Homo Mysterious: Evolutionary Puzzles of Human Nature (29 page)

“Once there were a Pig, and a Accordion, and two jars of Orange-marmalade … .”

When it comes to evolutionary hypotheses for the arts, this one has been vilified almost as much as Pinker’s cheesecake—especially by humanists worried that their subject is getting insufficient deference, and who also, it must be said, don’t understand evolutionary theory as well as they ought. In a nutshell, it involves what Darwin called “sexual selection.” And it was given its clearest formulation by evolutionary psychologist Geoffrey Miller of the University of New Mexico.
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Miller’s thesis is simple, yet profound. As he sees it, the human mind evolved as a result of sexual selection, essentially the equivalent of the peacock’s tail, except that among peacocks, the key choosers are the females, whereas in our case, the choice generally works both ways: males choosing females as well as females choosing males.

In any sexually reproducing species, it is highly adaptive for would-be parents to select the best possible partner with whom to reproduce. Several factors converge in this regard. For one thing, mate-seeking individuals will be more fit (evolutionarily) in proportion as their breeding partner is healthy and fit (physically). For another, since sexual reproduction involves combining one’s genes with someone else’s, it is important that the chosen someone possess genes that are likely to contribute positively toward producing healthy and successful offspring. In addition, once individuals of either sex are attractive to members of the other, there arises a secondary, derivative benefit from mating with such individuals: They are likely to produce offspring who also possess these sexually attractive traits, and who therefore will be more likely to be successful themselves when they mature and enter the mating marketplace. Finally, these considerations are likely to be especially valid in species that are at least somewhat monogamous, that is, in which males and females make a substantial commitment to each other, which in turn italicizes the importance of making a reproductively advantageous mate choice.

In his book,
The Mating Mind
, subtitled
How Sexual Selection Shaped the Evolution of Human Nature
, Miller gets abundant explanatory mileage out of sexual selection, and not simply as an explanation for the arts. In fact, he isn’t directly concerned with explaining the arts as such, so much as spotlighting the role of sexual selection in producing the human mind, in all its remarkable complexity. He points out, for example, that the brain itself—an energetically expensive organ as well as one that is highly vulnerable to mutational damage—serves as an ideal fitness indicator, a kind of biological trophy displayed by members of one sex that serves to attract members of the other.

This is similar to the brain’s products, and not just obviously useful behavior of the sort that contributes to individual survival.
Also relevant: those uniquely human characteristics that have so bedeviled generations of evolutionary biologists and are the subject of this chapter, namely, art, music, dance, poetry, and other manifestations of creativity that seem unlikely to contribute directly to fitness. Sexual selection promises to shed light even on certain human traits that might not otherwise appear to need special explaining … until we look at them through its uniquely illuminating lens.

Take language.

Miller makes a powerful case that human language exhibits a verbal luxuriance that is difficult to interpret in other than sexually selected terms. Bear in mind that Darwin originally conceived the concept of sexual selection in an effort to explain the existence of such exaggerated, highly elaborated, and seemingly useless traits as the lyrebird’s feathers or—most famously—the peacock’s tail. His argument—controversial in its day but increasingly supported now—was that although certain characteristics don’t contribute to personal survival (and may even be deleterious), they ultimately pay their way in terms of reproductive success insofar as they contribute to an individual’s ability to attract and keep a mate, hence the phrase “sexual selection.”

At first glance, human language does not seem equivalent to the peacock’s tail. After all, the peacock’s tail is the iconic example of something that seems excessive, overbuilt—indeed, deleterious—and thus explicable only in terms of sexual selection rather than survival selection. By contrast, although the adaptive significance of human language may not be obvious, the problem isn’t that language—like the peacock’s tail—is difficult to explain, but rather that it is explicable in terms of numerous possible adaptive payoffs: social coordination, sharing of information, and so forth, such that the very fact of language does not seem to qualify as an evolutionary mystery. And yet, as Miller points out, human language may be more like a peacock’s tail than is generally realized.

Like the peacock’s tail, human language is more elaborate than simple survival would seem to require. One way to assess this would be to compare the minimum vocabulary needed to satisfy basic, quotidian tasks with the actual vocabulary most people possess. Miller points out that most of the words that most people
know are used only rarely. Why, then, he asks, do we retain such a large stable of largely unused resources?

The most frequent 100 words account for about 60 percent of all conversation; the most frequent 4,000 words account for about 98 percent of conversation. This sort of “power law” distribution is common: the 100 most successful movie actors probably account for 70 percent of all money paid to all actors; the 100 most popular Internet sites probably handle a similar proportion of Internet traffic; and so forth. It is not surprising that vocabulary use follows a power law, but it is surprising that our average vocabulary is so large, given how rarely we use most of the words that we know. It could easily have been that just 40 words account for 98 percent of speech (as it does for many two-year-olds), instead of 4,000 (as it does for most adults). As it is, any of the words we know is likely to be used on average about once in every million words we speak. When was the last time you actually spoke the word “cerulean”? Why do we bother to learn so many rare words that have practically the same meanings as common words, if language evolved to be practical?

The plot thickens when we consider that even English—which hosts an exceptionally large number of words, numbering more than 1 million—can still function effectively after being stripped down to a mere skeleton. Thus, something called Basic English was created in the 1920s, using just 850 words. One of its co-creators, Oxford philosopher I. A. Richards, noted that under his system and using, for example, just 18 verbs, “it is possible to say … anything needed for the general purposes of everyday existence—in business, trade, industry, science, medical work—and in all the arts of living, in all the exchanges of knowledge, desires, beliefs, opinions, and news which are the chief work of English.”
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Missing from this assessment is a likely “chief work” of any language: demonstrating one’s intelligence, via verbal facility. As Miller notes, one would not expect to see a personal ad that said “looking for prospective mate who knows fifty thousand useless synonyms,” and yet, it is entirely possible that people have evolved outsized vocabularies for exactly the same reason that peacocks have evolved outsized tails, because tale telling—and the ability to employ appealing words in the process—suffices for people like tail growing works for peacocks.

In the language of evolutionary biology, such traits are effective “fitness indicators,” and as such, likely to be selected for because they contribute to sexual and thus reproductive success, no less than, say, the ability to ward off infection contributes to survival and thus reproductive success. This emphasizes a frequent misunderstanding of sexual selection, in which it is seen as somehow counter to survival (or natural) selection. There are, indeed, some interesting differences, notably the fact that whereas survival selection tends to be a minimalizing process, eliminating gewgaws and doodads, favoring a biological design that is maximally efficient, sexual selection generates excessive, show-offy traits. But sexual selection is no less “natural” than is survival selection, and indeed, both operate via the same bottom line: differential reproduction.

There is one intriguing difference, however. Although both sexual selection and survival selection are equally natural and reproduction focused, the former is oddly recursive. When it comes to survival selection, the totality of the environment (physical as well as biological) operates upon organisms to favor certain characteristics over others. This has some impact upon environments as well—the dietary proclivities of elephants, for example, have had a definite impact on the nature of the African savannah—but by and large, environments select for organisms and not vice versa. With sexual selection, however, the organisms themselves are bestowing reproductive advantage upon members of their own species, favoring some of them over others. Insofar as sexual selection has been especially important among
Homo sapiens
, the result is that to an extent not often appreciated (by scientists as well as the lay public), human beings have literally created themselves.

Contrasting sexual selection with survival selection, Miller emphasizes the unique feedback component of the former, as he speculates playfully on what would happen if natural selection worked like its sexual counterpart:

Organisms would select which environments exist, as well as environments selecting which organisms exist. Strange, unpredictable feedback loops would arise. Would the feedback loop between polar bears and Arctic tundra result in a tundra of Neptunian frigidity where bears have fur ten feet thick, or a tundra of Brazilian sultriness where bears run nude? Would migratory birds select for more convenient winds, lower gravity, and more intelligible constellations? Or just an
ever-full moon that pleasingly resembles an egg? Yet this is just what happens with sexual selection: species capriciously transform themselves into their own sexual amusements.

Courtship involves sexual choice, which, in turn, places a positive premium on “fitness indicators,” characteristics that provide reliable information as to the adaptive quality of a prospective mate. As such, sexual choice itself served to stretch the capacities of the human mind, even as it rewarded those who indicated—via such mental gymnastics as verbal play, musical ability, and other manifestations of artistic creativity—that their brains were in especially good shape. As Miller puts it, sexual selection “asked not what a brain can do for its owner, but what fitness information about the owner a brain can reveal.”

Miller points out, for example, that to a large extent, human courtship involves verbal interaction, and that baby making (one of the bottom lines when it comes to evolutionary success) requires about 3 months of unprotected sex, which, at roughly 2 hours of conversation per day in the early stages of an intimate relationship, and an average rate of 3 words spoken per second, results in roughly 1 million words spoken by each partner … per conception. In this way, sexual selection might contribute directly to fitness, via such seemingly “useless” traits as verbal facility.

After all, there is nothing like talking to reveal not only what’s on one’s mind but also the nature and quality of that mind. And for human beings, ancestral no less than current, the mental status of a potential reproductive partner was likely to loom large indeed.

Cross-cultural surveys of mating preferences across a variety of cultures have shown a strong preference for, among other things, a sense of humor. Being able to tickle your partner’s funny bone might be a useful indicator of something immediate and practical, such as the ability to withstand future difficulties and disappointments. But the reality is that a good sense of humor, like a powerful vocabulary, is no more likely to be of direct survival value than is—to choose some activities not entirely at random—the ability to tell a good story, sing a song, paint a picture, write a poem, sculpt a statue, and so forth. In short, the argument can be made (or, in more suitably florid linguistic terminology, the scientific hypothesis propounded) that verbal facility, like competence in
music, visual art, dance, and the like, may have evolved in the service of sexual selection, a way in which the artist demonstrates his or her cerebral fitness and, insofar as the demonstration is successful, actually increases his or her evolutionary fitness as a result.

Here is another point. A narrow survival selection view of language would generate the prediction that listening should be more beneficial and thus more sought after than speaking since, after all, we learn (and thus stand to profit personally) via the former, rather than the latter. But in fact, people are more likely to compete to be the one broadcasting “information” than to be its recipients. This, in turn, is consistent with the notion that language itself may be largely a form of display (although it also conforms to the sociobiological view that communication is often manipulation
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). At the same time, much sexual display is not simply “epigamic”—directed toward mate choice—but also effective when it comes to male–male or female–female competition.

The key to the sexual selection hypothesis is that many traits aren’t fitness enhancing so long as we restrict our intellectual horizon to those that are strictly survival related. Widen the perspective, however, to include mate choice, and a whole new world opens up, with much of the human mind seen to be a sexual ornament. “The Darwinian revolution could capture the citadel of human nature,” writes Miller, “only by becoming more of a sexual revolution—by giving more credit to sexual choice as a driving force in the mind’s evolution. Evolutionary psychology,” Miller urges, “must become less Puritan and more Dionysian.” His project has therefore been to think less about the “survival problems our ancestors faced during the day” and more about “the courtship problems they faced at night”—or, more poetically, “whether the mind evolved by moonlight.” Ditto for the arts.