by Jesse James
For example, how and why did females evolve a preference for the male peacock’s gaudy tail when it clearly hurts its chances of survival? Peacocks with big, bright tails are likely to end up on the dinner plate of some hungry jungle cat or stray dog. Why don’t female peacocks prefer some less astonishing male who might live to a ripe old age? Darwin had no idea.
Enter Sir Ronald Fisher, a brilliant young British mathematician and evolutionary biologist. Fisher’s insight was that female sexual preference, just like male ornamentation, required an evolutionary explanation – preferably an adaptive one. In what became known as the ‘sexy son’ theory of female mate preference, Fisher argued that ‘sexy’ traits are desirable precisely because other females find them desirable. A peacock’s tail is bright and pretty but serves no evolutionary purpose. Peahens find it sexy only because other peahens find it sexy.
Richard Dawkins notes that ‘any individual, of either sex, is likely to contain both genes for making males have a certain quality, and genes for making females prefer that selfsame quality, whatever that quality might be.‘9 In other words, we look for attractive mates because we want our offspring to be attractive too. We want to make ‘sexy sons.’
Fine. But Fisher recognized that certain ‘sexy’ traits, like the peacock’s tail, negatively impact survival. This was about as far from natural selection as you could go. Why would females prefer males who are less likely to survive?
The short answer is that males and females get stuck on an ‘evolutionary treadmill’ in which stepping off the treadmill means leaping into genetic oblivion. If most peahens prefer peacocks with cumbersome tails, then any peahen that deviates from this preference would make fewer babies. A peahen that mates with a short-tailed peacock will produce sons with short tails. Her sons would be less attractive to the majority of peahens, leaving fewer descendents.
Whew, that’s some logic. If you’re a philosopher, the knives are already out.
Sir Ronald’s argument assumes what it is trying to prove, namely that if females choose, then it pays to choose, but why choose a trait with negative survival value at all? Instead of choosing a sexy tail, why not prefer bigger teeth, stronger leg muscles, or some other trait which actually helps the animal survive? Why pick a maladaptive, gaudy and useless tail as your sexual preference?
The argument is also kind of circular; what came first, the female preference for long tails or the long tails?
Fisher was no dummy. Aware of the logical conundrum, he theorized that females must be choosing characteristics during the initial stage of the process that genuinely enhance survival, but the evolutionary treadmill sometimes becomes a runaway train, unable to stop, resulting in maladaptive physical traits like the peacock’s tail. No individual female can afford to step off the evolutionary treadmill.10
Aware of the problems plaguing the ‘sexy son’ theory, evolutionary biologists sought a more logically consistent explanation of female sexual preference.
In what became known as the ‘good genes’ theory (also called the he-man theory), scientists speculated that animals are attracted to members of the opposite sex representing high reproductive and genetic potential. Proposed by W.D. Hamilton and Marlene Zuk in the early 1980s, the ‘good genes’ theory argues that females choose males with traits indicative of good genes which will increase the survival or reproductive capacity of their offspring.
Peahens prefer males with beautiful tails because beauty suggests good genetic qualities such as vigor, disease resistance, and strength. Females want to ‘buy’ these qualities for their children.
Peacocks have it easy compared to the bower bird. Female bower birds require their suitors to build gigantic, utterly profligate nests for them – in the mere hope of getting laid. And the male birds do it, year after year, for the chance to monopolize a female sexual resource. Courtship and mating occur in the bower, while females nest and rear their young in the trees. Jared Diamond describes his first encounter with a bower nest in the jungle:
‘Suddenly, in the jungle, I came across a beautifully woven circular hut eight feet in diameter and four feet high, with a doorway large enough for a child to enter and sit inside. In front of the hut was a lawn of green moss, clean of debris except for hundreds of natural objects of various colors that had obviously been placed there intentionally as decorations. They mainly consisted of flowers and fruits and leaves, but also some butterfly wings and fungi. Objects of similar color were grouped together, such as red fruits next to a group of red leaves. The largest decorations were a tall pile of black fungi facing the door, with another pile of orange fungi a few yards further from the door. All the blue objects were grouped inside the hut, red ones outside, and yellow, purple, black and a few green ones in other locations.’11
Bower construction displays skill and craftsmanship, suggesting good genes. Useless for nesting, the love-shack is abandoned once the business of reproduction is finished. Females cruise the bower displays, carefully inspecting the male bird’s workmanship, an indicator of his genetic worth. A similar scene occurs every Saturday night on the Hollywood strip.
In the Red Queen, Matt Ridley explains that ‘if you spot somebody with good genes, it is your inherited habit to buy some of those genes … people are attracted to people of high reproductive and genetic potential – the healthy, the fit, and the powerful.’ Good genes are a good bet.12
Fisher, Dawkins and others had resolved many of the questions that Darwin left unanswered, but there was one final piece of the puzzle missing. How would animals signal good genes without being copied by false pretenders?
Chapter 2
Beauty & The Beast
‘Cosmetic baby, plug into me
And never, ever find another.
And I realize no one’s wise
To my plastic fantastic lover.’
– Jefferson Airplane
Some animals make Bernie Madoff look like the Pope.
The animal kingdom is rife with fraud and forgery. Harmless snakes evolve colors which mimic poisonous ones. Certain insects develop coloring and flight patterns to impersonate stinging bees. If signs of genetic fitness could be easily forged, animals would certainly evolve ways to fake them. Indicators of fitness must incur high marginal costs in order to be reliable, or else a weak pretender could easily swoon mates away from a high-fitness real McCoy. Fitness indicators therefore create genuine handicaps to the individual. The tail of a peacock, or the mane of a lion, or the bowerbird of a bower, simply cannot be faked. They cost real energy to produce. They incur real costs and risks.
Fitness indicators can be thought of as ‘truth in advertising’ for animals. Unlike traits produced through natural selection, which increase the survivability of an individual organism, fitness indicators advertise differences in heritable fitness between individuals. The remarkable and indeed revolutionary idea was that certain traits, which were harmful to the overall fitness of the organism, evolved through sexual selection as barometers of the animal’s genetic quality in order to attract mates.13
Why do we find certain human traits ‘sexy’ and others unappealing? Evolutionary biologists think they’ve found the answer.
Israeli biologist Amotz Zahavi conducted impressive research into fitness indicators in both the animal and human world, dubbing the subject ‘The Theory of Honest Signals,’ sometimes called ‘handicap theory.’ Zahavi realized that individuals with low fitness cannot grow their bodies or brains with sufficient precision to display high quality ornaments. Animals with higher mutation loads develop less symmetric bodies and ornaments. Weaker individuals cannot afford the luxury of high-cost fitness indicators because they must allocate most of their energy and resources to basic survival needs.14 In other words, a low-fitness lion can’t afford to grow a large, sexy mane just to look good. More important things – like eating or fighting off disease – consume his limited energy resources. Jared Diamond points out that ‘a signal that entails no cost lends itself to cheating
, since even a slow or inferior animal can afford to give the signal. Only costly or deleterious signals are guarantees of honesty.’15
Handicaps succeed as fitness indicators precisely because they are handicaps. The more vulnerable they are to disruption by poor nutrition, parasites, injury, inbreeding, mutation load or pathogens, the more useful they are as fitness indicators. Geoffrey Miller explains that the value of an individual’s ‘handicap’ as an honest signal increases with its degree of burden to the individual’s survival. Miller points out that ‘Handicaps have the counter-intuitive feature that the more vulnerable they are to disruption by poor nutrition, injury, parasites, pathogens, genetic inbreeding, high mutation load, or socially subordinate status, the more useful they are as fitness indicators.’16
Fitness indicators tend to be complex and costly displays, difficult to grow and maintain, potentially detrimental to the survival of the organism. Only the strongest, genetically-blessed individuals in a species can afford to display the most impressive fitness indicators. It is precisely their costliness and risk that makes them valuable as indicators of high fitness. Unlike natural selection, the process of sexual selection doesn’t produce a better animal, just a more honest one.
Writers get a lot of mileage out of the peacock’s tail. We’ve already discussed how it slows down the male peacock, attracting predators. Even worse, peacocks expend tremendous energy to produce the intricate design and bright coloring of their ornament. Such energy could have been invested in gathering food, searching for mates, building a nest, or evading predators – but instead it is ‘wasted’ on a gaudy, profligate tail. But the tail has one overwhelmingly important function – it communicates to female peacocks that the male is so strong, so virile, that he can afford to waste most of his energy on producing a functionally useless display. His tail indicates high fitness. The female wants his good genes for her offspring. However wasteful, the tail is sexy.
Consider bird songs, which attract unwanted attention from birds of prey, thereby harming the individual survival chances of the organism. Presumably only a strong, fast or intelligent songbird could afford to attract the attention of falcons by crowing love songs for the opposite sex. Females tend to reward boldness with sexual favors, regardless of whether the boldness emerges from behavior, as in the case of songbirds, or purely physical displays such as the peacock’s tail. Jared Diamond explains that ‘The female who selects such a male is like the medieval damsel testing her knight suitors by watching them slay dragons. When she sees a one-armed knight who can still slay a dragon, she knows that she has finally found a knight with great genes. And that knight, by flaunting his handicap, is actually flaunting his superiority.’17
When a herd of gazelles spots a lion, the strongest members of the herd will ‘stot,’ a process of jumping up and down to draw attention to themselves. Now this might seem like an odd thing to do when you encounter a lion. Personally, I would prefer to hide in the middle of the pack, and draw as little attention to myself as possible. But here evolutionary logic trumps my meager attempt at reason. Stotting communicates to the lion which members of the herd are the strongest and fastest. If you’re a lion, would you chase the Michael Johnson of gazelles? Or would you prefer to go after the low-hanging fruit, targeting some apparent weakling cowering from your sight? By drawing attention to themselves, the strong members of the herd who are ‘stotting’ are really saying ‘look here, Mr. Lion, I’m strong and fast, so fast that I can afford to show off without any fear. You might as well go after some other gazelle, because you’ll waste your time chasing me.’
According to Zahavi, stotting advertises to the predator (usually a big, mean, hungry lion) that certain gazelles are high fitness individuals and that chasing them would be a waste of time and energy.18
Stotting seems to mimic the words of The Godfather: ‘I don’t like violence, Tom. I’m a businessman. Blood is a big expense.’
Healthy gazelles and lions both gain evolutionary benefits by avoiding a chase because fruitless pursuit costs energy without providing benefits to either of them. How could healthy gazelles advertise their fitness? If they simply changed color, or batted their hooves on the ground, unhealthy gazelles could evolve to mimic their behavior. Absent an honest signal to the lions, the adaptation would confer no evolutionary advantage. It wouldn’t work.
Low-fitness gazelles cannot imitate stotting because the lion would quickly catch up to eat them. Since only high-fitness gazelles can afford to stot, it serves as an honest signal to lions to look elsewhere for their evening meal.
As Richard Dawkins explains in The Selfish Gene, ‘an individual who jumps high is advertising, in an exaggerated way, the fact that he is neither old nor unhealthy. According to this theory, the display is far from altruistic. If anything it is selfish, since its object is to persuade the predator to chase somebody else.’19
And yet stotting may be even more subtle than that. Healthy gazelles gain a natural selection advantage by discouraging the lion from pursuit, but they also obtain an edge in sexual selection within the herd by their ostentatious display of fitness. The females in the herd are not blind. Facing the threat of a lion, there can be little doubt which males exhibit high fitness traits. By the ruthless logic of evolution, the males who jump the highest must have the best genes, becoming the most attractive to the females.
Enough talk about gazelles and peacocks. We’re interested in men and women. Once you understand handicap theory, you notice fitness indicators everywhere in your daily life.
The Human Peacock
In the 1950s and 60s, one icon of male sexuality was the ‘Marlboro Man,’ a rough-and-tumble looking cowboy-type brandishing a Marlboro cigarette. What made this guy so sexy? It certainly had something to do with the cigarette. In almost all cultures throughout the world, and despite millions of dollars in advertising campaigns warning about nicotine health risks, young people still think it’s cool to light up. Smoking is sexy even though we know cigarettes cause cancer. Or is it sexy because they cause cancer?
Perhaps you have already guessed the punch line. Smoking is an ‘honest signal’ of genetic fitness.
Zahavi would argue that smokers accept a genuine handicap; cigarettes expose us to dangerous chemicals, depress our immune systems, decrease our aerobic ability, and, of course, cause lung cancer. An individual who voluntarily embraces such a handicap and survives (at least long enough to reproduce) must have good genes. The Marlboro man was sexy because he displayed an honest signal of fitness.
Nobody knows when our ancestors, cold and hungry, took their first sips of beer or moonshine. Like most inventions in human history, fermentation was probably the result of a fortuitous accident which occurred tens of thousands of years ago. We know from the discovery of beer mugs in the late Stone Age period that a Bud Light prototype existed as early as the Neolithic period, roughly 10,000 B.C.20
According to the Old Testament, Noah planted a vineyard on Mt. Ararat in present-day Turkey. Apparently he wanted some fine Merlot to ease the boredom on his Ark during the Flood. Or maybe he was looking for love.
Although Noah might not have been consciously broadcasting his genetic prowess, alcohol is another example of a human fitness indicator. Liquor offers no nutritional value whatsoever – in fact it is straight poison. Even in low quantities alcohol wrecks havoc on the liver and kidneys. Yet alcohol consumption dates back tens of thousands of years. Restaurants bribe local government officials with huge sums of money for a liquor license to intoxicate their customers. A young man who refuses to poison himself with alcohol at a party or rave faces ostracism and abuse; whispers of ‘loser’ percolate around the room. Like smoking, young people consider alcohol consumption almost universally sexy. Keg parties are so common in university as to be generally accepted by the administration, even when drunken undergraduates stumble helplessly across campus on Sunday morning.
Why is alcohol sexy? Precisely because it is dangerous. Precisely because it impo
ses a handicap. Drinking alcohol advertises the superiority of your genes; ‘Look at me, I can drink this poison and still survive.’ Jack Daniels never had it so good. 21
‘Ten thousand years ago, we “displayed” by challenging a lion or a tribal enemy. Today, we do it in other ways, such as by fast driving or by consuming dangerous drugs,’ explained Jared Diamond in The Third Chimpanzee.
My girlfriend likes the song “Just Dance” by Lady Gaga. She sings about having too much to drink, losing her keys, her phone and not knowing where she is. ‘Just dance’ though, it’s all going to be OK. Apparently men find women in a drunken fog irresistibly sexy. Dr. Laina Y. Bay-Cheng notes that women in these images are not merely passive sexual objects for male attraction, but are actively promoting a sexy image to young girls connected with alcohol, drug use and smoking. They are teaching young women how to be sexy and attract males by smoking and otherwise doing harm to their bodies. ‘Women are singing to women about the fun that can be had if you get really drunk and go out … part of the allure and what we have to reckon with is that it actually could look like a lot of fun,’ said Bay-Cheng. What is so sexy about drinking poison or inhaling black tar? Good genes.22
Skeptics will argue that humans drink and smoke because it makes them feel good. This is true, of course, as far as it goes; but it doesn’t go very far. Enjoying an activity doesn’t explain why it would be viewed as sexy. I eat chocolate pie every night because it is sweet and sugary, but my girlfriend does not find me any sexier with a smudge of chocolate on my lips. Activities that incur costs and risks are sexy because they impose a handicap. I would guess that many more people play golf than American football, but would you bet that professional golfers get laid more often than football quarterbacks?
