The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature (52 page)

This Pleistocene fantasy could be criticized on many counts. It may overestimate the awareness of mammoths, though I doubt it, since their brains were five times the size of ours. It may over-estimate the hunting ability of our recent ancestors, though I doubt that too, since there is fairly good evidence that they hunted many species of mammoths, mastodons, and elephants to extinction in the last hundred thousand years. The real problem with most fantasies like this is that they show the telepathy-like power of language being used only in the struggle for survival. Doubtless language was useful in coordinating hunting, as it was in many survival activities. But language was also sure to be useful in courtship. In this chapter I shall put survival selection to one side, and consider how our ancestors developed the ability to fall in love by talking to each other.

Forget Chomsky and Kanzi!

The history of research on the evolution of language resembles the history of sexual selection theory. Darwin had some good ideas, then scientists got distracted for a century by the wrong questions, and only recently took up where Darwin left off. In
The Descent of Man
, Darwin proposed that language evolved gradually through sexual selection, as an instinct to acquire a particular method of verbal display similar to music. He recognized that language, like conceptual intelligence and principled morality, was an unusual human adaptation deserving a serious evolutionary analysis. Yet after Darwin, there followed a century of speculations about language origins which focused on tangential issues like "ape language" and the "innateness" of language. Only recently have we come back to Darwin's viewpoint, where we can once again ask what the adaptive functions of language may have been.

The ape language controversy was unenlightening because we already knew that chimpanzees do not naturally talk. The fact that they do not suggests that the last common ancestor we shared with chimpanzees, five million years ago, did not talk either. Language therefore evolved in the last five million years. If a human adaptation clearly evolved after the split from our last common ancestor with chimps, there is no more reason to look for rudiments of language in chimps than in baboons, beavers, or birds. The trained use of visual symbols by very clever individual apes like the famous Kanzi is marginal to understanding the evolution of human language.

The situation would have been very different if the other species of hominid had not all gone extinct. We could potentially learn a great deal about language evolution if there were still living descendants of
Australopithecus robustus
(a small-brained, strong-jawed bipedal hominid), Asian
Homo erectus
(a medium-brained hominid offshoot), and European Neanderthals (a large-brained, near-human species). As it stands, to discover whether Neanderthals talked, we would have to identify a lot more of the genes underlying human language, and then test the scraps of Neanderthal DNA that we can recover from their bones to see if

they share the same genes. That might take another couple of decades. The presence of language in Neanderthals would tell us much more about the evolution of human language than the absence of language in chimpanzees does.

The other 20th-century controversy about language concerned its "innateness." The language theorist Noam Chomsky and other language "nativists" fought hard against the social science dogma that all human mental abilities are products of learning. It was a heroic fight, but for our purposes all we need to know is that the nativists won. Steven Tinker's excellent book
The Language Instinct
reviewed why they won. Pinker listed the features of language that mark it as a proper biological adaptation: "Language is a complex, specialized skill, which develops in the child spontaneously, without conscious effort or formal instruction, is deployed without awareness of its underlying logic, is qualitatively the same in every individual, and is distinct from more general abilities to process information or behave intelligently." These features show that language really is a human instinct, a mental adaptation. But they are common to all of our mental adaptations. Our capacities for language, depth perception, face recognition, sexual attraction, autobiographical memory, and social planning are all specialized skills— spontaneously learned, unconsciously deployed, and universally enjoyed. These features do not help to identify exactly what adaptive functions were served by language. They show that it evolved, but not why it evolved.

Chomsky's own research had the same limitation. He offered convincing arguments that children could not possibly learn the fundamental syntactic principles of language through parental feedback or formal instruction. This demonstration undermined the 1950s behaviorist view of language as a learned cultural invention. But Chomsky's demonstration that language depended on innate genetic capacities failed to give' him any useful insights into how it evolved. In fact, Chomsky has rejected the possibility that language evolved through normal Darwinian processes.

This is a common reaction. Sometimes researchers can get so caught up in demonstrating an adaptation's complexity, elegance,

and innateness that they can no longer imagine how the adaptation could have evolved through normal Darwinian processes. Alfred Russel Wallace fell into this trap when he analyzed human rationality morality, and musical ability. When healthy respect for an adaptation tips over into awe, it becomes impossible to make any progress in understanding the selection pressures that shaped the adaptation. Like Chomsky, many researchers interested in the evolution of language suffer from this awe-of-language syndrome. Chomsky has even speculated that any sufficiently large brain (like that of a mammoth?) might automatically develop the capacity for language as a mysterious side-effect of packing 100 billion nerve cells into a small volume of space. To avoid the intellectual paralysis that the awe-oflanguage syndrome sometimes produces, I shall not review here the evidence for language's power and complexity—Steven Pinker has already done an excellent job of that in
The Language Instinct

More has been written about language evolution than about the evolution of any other specific human mental ability. However, very little of this writing has been genuinely adaptationist in the sense of assessing particular fitness benefits that could have driven the evolution of language. Very few "theories of language evolution" identify particular selection pressures that could favor the gradual accumulation of genetic mutations necessary to evolve a complex new mental capacity that has costs as well as benefits.

The current debate no longer concerns whether language is an adaptation, but what it is an adaptation for. It seems so easy to imagine survival functions for language that its possible sexual functions have been overlooked. Postulating survival functions has the appeal of the exotic, because we can daydream about mammoth hunts, tribal wars, and flint-knapping from the comfort of our armchairs. Verbal courtship is less fun to think about, perhaps because it may remind us of failed attempts at self-introduction, disastrous first dates, ardent self-revelations that met with cold, pitying stares, broken promises of fidelity, and relationship-terminating arguments. From the viewpoint of any normal

living individual, all of one's past survival attempts have succeeded, whereas most of one's past courtship attempts have failed. (If most of your courtship attempts have succeeded, you must be a very attractive and charming person who has been aiming too low.) This, I think, is a useful clue: it is easier to live with language than to court with language.

Selfish Language: Communication,
Manipulation, or Display?

The trouble with language is its apparent altruism. Most speech, except for commands and questions, appears to transfer potentially useful information from speaker to listener. Speaking costs the speaker time and energy, and brings information benefits to the listener, so it looks altruistic. But, as we saw in the last chapter, evolution tends to avoid altruistic behavior.

Fifty years ago, altruistic communication did not seem such a problem. The animal behavior researcher Konrad Lorenz supposed that communication was for the good of the species. Animals could save their species lots of time and energy by evolving signals that reveal their intentions and motivations, especially in combat and courtship. This would reduce the deaths from combat and the confusions of courtship. Ritualized threats such as a dog's growling were supposed to convey accurate information about the dog's level of aggression and willingness to fight over a resource. If a growly dog meets a non-growly dog, the non-growly dog should back down, saving the species a wasteful dogfight. For several decades, the biologists' dogma was that animal signaling meant communication, communication revealed emotions and intentions, and communication evolved to make a species work more efficiently.

The rise of selfish-gene thinking in the 1970s shattered this idyllic view of animal signaling. Traits did not evolve for the good of the species. In their seminal 1978 paper, Richard Dawkins and John Krebs argued that animals should evolve to produce signals only when signaling gives them a net fitness benefit that helps their own genes replicate at the expense of other genes. Evolution

cannot favor altruistic information-sharing any more than it can favor altruistic food-sharing. Therefore, most animals' signals must have evolved to manipulate the behavior of another animal for the signaler's own benefit. Dogs growl because it was easier for them to intimidate a rival than to fight. Smaller dogs could be intimidated by deep growls because a deep growler is probably a larger dog that would beat them in a fight anyway. Both the growl and the growl-sensitive ears evolved for selfish reasons.

The modern theory of animal signaling grew from this insight. Signals don't usually convey information about the world, because signalers have so many reasons to lie about the world. The theory suggests that animals usually evolve to ignore the signals from other animals that may be attempting to manipulate them. There are only a few exceptions. Predators listen to signals from prey that reliably say "You can't catch me," or "I'm poisonous." (Animals hiding from predators also evolve camouflage, the purpose of which is to hide signals of existence rather than to broadcast them.) Relatives listen to signals from other relatives that reliably say "Watch out for that predator!" Animals competing for a resource listen to signals that reliably say "I could kill you." And animals looking for a good mate listen to signals that say "I have good genes." Basically, that's it. Except for the warning signals about poison and predators, these signals are all fitness indicators. Any other kind of signal that evolved in nature would probably be pure manipulation, making the listener vulnerable to lies, sweet talk, and propaganda.

The handicap principle can make fitness indicators reliable. It can do so because the signal's cost is in the same currency—the currency of biological fitness—as the signal's information. This can work not only for fitness indicators that advertise good condition to potential mates, but for signals of desperation that advertise poor condition to relatives. For example, the handicap principle may also account for the effectiveness of a baby bird's gaping-mouth hunger display. Desperation signals also work with the currency of fitness: the animal reliably shows how much a desired resource would improve its fitness. Basically, fitness

indicators advertise good condition and desperation indicators advertise poor condition. Signals between unrelated animals can convey information only about the signaler's own condition, broadly construed. There are no credible models showing that evolution can favor signals that carry any other kind of information, as long as there are incentives for deception.

This is a crippling problem for almost every existing theory of language evolution, but the problem is not widely understood. The handicap principle is not a magic wand that makes all communication truthful just because a speaker has paid a fitness cost. It cannot guarantee that a sentence conveys valid information. For example, just because someone accepted the pain and risk of infection necessary to get a tattoo does not make the tattoo's message valid. It just implies that the tattooed person is stoical and healthy.

Anthropologist Chris Knight has emphasized that human language is especially vulnerable to deception because it depends so much on "displaced reference"—referring to things that are distant in time or space. To a person dying of thirst, we can say, "There's a river over that hill." But displaced reference is hard to verify. We might be lying about the river, and the thirsty person might die if he goes over the hill expecting to reach a river and finds a desert instead. In fact, there are no theories of animal signaling in which reliable displaced reference could evolve, given significant conflicts of interest between signaler and receiver. Bee dances use displaced reference to indicate the direction and distance of food, but the bees are sisters from the same hive, so they have common interests. Between our Pleistocene ancestors there were always conflicts of interest, so it is very hard to see how reliable displaced reference could have evolved. If displaced reference was not reliable, listeners would not have bothered to listen, so speakers would not have bothered to speak.

This brings us back to the altruism problem. At first it sounds plausible to suggest that "language evolved to convey propositional information from one mind to another." But that raises the

question of why the speaker should altruistically give away information to an evolutionary competitor. Truthful communication is rare in nature because altruism is rare. As we saw in the previous chapter, naive altruism theories cannot explain human morality. Why should we invoke them to explain human language?

To explain language evolution, then, we need to do the same things we did for morality: find a hidden survival or reproductive benefit in the apparently altruistic act of speaking. As with morality, there are three basic options for the hidden benefit: kinship, reciprocity or sexual selection. The fitness benefits of speaking must have come from giving useful information to a relative, sustaining a mutually beneficial information-trading relationship, or attracting a mate. I am sure all three were important, and I am not going to claim that sexual choice was the only selection pressure that shaped human language. However, I do want to highlight some features of how people talk that are not very consistent with the kinship and reciprocity theories.