Our direct ancestors left Africa around sixty thousand years ago and, after taking thousands of years to reach Europe, coexisted with the Neanderthals there, until the latter died out twenty-eight thousand years ago. The Neanderthal extinction is generally attributed to either too much competition (clever, aggressive Homo sapiens outmaneuvered them) or too much loving (we interbred with them and eventually swamped their genome with our far larger population).1 It’s also been suggested that in the same way that Western Europeans caused the decimation of indigenous populations when they made first contact in the last few centuries, Homo sapiens may have brought new diseases into the Neanderthal world and thus contributed to their decline. Most recently, Paul Mellars, a University of Cambridge archaeologist, and colleagues found evidence that a sudden climate shift, when the temperature dropped as much as 8°C, precipitated the demise of the species.
As the perceived mental gap between humans and animals has narrowed, so it has for modern Homo sapiens and their recent ancestors. For a long time Neanderthals were considered brutish, unintelligent creatures with no language or symbol use. But as the anthropological evidence has accumulated, they have undergone something of an image upgrade. It’s become clear in recent years that even though Neanderthals didn’t have as rich a culture as we did, what they eventually developed before they went extinct was fairly sophisticated. It’s worth keeping in mind that although the Neanderthals disappeared soon after humans arrived, our species has yet to prove that it has even half the longevity outside of Africa that they did.
Another cousin, thought to have descended from Homo ergaster, was discovered only in 2003. The scientific world was shocked by the news that on the island of Flores in Indonesia a team of scientists had unearthed the remains of a creature they called Homo floresiensis. Prior to this no one had suspected that humans had once had relatives as closely related as Neanderthals. Nicknamed the hobbit, H. floresiensis is an interesting contrast to the Neanderthal. While the northern branch of the family was large, thickset, and reputed to have had larger brains than ours, the hobbits were mini-hominids, reaching only a meter’s height at adulthood. The remains of seven different H. floresiensis individuals were found; they died between 95,000 and 13,000 years ago. Flint blades were discovered alongside the remains, indicating that the hobbits were also tool users. Scientists say the H. floresiensis tools are stylistically similar to a cache of 800,000-year-old Homo ergaster tools that had been found nearby, suggesting they inherited the technique from their H. ergaster ancestors.2 The last of the hobbits disappeared at the same time that a nearby volcano erupted, so it’s believed that this catastrophe led to the species’ extinction. The individual that died 13,000 years ago was our last, closest cousin.3
Homo sapiens emerged as a single small population around 200,000 years ago in Africa, and while there are no examples of nonfunctional symbol use of any kind before this time, sparse but clear examples begin to appear from this point on. In 2003 the skulls of two adults and a child who probably lived about 165,000 years ago were found in Herto, Ethiopia. These humans resemble us in many ways, with only minor differences: they were somewhat larger overall and had a slightly protruding browridge. Most interestingly, their skulls had been flayed and ritually incised after death. It’s possible the practice is related to the rites of some modern-day groups that worship their ancestors in this way.
Altogether, archaeological and paleoanthropological evidence suggests that Homo sapiens remained relatively stable for around a hundred thousand years. Then, between sixty thousand and eighty thousand years ago, there was a dramatic expansion of certain genetic lineages in the African population. At the same time there was a striking change in technology and culture. Homo sapiens do not appear to have changed physically during this period, yet they began to produce many more types of unambiguous symbols. New forms of tools such as those for scraping skin and shaping bone and wood appeared, and novel techniques for flaking stone to make tools can be deduced. Some anthropologists believe that at least some of the sharpened stone and bone tools created at this time could actually have been the tips of arrows, indicating the invention of archery and presumably the ability to access more and better food. In addition, many traces of art, such as perforated shells for jewelry and other kinds of decoration, have been found. The oldest known examples of human art—two pieces of ocher with a hatching design clearly carved into them—were created seventy-seven thousand years ago and recently recovered in South Africa’s Blombos Cave. It appears that humans were also engaging in some kind of trade at the time. The shells, for instance, had been clearly transported from other locations to the sites where they were ultimately found.
Some small groups of H. sapiens left Africa and settled in places like Israel a hundred thousand years ago, but all of these colonies eventually died out. Our direct fathers and mothers left Africa only sixty thousand years ago, soon after their cultural and technological shift, and they successfully introduced their new way of living everywhere they established a foothold. Everyone alive today descended from this small band of travelers.
A number of possible routes have been suggested for this African exodus. The first modern humans may have departed via North Africa and then split, some going west to Europe and the rest heading east to Asia. The other likely route out of Africa was via Ethiopia and was essentially a coastal route through southern Asia all the way to Australia. This group colonized Europe from western Asia, some fifty to forty thousand years ago.4 (It’s possible that these humans bred with the relatives who’d left earlier, around the 100,000-year mark—or that the initial small groups of colonists simply died out, taking their slightly older genome with them.) Paul Mellars notes that if this coastal route was the first successful exit from Africa, then rising sea levels since then mean that most traces of this journey now lie under as much as one hundred meters of water.5
Much is made of the brain’s plasticity, but the recent, rapid spread of H. sapiens across the globe powerfully illustrates how plastic the body is over generational time. Wherever a trail was blazed and settlers were left behind along the way, the human form shrank or expanded or somehow changed to accommodate whatever harsh environment it found itself in. When we left Africa, we were tall, in contrast to the Chukchi, who live inside the Arctic Circle and who descend from the pioneers of that first exodus. The geneticist Spencer Wells has been rebuilding the recent history of humanity by tracking the Y chromosome across the world and back in time up to sixty thousand years. He visited the Chukchi, and noted that even though the nighttime temperature in their homeland can fall as low as–70°C, the people have adapted in many ways. In addition to cultural innovations that enable them to live somewhere so cold, they have changed physically as well. Now they are squat and short-limbed, useful adaptations to the extreme cold in which they live.
As humans spread across the globe, their material and symbolic culture grew richer. By the forty-thousand-year mark, Homo sapiens were sculpting from stone, painting in caves, and creating a greater variety of musical instruments and jewelry. They were also ritually burying their dead with grave goods, suggesting that they could imagine a place after death where those items might be useful.
After settlers arrived in Europe forty thousand years ago, it took some thirty thousand years to invent agriculture, and in the ten thousand years that followed (bringing us to the present), agricultural techniques have radiated out across the world. In the last five thousand years we’ve experimented with architecture, raising edifices that range from the ancient pyramids to the Empire State Building, and in the last three hundred years industrial technology has replaced human labor in countless domains. To be outfitted with a handful of electronic devices is just another day in the life for most Westerners. For modern humans, unlike the Neanderthals or any other species on the planet, culture begets more culture. In the last fifty thousand years, until the present moment, the innovation and replacement of material artifacts have not just accumulated but
continually accelerated.
From Toumai through Lucy and the Herto Homo sapiens of 165,000 years ago to the small band of humans that left Africa some 60,000 years ago, there are two main theories about the way in which language changed and was elaborated in this bushy, branching, complicated family. As with most evolutionary tales, some scholars see sudden dramatic change from which everything flows, while others are more inclined to detect subtle gradations and tentative steps.
The big genetic bang scenario for culture is most often associated with the archaeologist Richard Klein. In this view, a sudden alteration in the organization of our brains, probably resulting from a genetic mutation, occurred around fifty thousand years ago. This change was the author of all the cultural innovations that followed, as well as the final successful journey from Africa that left humanity spread across the globe. The saltation gave rise to modern language, words and syntax being the cause and the means by which cultural and technological change spread and evolved. Proponents of this theory tend not to consider the cognitive and potentially linguistic capacities of humans from fifty thousand years ago within the larger context of prehuman skills. The implication is more that an all—language and culture—sprang from a nothing.
If all the significant developments as far as symbol use is concerned took place around fifty thousand years ago, then Neanderthals could not have had symbolic culture. Proponents of this view explain that the evidence of Neanderthals burying their dead, and in at least some cases doing so with grave goods, is accidental. (They only did so to keep the corpses from being eaten by scavengers, and the grave goods were merely swept into the graves by accident.) Examples of the complicated Neanderthal stone tools and jewelry that appeared around forty thousand years ago are generally explained as borrowings from Homo sapiens after exposure to their culture and ideas.
Even if you don’t subscribe to the notion that a dramatically demarcated revolution occurred, it’s clear that a major shift in the history of the human mind was taking place. The most compelling evidence for this “great leap forward” is the proliferation of cultural artifacts that have been discovered from this period. Indeed, symbolic and technological artifacts are often cited as evidence that language existed at some point in the past, but the fact that the largest number of early symbolic artifacts cluster around the fifty-thousand-year mark doesn’t mean that humans weren’t symbol users before then. As scholars like Terrence Deacon point out, the absence of evidence is not evidence of absence. Deacon cites the case of African Pygmy societies, which leave little more than bone and stone artifacts as traces of their existence, even though their language, cultural traditions, and music are as complicated as those of any iPod-toting modern person.
Deacon takes the contrasting view that symbol use probably began around the two-million-year mark, when our ancestors became bipedal—thus freeing up their hands for tool manufacture and for gesture—and their brains expanded significantly. With that expansion came reorganization of the brain as well, and this, argues Deacon, is a more direct proof of the capacity for symbolic communication than what the archaeological record reveals. (See chapter 14.) Thus symbolic language has been accruing from around the time that the australopithecines were replaced by the hominids, and in the last fifty thousand years it became transformed into its modern incarnation.
Similarly, in the more gradualist view described by the archaeologist Paul Mellars, the traces of art and culture that begin to accumulate in the last 200,000 years are a gradual elaboration of new mental abilities under different pressures (such as dramatic weather changes, and population and social pressures). These pressures did not result from spectacularly anomalous situations, according to Mellars, but were more or less like those that affected later, established agricultural communities.
It’s more plausible in this view that Neanderthals did have an indigenous symbolic culture. (How could they not have if their distant ancestors already had the beginnings of one?) At any rate, even if their cultural and technological innovations were borrowings from modern humans, the loans indicate a clear capacity for complex symbol use, if not the inclination to invent it. No other species has borrowed elements of human culture in this way.
Whether symbol use began with hominids or with the australopithecines, it is hard to imagine, given all the language foundations that came together before the 6-million-year split from chimpanzees, that nothing relevant to the development of language took place in the course of the next 5.95 million years, after which modern language suddenly burst forth. Still, we won’t know the details until we invent some better methods of answering this question, and until the archaeological record becomes richer. Thanks to some very recent genetic detective work, the period from 200,000 years ago until the present has unexpectedly become much clearer. The most telling finding was announced in 2002—at some point in the last 200,000 years the FOXP2 gene, which has so much to do with vocal communication and learning, changed in humans, and this change was advantageous.
The fossil record, and the ingenuity of the men and women who read it, have yielded many rich stories about the history of the earth and life on it. But the record is shaped by arbitrary forces—when someone perished, and the environment in which they did so (which determines whether their remains become preserved) are all a matter of chance, and the odds against any kind of preservation and fossilization are galactic. In contrast, genetic detective work uses data from modern populations. So when that information is combined with findings from paleoanthropology, archaeology, and psychology, the door of time is thrown wide open.
The most familiar nugget of contemporary genetic knowledge is that we share many genes with other animals. We now know that only a very small number of genes in our genome are specifically human, and we know that genes we share can have mutations that are distinctly human. It is finally clear that genes build individual organisms in really complex ways, but what has happened to our genes through time—before and after the six-million-year mark?
Genomics and population genetics, combined with other traditional sciences, have turned up some decidedly odd findings about gene history. It’s thought, for example, that the genomes of humans and other vertebrates contain bacterial genes that were once visited upon their hosts as infections, literally embedding themselves in the genome and permanently altering the genetic building blocks of the host species.6 Moreover, it was recently announced that a number of living individual humans actually have more genes than others. At least for some of us, the human genome has accumulated genes in generational time. More genes than normal may cause disease, or they may have no effect at all. We know also that some features can devolve as well as evolve. Under certain conditions, flies can be induced to revert to an ancestral state.7 In the history of their species, wingless stick insects have evolved wings and lost them four separate times. Body hair, according to Richard Dawkins, is one of those traits that may recede or reappear a number of times in the history of a species, as was the case with the mammoths, which rapidly became woolly when the most recent ice ages hit Eurasia.8 The same is true of the jutting brow of our hominid ancestors. It’s one of the features, Dawkins writes, that “hominids seem able to acquire and lose again at the drop of an evolutionary hat.”9
The primary cause of these changes is genetic mutation. Genes mutate simply as a matter of course, and generally as an artifact of the process of replication. A genetic mutation can have a positive or negative effect on the organism in which it occurs; it can cause a disease (carriers of two copies of the gene that causes sickle hemoglobin cells will be afflicted by sickle-cell anemia), or it can confer greater resistance to disease (carriers of one copy of the sickle-cell gene have greater resistance to malaria), or it can end life.
One of the ways that genetic change spreads through a group of animals is called genetic drift. With drift, mutations that are neither positive nor negative for the individual carrier (in terms of affecting one’s ability to produce more offspring) get passed o
n through the generations. The random drift of negligible genetic changes can eventually spread a mutation through an entire population so that everyone has it. Or a mutation may disappear altogether as its carriers eventually die out.
The other force that affects how a new version of a gene fares and how widely it is passed on is selection. Negative selection removes deleterious genetic variants. In contrast, if a genetic mutation results in a trait that helps its carrier have more offspring (compared with individuals who do not have that genetic mutation), it will spread through a population much more quickly than the casual infiltration of mutations by genetic drift. This is positive selection.
Back in 1990, when Steven Pinker and Paul Bloom championed the investigation of language evolution, they proposed a scenario that could explain the natural selection of language. They based their hypothesis on knowledge from fields like anthropology and psychology, as well as logic, arguing that the complicated design of language, as with the eye, could not have arisen without selection. Recall that they presented this argument in the face of the ubiquitous criticism that because we can never really know if a trait was directly selected or if it arose by accident, let alone why it was selected, throwing out theories to explain adaptation is just an exercise in fiction.
The First Word: The Search for the Origins of Language Page 25