Darwin’s Other Idea

The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature
by Geoffrey Miller
New York: Random House, 2000

Darwinian evolution is seen as a cold, ruthless struggle for survival that shaped what we eventually became.  But, the critic responds, whence kindness, humor, language, playfulness, art and creativity?  Scientists have tried to explain altruism towards relatives as kin selection and other forms of morality as based on reciprocity, but we all often help people who are not related to us when there’s nothing to be gained.  Geoffrey Miller invokes sexual selection to fill the holes in human nature left unexplained by natural selection.

Reproduction Is as Important as Survival

In The Origin of Species Darwin devoted three pages to sexual selection.  In his second most famous book The Descent of Man, and Selection in Relation to Sex published twelve years later he devoted over 550 out of 900 pages to the idea.  What the scientist understood, and what those who followed him over the next century forgot, was that there were two main forces at work in evolution.  An organism needs to survive and reproduce.  A scrooge that stored up resources and survived just fine but had no interest in socializing with others or finding a mate might as well have died in infancy.  The herd could be culled through natural selection, the inability to survive in the environment, or through sexual selection, the inability to find a mate.  As long as our species is not strictly monogamous, and the vast majority of the time it hasn’t been, choice in romantic matters has helped shape evolution.

Before coming up with the theory, Darwin was confused by how wasteful nature tended to be.  He once told his son Francis that “The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!”  Why should such a thing evolve?  The peacock’s tail is by no means unique.  Across the animal kingdom, males seem to display ornaments that contribute nothing to or even take away from survival.  Some, like the male peacock’s tale, are connected to the body while others are an extended phenotype, something an animal creates.  During mating season, male bowerbirds of Australia and New Guinea spend almost every waking hour building elaborate nests.

Males of most species (of bowerbirds) decorate their bowers with mosses, ferns, orchids, snail shells, berries and bark.  They fly around searching for the most brilliantly colored natural objects, bring them back to their bowers, and arrange them in careful clusters of uniform color.  When the orchids and berries lose their color, the males replace them with fresh material.  Males often try to steal ornaments, especially blue feathers, from the bowers of other males.  They also try to destroy the bowers of rivals.  The strength to defend their delicate work is a precondition of their artistry.  Females appear to favor bowers that are sturdy, symmetrical, and well-ornamented with color.

The genetic ability to grow elaborate physical characteristics or drive to create art are usually found in the sex that competes for mates, i.e., males.  Miller hypothesizes that the human brain itself evolved to impress potential partners.  Not only did it help to deal with practical problems of survival, but a good sense of humor and the ability to make interesting conversation were themselves fitness indicators.  The brain, like the peacock’s tale, couldn’t grow and function properly in a diseased organism.  Thus, a healthy and complicated organ shows that an animal is relatively free of harmful mutations.

So why aren’t males significantly more intelligent than females?  Usually when a trait is sexually selected, in this case intelligence, nature ends up with a huge gender gap.  Part of the answer is that women needed to be able to detect mental fitness in males.  A woman would need to be intelligent enough to know when a male was using big words correctly or making logically consistent arguments.  Miller writes:

According to the widely used WAIS-R intelligence test, for example, English-speaking adult with an IQ of 80 typically know the words “fabric,” “enormous,” and “conceal,” but not the words “sentence,” “consume,” or “commerce.”  IQ 90 speakers typically know “sentence,” “consume,” and “commerce,” but not “designate,” “ponder,” or “reluctant.”  If you are flirting with someone, and they say they would like to “consume” your body in a passionate embrace, but they do not understand when you say you are “reluctant,” you can probably infer they have an IQ between 80 and 90.  We make these sorts of inferences quite automatically and unconsciously, of course.

Where we do see large gender differences is in ambition.  While women have evolved to appreciate art, in all cultures it’s men who mostly create it.

Another check that has kept men from becoming too much smarter than women has been monogamy.  The more polygamy there is in a species, the greater the gender dimorphism (sex differences).  In the polygamous gorillas for example, males are twice as heavy as females.  Humans are moderately dimorphic.  While men are less picky than women about their flings, when it comes to long term commitment the sexes are equally choosy.    Since males were to a certain extent selecting females too, the latter’s mind also evolved to be a fitness indicator.

Taking sexual selection into account explains all other kinds of seemingly inexplicable phenomena.  The average English speaker knows 60,000 words, but only 4,000 account for 98% of all conversation.  Basic English was created in the 1920s with only 850 words and is sufficient to express everything we can in natural English (albeit less efficiently).  So why do we know so many words?  So that friends and mates may be impressed when we use “azure” instead of blue.  As an African-American subject told a linguist,

Yo’ rap is your thing . . . like your personality.  Like you kin style on some dude by rappin’ better ‘n he do.   Show ‘im up.  Outdo him conversation-wise.  Or you can rap to a young lady, you tryin’ to impress her, catch her action-you know-get wid her sex-wise.

Language may have evolved to its complexity as a fitness indicator.  Prepubescent boys communicate just fine in grunts for all practical purposes.  Once language evolved, those who were more intelligent would’ve had more interesting things to say and introspection would’ve been selected for.

Ideals and Morality

Miller believes that, like art, the things we develop called morality, political philosophy, ideals and religion evolved through sexual selection.  As he points out, 99.9% of animal communication has nothing to do with truth content.  Among the few counterexamples are some chimp calls, bee dances, and (sometimes) human language.  Most communication exists solely to indicate fitness, like a frog’s mating call or the bowerbird’s nest.

Communicating truth can sometimes give us an advantage in terms of survival, but not in the competition for sexual success.  Imagine two cavemen getting into an argument about the purpose of the universe.

The hominid names Carl proposes: “We are mortal, fallible primates who survive on this fickly savanna only because we cluster in jealousy-ridden groups.  Everywhere we have ever traveled is just a tiny, random corner of a vast continent on an unimaginably huge sphere spinning in a vacuum.  The sphere has traveled billions and billions of times around a flaming ball of gas, which will eventually blow up to incinerate our empty, fossilized skulls.  I have discovered several compelling lines of evidence in support of these hypotheses . . .”

The hominid named Candide interrupts: “No, I believe we are immortal spirits gifted with these beautiful bodies because the great god Wug chose us as his favorite creatures.  Wug blessed us with this fertile paradise . . . Above the azure dome of the sky the smiling sun warms our hearts.  After we grow old . . . Wug will lift us from our bodies to join our friends to eat roasted gazelle and dance eternally.  I know these things because Wug picked me to receive this special wisdom in a dream last night.”

Which ideology do you suppose would prove more sexually attractive?

Muhammad and Brigham Young left behind more descendants than any scientist ever did.  We are a species that evolved to care about status, not truth.

People generally do things perceived as moral so people will have a positive opinion of them.  Not only is kindness attractive in a mate, but we can see how the evolution of ethics has worked by invoking the handicap principle.  In addition to the peacock’s tail being visually appealing, it makes surviving more difficult.  The male bird is saying “Not only does this nice tail show that I am mutation free, but I’ve been able to avoid predators will carrying this ridiculous thing around.”

The Israeli biologists Amotz and Avishag Zahavi in their book The Handicap Principle talk about a group of birds known as the Arabian babblers.  This species engages in competition to see who can be the most altruistic.  Dominant babblers won’t allow subordinate ones to take the risk of making the alarm call when a predator approaches.  The birds will try to shove food down the throats of non-relatives.  The Zahavis argue that the birds show their fitness by handicapping themselves.  Whether the disadvantage that the animal is trying to prove its fitness with is a physical appendage or an act, the principle is the same.

Excessive altruism in humans can work like this.  “I am so fit that I can afford to give millions to charity (or not worry about affirmative action helping those poor blacks, or whatever) and do it gladly.”   Ted Turner revealed that when he donated a billion dollars to the UN his wife Jane Fonda broke down and cried.  Aid organizations know that they can set off an arms race for donations by attracting a few rich donors.  Next time you see Angelina Jolie with her multiracial brood, you’ll understand why.

Those of us who rally against PC understand the frivolity of the beliefs of most people.  As Miller puts, it:

When individuals espouse ideological positions, we typically interpret their beliefs as signs of good or bad moral character. . . . Political correctness is one outcome of such attributions.  For example, if a scientist says, “I have evidence that human intelligence is genetically heritable,” that is usually misinterpreted as proclaiming, “I am a disagreeable psychopath unworthy of love.”  The arbiters of ideological correctness can create the impression that belief A must indicate personality trait X.  If X is considered sexually and socially repulsive, then belief A becomes taboo.  In this way our sexually selected instincts for moralistic self-advertisement become subverted into ideological dogmas.

He then adds that “I think that human rationality consists largely of separating intellectual arguments from personality attributions about moral character.”  Miller must understand that he’s a Darwinian rarity.

Sexual selection doesn’t care if what it favors is a good long term strategy.  The Irish elk evolved antlers so big that other functions of life, such as maybe reproduction, became impossible.  Any human population that adopts a maladaptive morality will move in a similar direction.

Evolutionary Psychology and Human Nature

The Mating Mind presents a much more colorful and interesting picture of evolution than what we’re used.  Our appreciation of music, art and oratory are just as natural and purposeful as our enjoyment of food and sex.  Miller hopes that Darwinism and evolutionary psychology will replace Freudianism, Marxism, and culturalism as the center of the humanities.  Truth will always remain as intellectual fads come and go.  If and when it does triumph in the human science, Geoffrey Miller’s theory of brain evolution may very well be a central part of the explanation of who we are.