Masters of the Planet

by Ian Tattersall

  The only evident alternative is that our strange intellectual faculty is attributable to a novel neural conformation, a change in the internal organization and wiring of our brains. Acquisition of such a novelty would not in itself be unprecedented; after all, the human brain has a long and largely accretionary history going right back to the earliest vertebrate brains half a billion years ago—and beyond. Nothing inherently new there. But the results of this acquisition were revolutionary: in today’s jargon, they were “emergent,” whereby an adventitious change or addition to a pre-existing structure led to a whole new level of complexity in function.

  Exactly when our amazing capability was initially acquired is something we cannot read directly from the fossil record: the paleoneurologists, those specialists who specialize in the form of fossil brains as determined from the impressions they leave inside the cranial vault, cannot even agree in principle if there is any functional significance to the minor external shape differences we see between modern human and Neanderthal brains. All we know for sure, from the archaeological evidence, is that the two species behaved differently. The Neanderthals seem to have possessed a sophisticated version of the “old-style” hominid way of dealing with stimuli, using purely intuitive processes. In contrast, we symbolic Homo sapiens are processing information in an entirely revolutionary and unprecedented way, even though the “old” brain is still very much there, deep inside.

  GENES, LANGUAGE, AND LARYNXES

  I mentioned briefly that some believe our new way of doing business is due to the very recent acquisition of a “symbolic” gene. Excitement about this possibility ran high after scientists discovered that the human version of a gene called FOXP2 was intimately involved in our language abilities, at least to the extent that people possessing a mutated form are unable to speak properly (though they don’t seem to be more broadly cognitively impaired). Imaging studies showed that such people have reduced activity in Broca’s area of the brain. The excitement increased yet further when various Neanderthals were shown to have possessed the normal human version of the FOXP2 gene, sparking speculation that here was proof that the Neanderthals had possessed language. If this speculation had been on the mark, it would have been huge in its implications for complex consciousness; for language is a supremely symbolic system that depends on the creation and manipulation of mental symbols for its very existence. Any organism able to generate language would almost certainly have been capable of exhibiting all of the other correlates of symbolic thought. But if only it were that simple: it turns out that numerous genes (all of them working as they should) are involved in determining normal language and speech production in humans. Indeed, so many genes are intimately choreographed in the developmental process that sometimes it seems a miracle that any of us ever develops normally. In view of all this it is evident that the notion of a single gene “for” language (even a regulating gene, like FOXP2) is an illusion, albeit an attractive one. What the Neanderthals possessed was a necessary condition for language, but it wasn’t sufficient.

  So far at least, then, there are no “silver bullet” genes that we can finger as the root cause of our cognitive uniqueness. But it turns out that there is a much better general explanation for our possession of a brain anatomy that facilitates complex thought: one that, moreover, fits far better with the little we know of the behavioral record at the time this uniqueness seems to have begun expressing itself. The specifics still evade us, and we have as yet no idea what the genetic rearrangement was that gave rise to the unique anatomy of Homo sapiens. All we know for sure is that this event did indeed occur. But it seems overwhelmingly likely that—like all of our other unique attributes of structure—our new cognitive ability was acquired as a byproduct of the hugely ramifying genetic accident that resulted in the appearance of Homo sapiens as a distinctive entity. Happily for us, the resulting creature turned out to function pretty well.

  In this view, the addition of the neural ingredient that predisposed our species for symbolic thought was simply one passive consequence of the developmental reorganization that gave rise to anatomically recognizable Homo sapiens some 200 thousand years ago. And it seems justifiable to look upon what happened as analogous to the construction of an arch, which cannot function until the keystone has been dropped into place. What’s more, whatever the “keystone” was in our case, the new potential it created then lay fallow for a substantial length of time, until its symbolic potential was “discovered” by its owner.

  Although it may seem a little counterintuitive, this time lag between the acquisition of what turns out to be a very significant novelty and its exploitation by its possessor, is actually an example of a very common phenomenon in the evolutionary history of life. Since all genetic innovations occur at random relative to the circumstances of their carriers’ existences (though they may be channeled, of course, by their owners’ evolutionary histories), they must arise initially not as adaptations to a particular lifestyle, but as exaptations: features that must necessarily be co-opted post hoc into a new use. I’ve already briefly mentioned the classic example of feathers, which were possessed by the ancestors of birds many millions of years before these modified dermal follicles were ever recruited as essential components of the flight mechanism. Similarly, the ancestors of terrestrial vertebrates had already acquired the rudiments of legs while they were still fully aquatic, and a terrestrial existence was still far in their future. You simply wouldn’t have predicted their future function when they first appeared. What is more, evolutionary novelties often persist if they don’t actively get in the way; and in the case of Homo sapiens the potential for symbolic thought evidently just lurked there, undetected, until it was “released” by a stimulus that must necessarily have been a cultural one—the biology, after all, was already in place.

  Cross-sections through the heads of a modern human (left) and a Neanderthal (reconstructed; right), to show differences of the upper vocal tract. Note the long palate and tongue of the Neanderthal, and the higher placement of its larynx compared to the Homo sapiens. Illustration by Diana Salles, after sketches by Jeff Laitman.

  This biology included not only the cerebral potential for generating language and passing instructions for its production along to the peripheral vocal structures, but also those peripheral structures themselves. There has been a lot of argument over just what it is about our upper vocal tract that allows us to produce speech, and without which our audible language could not be expressed. Much of this discussion has involved the low position in the human throat of our larynx (voice box), and how you might recognize in fossils exactly where the larynx lay. The lower the larynx is, the more pharynx (airway) there is above it that can be manipulated, by the throat muscles, to produce the frequencies that emerge as sound from the vibrating air column. Many have found reason to believe that larynxes were lowered to varying degrees in an assortment of fossil Homo crania, sparking speculation that language abilities (and by extension, human-style consciousness) began forming early in the evolution of our genus. Yet even the discovery of fossil hyoids (the bony part of the larynx) has done nothing much to quell argument over this matter, and lately attention has shifted toward the proportions of the oral and throat portions of the upper vocal tract, and to the suggestion that a short face is necessary to allow production of the necessary range of frequencies. We can expect debate about these features to continue.

  Meanwhile, though, there is a very attractive feature of the notion that the potentials for language, for speech and for symbolic thought were instead born together, at the origin of anatomical Homo sapiens. This is, that all of the necessary features would already have been in place by the times that they were co-opted (independently) for their new uses. Among other things, whatever functional context the short, retracted face of Homo sapiens had evolved in, it had nothing to do with language or perhaps even speech. It is hard to tell just what the actual context might have been, especially since a small, retracted face comes with s
ome significant disadvantages. For one, it reduces the length of the tooth-rows, crowding the teeth and frequently leading to impactions and malocclusions; for another, lowering the larynx involves a crossing of the airways with the food tract that introduces a severe danger of choking—something that is much less likely when the larynx is high. This effect is more than an inconvenience; in Japan alone, famous for its bite-sized foods, more than 4,000 people choke to death every year. It’s anybody’s guess what the countervailing early advantages of the new skull form might have been. Maybe the disadvantages just weren’t enough to make a significant difference, or maybe the slender new body build was energetically economical enough to provide a competitive advantage with more massively constructed and lower-mileage competing hominids. But clearly, what proved up to the job was the new and unusual human organism as a whole, rather than specific aspects of its innovative anatomy.

  Still, early Homo sapiens did not overwhelm the competition right away. As we have seen, its initial and apparently unsymbolic foray into the Levant was not a permanent success. Instead, the rapid takeover of the world by our forebears had to await the arrival of symbolic behavior patterns. The spotty evidence we have of mankind’s symbolic awakening does not rule out either of two possibilities as to just how this development happened within the African continent. Given that the biological potential was already present, multiple isolated hominid populations in various parts of Africa might have started experimenting with the new ability; or there was just a single point source. Knowing for sure which was the case will require a lot more information than we have at present, though the broad distribution of early rumblings suggests that, at the very least, symbolic information processing was an idea whose time had arrived by 80 thousand years ago.

  SYMBOLIC AWAKENINGS

  Exactly how the almost unimaginable transition to the symbolic mental manipulation of information took place remains a subject of pure speculation, though an irresistible one. We have already established that we need to look for a cultural stimulus that kicked the biologically preenabled human brain into symbolic mode. If you asked an assortment of scientists interested in this question what that stimulus might have been, two clear frontrunners would probably emerge.

  One of these potential stimuli is “theory of mind.” We humans are primates, and our higher primate relatives in general are intensely sociable. Yet we display a particular kind of sociality, characterized not only by the kind of prosociality—concern for others—that the apes don’t seem to share, but also by a more detached, observational sociality. We know what we are thinking (known to psychologists as “first-order intentionality”), we can guess what others are thinking (second-order), we can suspect that someone else has a belief about a third party (third-order), and so on. Apes seem to have achieved first-order intentionality, and alone among nonhuman primates may have clambered on to the second level; humans, on the other hand, seem to be able to cope with up to six levels of intentionality before their heads begin to spin (he believes that she thinks that they intend . . . and so on). Some scientists believe that that the evolution of our extraordinary cognitive style was driven by the development of the increasingly elaborate theory of mind needed to cope with the dynamics of interaction within societies that were steadily becoming more complex. In other words, modern human cognition developed under the self-reinforcing pressures of increasingly intense sociality—maybe around those campfires.

  This is an attractive idea, especially as our elaborate social rituals and responses are so intimately interwoven with our ways of processing information about our fellow members of society—always a subject of intense preoccupation to us. But a mechanism of this kind explains neither why the highly social apes haven’t developed a more complex theory of mind over the time during which they have been evolving in parallel with us, nor why the archaeological record seems to indicate a very late and essentially unheralded arrival of symbolic consciousness in just one lineage of large-brained hominid.

  The other thing everybody associates with our cognitive style is our use of language. Indeed, it is hardly overstating the case to characterize language as the ultimate symbolic activity, allowing as it does the generation of an infinite number of statements from a finite group of elements. Like thought, language involves dissecting the world around us into a huge vocabulary of symbols that are then combined, according to rules, to make statements not only about the world as it is directly perceived, but also as it might be. And it is virtually impossible to imagine our thought processes in its absence, for without the mediation of language those thought processes would be entirely intuitive and nondeclarative, merely involving the association of incoming stimuli with remembered ones, and responding accordingly. This is not to say that responses of that kind need necessarily be simple. Extremely complex associations may be made without requiring the process of abstraction that lies at the basis of symbolic thought. We know this from the example of earlier hominids. These precursors did not just get by on this level of functioning, but made some of the most notable technological advances in hominid history, including the domestication of fire, the invention of compound tools, and the building of shelters. Such achievements are impressive indeed. But language facilitated the imposition of symbolic information processing upon older cognitive processes. And this added an entirely new dimension to the way in which hominids saw the world, and eventually reimagined it.

  That this momentous event took place in Africa—the continent in which we find the first fossil evidence of creatures who looked just like us, and (somewhat later) the earliest archaeological suggestions of symbolic activities—is corroborated by a recent study of the sounds used in spoken languages around the world. The study of comparative linguistics makes it clear that languages have evolved much as organisms have done, with descendant versions branching away from the ancestral forms while still retaining for some time the imprint of their common origins. Many scientists have accordingly used the differentiation of languages as a guide to the spread of mankind across the globe. And in doing this they have traditionally concentrated on the words that make up those languages. But this has proved a tricky endeavor, for individual words change quite rapidly over time: so rapidly that beyond a time depth of about five thousand years, or ten at the very most, it turns out to be fairly hopeless to look for substantial traces of relationship. As a result, while language has indeed proven useful in tracing the movement of peoples around the Earth over the last few thousand years, linguists have been somewhat stymied when it comes to its very early evolution.

  The New Zealand cognitive psychologist Quentin Atkinson has recently suggested an alternative. According to Atkinson, in seeking the origins of language we are better off looking not at words as a whole, but at the individual sound components—the phonemes—of which they are comprised. This makes sense, because the phonemes are much more bound by biology than are the ideas that their combinations represent. And when Atkinson looked at the distribution of phonemes in languages around the world, he found a remarkable pattern. The farther away from Africa you go, the fewer phonemes are typically used in producing words. Some of the very ancient “click” languages of Africa, spoken by people with very deep genetic roots, have over a hundred phonemes. Our English language has about 45; and in Hawaii, one of the last places on Earth to be colonized by people, there are only 13. Atkinson attributes this pattern to what is known as “serial founder effect”: a phenomenon, well known to population geneticists, that is due to the drop in effective population size each time a descendant group buds off and spreads away from an ancestral one. With each successive budding, genetic—and apparently also phonemic—diversity diminishes, because of the bottleneck effect discussed earlier.

  The signal of this effect in the five hundred or so languages analyzed by Atkinson is weaker than the one found in the genes, but this difference is plausibly due to the rapidity with which languages evolve. The key thing, though, is that the genetic and phonemic patt
erns are essentially the same, and that both point to an origin in Africa. Atkinson’s analysis suggests that the convergence point may be in southwestern Africa, which is also in line with one recent genetic study. And his results imply not only that modern Homo sapiens originated in a single place, but also that the same thing was true for language (or at least, for the form of language that survives today). In which case, there is a strong argument for a fundamental synergy between biology and language in the rapid takeover of the world by articulate modern people.

  THE TRANSITION

  There are many reasons why the invention of language is the obvious candidate for the stimulus that tipped our ancestors over the symbolic edge. Although all modern societies are already linguistic, and have been for a long time, we do know from direct observation that structured pidgin languages that substitute signing for sounds can be created quickly, and without external prompting. The most famous example is a signed language spontaneously developed by deaf children in Nicaragua during the 1980s. When the first schools for the deaf were established in that country during the 1970s, they brought together children who had formerly been isolated at home, among speaking relatives who did not sign. Forming a deaf community for the first time, the kids rapidly and independently created a signed language of their own: one that quickly developed many of the complexities of spoken language, though it bore no relation to the Spanish that was spoken around them.

  What’s more, in an incredible story, an adult human has been observed going through the process of acquiring language, a procedure that clearly involved a dawning recognition that objects can have names, the most basic of symbols. In her book A Man Without Words, the sign-language expert Susan Schaller affectingly describes how she realized that a deaf student in her class not only was unable to sign, but was unaware that other people used names to denote objects. This man, whom she called Ildefonso, had been brought up in a hearing household, in isolation from any stimuli that could have helped him grasp that objects had names. What’s more, he lacked access to any kind of special education that might have taught him to mentally create and recognize signs. Yet, although withdrawn, he functioned well enough to find his way into Schaller’s classroom, and once there, he immediately gave her the impression of being both intelligent and intellectually curious. As she tells it, Schaller initially tried to teach Ildefonso the rudiments of American Sign Language (ASL), but soon perceived that he did not grasp even the concept of signs. Modifying her approach, she eventually achieved a breakthrough. Ildefonso, in a flash of insight, understood that everything had a name. “Suddenly he sat up, straight and rigid. . . . The whites of his eyes expanded, as if in terror. . . . He broke through. . . . He had entered the universe of humanity, discovered the communion of minds.” This changed everything about his perception of the world, and, once he had recovered from the emotional flood his dawning comprehension unleashed, he became hungry for signs, demanding new words.