these two the most recent discovery was announced in March of 2012, and because of its novelty remains controversial. The fossils haven’t even yet acquired a scientific classification. Instead researchers call their find the Red Deer Cave people, humans, but not likely
Homo sapiens
, that lived in south central China, north of Vietnam, as recently as 11,500 years ago. That these people were setting up camp not long before
Homo sapiens
had made their shattering transition from hunting and gathering to agriculture is one of the aspects of this discovery that has anthropologists both giddy and astounded.
The astonishment, however, only begins there. The fossils reveal that these people looked a little bit like us but also like more ancient humans. They have our rounded brain cases, less sloped than Neanderthals, but still retained thick, simian–style brow ridges. Like ours their faces were flat and tucked under their brain, but their chin, though the jaw juts forward, isn’t squared off like ours. And strangest of all, scans of their brain cases indicate that they had modern frontal lobes, but archaic parietal lobes, which sit farther back in our brain. It makes one wonder if their reality was different from ours, and if it was, how?
So where did these remarkable people come from? Scientists have speculated along three lines: They might have been descended from a group of
Homo sapiens
that departed Africa earlier than generally thought and survived and evolved in isolation. They may
truly be an entirely different human species, like Neanderthals, people who evolved from an earlier branch of the human family tree,
Homo heidelbergensis
or
Homo erectus
, perhaps. Or they could be hybrids:
Homo sapiens
that mated with archaic humans who were also living in south China, something that might help explain their unusual mix of features.
The fourth and perhaps the most intriguing species recently discovered left behind almost no evidence of its existence; no clues about how it looked, what tools it used, or where it came from; hardly even a bone. Like the Red Deer Cave people it has also not yet been assigned a scientific name. Instead researchers refer to this species as the Denisovans because the two tiny fossils they
did
leave behind—a wisdom tooth and the tip of a pinkie finger—were found in Denisova Cave in the remote Altai Mountains of Siberia. You could hardly imagine more meager leavings. Yet, after scanning the mitochondrial DNA within these tiny specimens, scientists at the Max Planck Institute for Evolutionary Anthropology managed to decode the creature’s entire genome. And when they had they realized that the juvenile to whom these paltry fossils had once belonged represented an entirely new human species that had hunted and settled in these mountains forty thousand years ago. Amazingly, Neanderthals,
Homo sapiens
, and Denisovans each lived in the very same cave, though probably not at the same time. The DNA analysis also revealed that the peoples who became
Homo sapiens
, Neanderthals, and Denisovans all shared a common ancestor a million years earlier. It’s not yet known exactly which species that was, possibly
Homo ergaster
.
It turns out that we share a genetic link with Denisovans in another remarkable way. In analyzing Denisovan DNA the scientific team compared it with living humans from six groups: the !Kung people of South Africa, Nigerians, the French, Papua New Guineans, Pacific Bougainville Islanders, and the Han Chinese. They were electrified when they found that between 4 percent and 6 percent of the genomes of the people of Papua New Guinea and Bougainville Island contain Denisovan DNA. Scientists surmise the genes were introduced to the islands when the hybrid descendants of
Homo sapiens
and Denisovans migrated into Southeast Asia and later Melanesia. There is even some evidence that these descendants made their way to Australia and the Philippines.
It’s difficult to not be transfixed by these discoveries when you really take the time to think about it. Like Neanderthals and
Homo floresiensis
they are species who fought and struggled and lived sophisticated lives for tens, even hundreds of thousands of years alongside our direct ancestors on the same planet we inhabit today. And if that isn’t astounding enough, some even mated with our kind, contributing forever to our DNA. Were these aberrations or the norm? How many more species and hybrids might we find now that DNA analysis has opened so many genetic doors?
If that’s true (and there’s little debate that it is, though it’s becoming clear it wasn’t quite this simple), most of the different varieties of humans, given their nomadic ways, must have crossed paths from time to time as they wandered into the edges of one another’s territories.
There is evidence of this in the rocky hills of Galilee, not far from Nazareth, the birthplace of Jesus Christ. In 1929, in caves that pock the hills of Qafzeh, Israel, two scientists found an ancient burial ground and, remarkably, the bodies of eleven anatomically modern humans. At first scientists thought the bones were no more than fifty thousand years old, but later, improved dating technology revealed that they were nearly twice that age, making them the oldest modern human fossils to be found outside Africa. As researchers continued rummaging through the site, they realized the bodies retained some of the more archaic features of their ancestors, but that they were culturally advanced. The ornamental shells and red, yellow, and black ocher paints they left behind indicated as much. So did the hearth and the burials of the bodies themselves, one of which included a mother and her child. Their tools, however, weren’t as advanced as later
Homo sapiens
’.
