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The Human Nature Review Human Nature Review  2002 Volume 2: 187-194 ( 13 May )
URL of this document http://human-nature.com/nibbs/02/barash.html

Essay Review

What’s A Brain For?
David P. Barash*

A Brain For All Seasons
By William H. Calvin
341 pp, University of Chicago Press (2002)

The Mating Mind
By Geoffrey Miller
503 pp, Doubleday (2000; in paper Anchor Books: 2002)

I recall an old joke - of the type known generically in the US as a “shaggy-dog story” - that involved a “potfer.” After several minutes of lengthy and irrelevant narration, the joke’s victim is led to ask, “What’s a potfer?” whereupon the joke-teller triumphantly announces the punch-line: “Cooking.” So, what’s a brainfer? Most people would answer “Thinking.” Most evolutionary biologists, however, are likely to disagree, pointing out that the adaptive significance of brains isn’t thought but rather, promoting the fitness of bodies within which they reside … or, more precisely, the fitness of those genes that are responsible for producing the brains in question.

Brains may or may not be good at making sense of the world, or thinking great thoughts, or providing vivid subjective experiences to its possessors, or adroitly controlling their bodies. It is even possible, one can imagine, to be too brainy for one’s own good, which brings up another story, this one told by the late Ian McHarg: It was the aftermath of World War III and our planet had been reduced to radioactive cinders. In the deepest recesses of the ocean, the few exiguous survivors - a motley group of primitive, amoeboid creatures - have just decided they are going to try once again, but before they separated, ready to initiate, once again, that old evolutionary process, they take a solemn vow: “This time, no brains!”

Brains, in short, can be a problem. For evolutionary biologists, they definitely are. The question is “Why did our brains become so large, so quickly?” which often boils down to “How do/did they contribute to fitness?” The answers have not been easy to obtain. Or rather, they have been too forthcoming. Just as Mark Twain once pointed out that it was easy to stop smoking - he had done it hundreds of times! - it is easy to identify the adaptive significance of the extraordinarily large human brain: it has been done dozens of times.

And so, we have hypotheses suggesting that human brainyness is a result of selection for tool use, tool making, cooperative hunting, defense against predators, defense against other protohumans, and so forth, not to mention the suggestion by Alfred Russell Wallace (of all people) that the elaborate functional complexity of our cerebrum, and its remarkable cognitive and artistic capacities, must be due to something - gasp! - supernatural. (Intelligent design for intelligence itself.) Oh yes, there is also Stephen Jay Gould’s patently absurd suggestion that our mental capacities must be a random, nonadaptive happenstance, specifically a result of “surplus” brain tissue. (The human brain is fantastically expensive to maintain, requiring an inordinate amount of metabolic energy; if brain tissue has ever been surplus, then it would long ago have been selected against, or turned into fat, not creativity. And although some people can be accused of being “fat-headed,” this isn’t the usual implication!)

Into this hodge-podge of hypotheses comes two books, both purporting to shed light on the mystery of our big-brainyness, and both, I suspect, containing some truth. Both are written by people with a fine grasp of evolutionary thinking, and both are well worth reading. At the same time, they are remarkably different in perspective.

In A Brain for all Seasons, neuroscientist William Calvin departs from his usual habitat - how brains function - to explore the possible role of one particular environmental factor in producing so spectacular a cerebral efflorescence. That factor is climate, particularly the growing consensus among atmospheric scientists that the Earth may have experienced a series of dramatic, even catastrophic heatings and coolings within the last few million years. The mechanism is complex, involving interruptions of the thermohaline circulation of the North Atlantic, as a result of increased freshening of its water, which in turn can be a consequence of brief but intense periods of - guess what? - global warming. The pattern, then, would entail heating (presumably non-anthropogenic) followed by dramatic and possibly even catastrophic cooling.

Upon first reading of this, I was skeptical, if only because it conjured up memories of Immanuel Velikowsky and other crackpot prophets of cataclysm. But a few consultations with colleagues in the atmospheric sciences has convinced me that even though I don’t fully understand the geophysics, a goodly number of respectable geophysicists evidently do, granting that a scenario of major climatic flip-flops, occurring every few thousand years but with an actual time-course of decades, even possibly years, is credible.

This is a good thing, at least for Calvin’s book if not for our future, because his argument relies on such “whiplash” climate cycles to have driven selection for large brains insofar as they conferred ability to adapt to rapidly changing environments. If, for example, rapid cooling produced lots of grassland, this would have resulted in a relative abundance of large grazing animals which, in turn, would have selected for the now-familiar “man the hunter” lifestyle.

Unfortunately, Calvin isn’t nearly as good explaining climate change as when explicating brain mechanisms. So we get a lot about Younger Dryas, tilt and precession, upwellings and down-sinkings, fjord floods of fresh water, oceanic heat-pumps and the like, most of which I simply take on faith. I’d have appreciated more evolution and less climate change; in particular, although there are many ways of interpreting how rapid climate change could have selected for large brains, it would have been helpful for Calvin to fill in some of the dots, if only with speculation.

William Calvin has a fondness for non-traditional book concepts, not just when it comes to the ideas expressed but also the means of expressing them. Thus, his earlier (and to my mind, best) effort, The River That Flows Uphill - a fine meditation on evolution and complexity - was presented as a series of conversations while rafting the Colorado River; Lingua ex Machina (with Derek Bickerton) emerged as a collection of letters; and, for some inexplicable reason, A Brain For All Seasons is a combination travelogue and “E-Seminar” … whatever that is. Maybe I’m just a curmudgeon, but what’s wrong with a regular, old-fashioned book? Especially since Calvin writes so clearly, at least most of the time.

He is an especially good man with a quip. Writing of the various efforts to summarize purportedly unique human traits, Calvin notes that “such ‘uniquely human’ lists have proved very useful in the past - because they stimulate ape researchers to disprove them!” (pg. 31), just as he adroitly refers to the “earlier than thou” competition among paleontologists (pg. 35), and observes, in an aside worthy of Ambrose Bierce, that “averages are just devices to keep us from thinking more deeply” (pg. 76). He is also a born teacher, handy with metaphors. Take this explanation of how changes in one aspect of structure can open the evolutionary door for other, seemingly unrelated functions:

It’s much like when wheelchair considerations paid for curb cuts but soon 99 percent of their use was for things that would never have paid their way - baby carriages, skateboards, wheeled suitcases, bicycles, and so on. Maybe one of those secondary uses will eventually pay for further improvements, but the ‘free lunch’ is alive and well in both urban architecture and biology (pg. 44).

Calvin’s thinking goes against the grain in some ways, beyond that of traditional book design, such as a peculiar receptivity for the “aquatic ape” hypothesis (although not going so far as the goofy enthusiast Elaine Morgan), and a soft spot for group selection: “Any individual that tended to give away food, or indiscriminately risk life and limb for non-relatives, would be a loser - unless living, by happenstance, in a subpopulation with a lot of other indiscriminate sharers … “ (pg. 92). But all branches of science, evolutionary biology included, could use a dose of out-of-the-box thinking. And this William Calvin provides, beginning with an effort to understand why the human brain evolved as it did, and ending with a powerful plea for climate stabilization.

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By contrast with A Brain For All Seasons - which is concerned entirely with “survival selection” - Geoffrey Miller’s The Mating Mind is focussed on the other major engine of evolutionary change: sexual selection. It’s an extraordinary and highly successful effort: insightful, scholarly, yet accessible. It also stimulated a genuine “Huxley moment,” in which I found myself exclaiming “How stupid of me not to have thought of that!”

Miller’s thesis is simple, yet profound: perhaps the human mind evolved as a result of sexual selection, essentially the equivalent of the peacock’s tail, except that in our case, much of the choice works both ways: males choosing females as well as females choosing males. Miller gets wonderful intellectual mileage out of this notion, pointing out, for example, that the brain itself, as an energetically expensive organ as well as one that is highly vulnerable to mutational damage, serves as an ideal fitness indicator. Similarly with the brain’s products, and not just obviously useful behavior of the sort that contributes to survival selection, but also those uniquely human characteristics that have so bedeviled sociobiological explanation: art, music, poetry, creativity, all of which seem unlikely to contribute to fitness.

But “Human language,” Miller points out,

evolved to be much more elaborate than necessary for basic survival functions. From a pragmatic biological viewpoint, art and music seem like pointless wastes of energy. Human morality and humor seem irrelevant to the business of finding food and avoiding predators. Moreover, if human intelligence and creativity were so useful, it is puzzling that other apes did not evolve them (pg. 2).

The point of The Mating Mind is that such traits probably aren’t fitness-enhancing, so long as we restrict our intellectual horizon to survival-related traits. Widen the perspective, however, to include sexual selection, and a whole new world opens up, in which much of the human mind is a sexual ornament: “the Darwinian revolution could capture the citadel of human nature 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” (pg. 7).

In Miller’s subtle approach, the mind’s moonlight reveals unexpected patterns; e.g. “before language evolved, our ancestors could not easily perceive one another’s thoughts, but once language had arrived, thought itself became subject to sexual selection” (pg. 10). This “doesn’t reduce psychology to biology, but sees psychology as a driving force in biological evolution. It portrays our ancestors’ minds as both products and consumers evolving in the free market of sexual choice” (pg. 16). Nonetheless, his critique of much cognitive psychology is cogent, and perhaps even devastating:

most experimental psychology vies the human mind exclusively as a computer that learns to solve problems, not as an entertainment system that evolved to attract sexual partners. Also, psychology experiments usually test people’s efficiency and consistency when interacting with a computer, not their wit and warmth when interacting with a potential spouse. … But evolution does not care about information processing as such: it cares about fitness (pg. 29-30).

It is indeed delightful to encounter someone trained as a cognitive psychologist who is so conversant, comfortable, and creative when it comes to such biological bailiwicks as the “lek paradox” and consequence debate over the heritability of fitness-related traits. (Incidentally, when it comes to evolutionary theory, Miller is far better informed than one of his prominent senior critics, anthropologist Ian Tattersall, whose purportedly critical review of The Mating Mind in the June, 2000 New York Times revealed more about Tattersall’s arrogant ignorance than about any weaknesses in the book he was undertaking to review.)

Contrasting sexual selection with survival selection, Miller emphasizes the unique feedback component of the former, revealing his own dazzling creativity 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 (pg. 69).

I apologize, by the way, for quoting so extensively, but part of the delight of The Mating Mind is that Miller’s prose is so imaginative, and so compelling, that it simply demands to speak for itself!

Thus, his metaphors are lovely, provocative, and worth repeating: “Fitness is like money in a secret Swiss bank account. You may know how much you have, but nobody else can find out directly. If they ask the bank, the bank will not tell them. If they ask you, you might lie. If they are willing to mate with you if your capital exceeds a certain figure, you may be especially tempted to lie. This is what makes mate choice difficult” (pg. 122), and, I might add, what makes Miller’s theory of brain evolution especially congenial to Zahavi’s “handicap principle,” an idea whose panache has lately been increasing.

Miller adroitly brings in Thorstein Veblen and the power of conspicuous consumption as sexual advertisement, asking “How could mate choice favor a costly, useless ornament over a cheaper, more beneficial ornament?” to which he adds, puckishly, “Why should a man give a woman a useless diamond engagement ring when he could buy her a nice big potato, which she could at least eat?” (pg. 124).

In the course of answering this question, Miller goes on to suggest possible roles for R. A. Fisher’s runaway process, for sensory biases, and for pleasure centers, giving the greatest weight, however, to fitness indicators. I have only a few areas of disagreement. First - ironically, for a book that argues its case so persuasively - I suspect that Miller gives up too easily on some of his own ideas, notably the possible role of runaway selection. He discounts its impact by claiming that runaway can only proceed at a very rapid pace, and that human brain evolution occurred, paradoxically, too slowly for it to be largely a product of runaway. I respectfully disagree. Depending on the degree of reproductive skew, selection can “run away” at anything from a moderate canter to a wild stampede; there is no predetermined rate at which runaway must necessarily proceed. Moreover, Miller himself worries (too much, I think) that our ancestors weren’t polygynous enough for sexual selection to be effective. In this regard, I suggest that he over-estimates the ubiquity and rigidity of early human monogamy: DNA-based data on extra-pair copulations increasingly testify to the fact that there is now, and presumably has always been, a lot of nonmonogamous screwing around (for more details see D. P. Barash and J. E. Lipton, The Myth of Monogamy: fidelity and infidelity in animals and people, 2002, Henry Holt & Co.).

A final disagreement: even as he may actually underestimate the effectiveness of sexual selection in some respects, I believe that Miller over-values its “good genes” component. Thus, sexual selection isn’t simply a matter of seeming (and being) sexy because you have revealed yourself to have fitness-enhancing genes. A potential sexual partner is looking for other “goods” as well, notably “good resources” as well as “good behavior.” Sometimes - as when a choosy female insists on being well-fed by an amorous male in return for sexual access - a good meal is just a good meal! (And fitness-enhancing as such.) By the same token, a prospective mate may prefer a partner who reveals him or herself inclined to good behavior such as skill at prey-catching, or inclination to exert him or herself against predators, not simply because an individual of this sort is likely to be carrying prey-catching or anti-predator genes - which could be inherited by mutually produced offspring - but also because it is fitness enhancing, in the here-and-now, to have a mate who is a reliable prey-catcher or predator-deflector.

But don’t misunderstand. The Mating Mind is an immensely stimulating work, full of important ideas for evolutionary psychologists no less than for general readers. “To traditional evolutionary psychologists,” Miller observes, “human abilities like music, humor, and creativity do not look like adaptations because they look too variable, too heritable, too wasteful, and not very modular. But these are precisely the features we should expect of fitness indicators” (pg. 132), since “sexual choice demanded courtship behavior that stretched the mind’s capacities. … It asked not what a brain can do for its owner, but what fitness information about the owner a brain can reveal” (pg. 135). In pointing this out so forcefully, Miller stretches our minds as well.

Thus, we get a fresh look at familiar facts. Among our ancestors, “If an individual made you laugh, sparked your interest, told good stories and made you feel well cared for, then you might have been more disposed to mate.” Miller then goes on, asking us to consider what happens in modern courtship. We take our dates to restaurants where we pay professional chefs to cook them great food, or to dance clubs where professional musicians excite their auditory systems, or to films where professional actors entertain them with vicarious adventures. The chefs, musicians, and actors do not actually get to have sex with our dates. They just get paid. We get the sex if the date goes well. Of course, we still have to talk in modern courtship, and we still have to look reasonably good. But the market economy shifts much of the courtship effort from us to professionals. To pay the professionals, we have to make money, which means getting a job. The better our education, the better our job, the more money we can make, and the better the vicarious courtship we can afford. Consumerism turns the tables on ancestral patterns of human courtship. It makes courtship a commodity that can be bought and sold (pg. 188).

He provides additional insights into his chosen domains of art, morality, language, and creativity. Just a hint comes from his refreshing perspective on art, in which he distinguishes “top-down” from “bottom-up” strategies, the former involving elite culture, created by those few possessing remarkable talent, the latter involving “folk aesthetics,” made by normal people. Miller emphasizes that the

Fitness display theory of aesthetics works much better for folk aesthetics than for elite aesthetics. Folk aesthetics concerns what ordinary people find beautiful; elite aesthetics concerns the objects of art that highly educated, rich elites learn are considered worthy of comment by their peers. With folk aesthetics, the focus is on the art-object as a display of the creator’s craft. With elite aesthetics, the focus is on the viewer’s response as a social display. In response to a landscape painting, folks may say, “Well, it’s a pretty good picture of a cow, but it’s a little smudgy,” while elites might say, “How lovely to see Constable’s ardent brushwork challenging the anodyne banality of the pastoral genre.” The first response seems a natural expression of typical human aesthetic tastes concerning other people’s artistic displays, and the second seems more of a verbal display in its own right (pg. 284).

Having pondered this, it would be difficult not to be more sympathetic to the “Philistine” assessment of, say, abstract expressionism that shrugs, “My child could have done that,” or “Looks more like an accident than like art.” Miller touches an important biological chord, whereby works of art are evaluated specifically as indicators of the artist’s talent and skill, rather than by what the work “says.” He requires us to cease condescending and ask why most people are so resistant to forms of art that do not reveal, clearly, the competence of the artist.

There is more, much more, including a lucid explanation of why men in particular are so prone to “spend huge amounts of time and energy doing useless sweaty things with one another” (pg. 312; think soccer, basketball, football, boxing, cricket, rugby, etc.), the possible functions of public morality as a courtship strategy, which, incidentally, sheds light on “why many people care so little about the efficiency of charities in transferring resources from givers to receivers” (pg. 322). In Miller’s interpretation, they are most interested in the giving as such, and in being perceived as having done so. Why? Sexual selection, once again.

Miller suggests that a narrow survival selection view of language would generate the prediction that listening should be more beneficial than speaking, whereas in fact, people are more likely to compete to be the one broadcasting “information” than to be its recipients. This, of course, is consistent with the notion that language itself may be largely a form of display (although it also conforms to the sociobiological view - championed by Richard Dawkins and John Krebs - that communication is often manipulation). It might also have been helpful to confront the fact that much sexual display is not simply “epigamic” (directed toward mate choice), but also effective in the arena of intra-sexual competition. Thus, when men compete for “air time” in an academic seminar, or “hang time” in a basketball court, they are not only attempting to impress the ladies, but also to out-shine other men … so as to be more attractive to the ladies.

The Mating Mind is full of unexpected treats. Just when the reader is convinced that the message has been gotten across, and he or she could readily fill in the remaining blanks, Miller comes up with another intriguing twist on his thesis. Don’t miss, for example, a truly hilarious imaginary monologue offered by a self-assessing male Satin Bowerbird (pg. 269-270). It alone is worth the price of the book, especially now that it is available in paperback.

Miller himself, not surprisingly, is a verbal virtuoso. Especially worthwhile is his argument that a pregnancy requires about a million words of linguistic foreplay (pp. 355-356), his analysis of the (otherwise unnecessary) verbal luxuriance of language itself which is difficult to interpret in other than sexually selected terms (pp. 369-370), and the well-documented fact that men typically dominate when it comes to public verbal displays, although Miller strikes just the right note of masculine humility when he readily acknowledges that “The fact that men often do not know what they are talking about only shows that the reach of their displays often exceeds their grasp” (pg. 377). This clearly doesn’t apply, however, to the versatile, powerful grasp of Geoffrey Miller himself.

A bit of personal disclosure: I’m heterosexual and happily married to boot. But if I weren’t, I’d find The Mating Mind not only intellectually fascinating, but a downright sexy display by the author … which itself should count as a vote for his thesis!

At the risk of concluding on a sour note, it is noteworthy that two such admirable efforts at understanding the adaptive value of the human brain should each ignore alternative hypotheses. Thus, Calvin barely acknowledges sexual selection, just as Miller gives at most a passing nod to survival selection. Although regrettable, such one-sidedness is understandable. Each author is attempting to call attention to a particular and heretofore insufficiently appreciated perspective, and probably for good reason: success in the academic world is more likely to accrue to people who associate themselves with a distinct point of view … even though the “correct” explanation is often associated with multiple, nuanced levels of causation. No matter; we want our explanations straight-forward and unitary.

For an interesting contrast, both Calvin and Miller take a stab at explaining the persistence and prominence of the seemingly inefficient hand-axe in the human archaeological/paleontological record. Calvin favors a variant of the “killer frisbee” hypothesis, whereas Miller sees in the hand-axe’s peculiar and seemingly self-defeating design evidence of a Zahavian handicap. My guess is that neither is correct, just as neither Calvin nor Miller captures all of the truth when it comes to human brain evolution. Nonetheless, I suspect strongly that each has glimpsed an important reality.

Even when the human brain gets to pondering itself and its remarkable capacities, it seems that those capacities - impressive as they are, and impressively as they are reflected in A Brain For all Seasons and The Mating Mind - remain beyond our ready grasp. Nonetheless, both Calvin and Miller enable the reader to experience the joy of reaching.

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© David P. Barash.

* Dr. Barash teaches, writes and does research at the University of Washington, in Seattle, where he has been in the psychology department since 1973. His work and interests are diverse: He was one of the early contributors to the growth of sociobiology, and he continues to conduct occasional field studies of animal behavior, especially the evolution and ecology of social systems among free-living animals, notably mountain-dwelling species such as marmots and pikas. At the same time, much of his attention has recently been directed to understanding the underlying evolutionary factors influencing human behavior, a discipline sometimes called "evolutionary psychology." And finally, since the early 1980s he has been active in researching, promoting, and practicing the field of Peace Studies. Dr. Barash feels that these issues - animal behavior, evolutionary psychology and Peace Studies - are fundamentally linked, especially since they all involve questions of how biology affects behavior, including male-female differences, reproductive strategies, and the troubling problem of violence in living things generally. Dr. Barash also has a long-standing interest in philosophical matters, notably Buddhism and existentialism, and their connection to each other and to the question of "life's meaning."


Barash, D. P. (2002). What's A Brain For? Human Nature Review. 2: 187-194.

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