Masters of the Planet (36 page)

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
ad
aptations to a particular lifestyle, but as
ex
aptations: 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 some 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.