Among life’s tradeoffs is whether to allocate resources (energy, food, risk, time) to pumping out as many offspring as possible and letting them fend for themselves or eking out fewer descendants and enhancing the chances of survival and reproduction of each one. The continuum represents the degree of parental investment expended by an organism.
Since parental investment is finite, investing organisms face a second tradeoff, between investing resources in a given offspring and conserving those resources to invest in its existing or potential siblings.
Because of the essential difference between the sexes—females produce fewer but more expensive gametes—the females of most species invest more in offspring than do the males, whose investment is often close to zero. Mammalian females in particular have opted for massive investment, starting with internal gestation and lactation. In some species, including Homo sapiens, the males may invest, too, though less than the females.
Natural selection favors the allocation of resources not just from parents to offspring but among genetic kin, such as siblings and cousins. Just as a gene that encourages a parent to invest in offspring will be favoring a copy of itself that sits inside those offspring, so a gene that encourages an organism to invest in a brother or cousin will, some proportion of the time, be helping a copy of itself and will be selected in proportion to the benefits conferred, the costs incurred, and the degree of genetic relatedness.
I’ve just reviewed the fundamental features of life on Earth (and possibly life everywhere), with the barest mention of contingent facts about our own species—only that we’re mammals with male parental investment. I’ll add a second: that we’re a brainy species that deals with life’s conundrums not just with fixed adaptations selected over evolutionary time but also with facultative adaptations (cognition, language, socialization) that we deploy in our lifetimes and whose products we share via culture.
From these deep principles about the nature of the evolutionary process, one can deduce a vast amount about the social life of our species. (Credit where it’s due: William Hamilton, George Williams, Robert Trivers, Donald Symons, Richard Alexander, Martin Daly, Margo Wilson.)
• Conflict is a part of the human condition. Notwithstanding religious myths of Eden, romantic images of noble savages, utopian dreams of perfect harmony, and gluey metaphors like attachment, bonding, and cohesion, human life is never free of friction. All societies have some degree of differential prestige and status, inequality of power and wealth, punishment, sexual regulations, sexual jealousy, hostility to other groups, and conflict within the group, including violence, rape, and homicide. Our cognitive and moral obsessions track these conflicts. There is a small number of plots in the world’s fiction, defined by adversaries (often murderous) and tragedies of kinship or love (or both). In the real world, our life stories are largely stories of conflict: the hurts, guilts, and rivalries inflicted by friends, relatives, and competitors.
• The main refuge from this conflict is the family—collections of individuals with an evolutionary interest in one another’s flourishing. Thus we find that traditional societies are organized around kinship and that political leaders, from great emperors to tinpot tyrants, seek to transfer power to their offspring. Extreme forms of altruism, such as donating an organ or making a risky loan, are typically offered to relatives, as are bequests of wealth after death—a major cause of economic inequality. Nepotism constantly threatens social institutions such as religions, governments, and businesses that compete with the instinctive bonds of family.
• Even families are not perfect havens from conflict, because the solidarity from shared genes must contend with competition over parental investment. Parents have to apportion their investment across all their children, born and unborn, with every offspring equally valuable (all else being equal). But while an offspring has an interest in its siblings’ welfare, since it shares half its genes with each full sib, it shares all of its genes with itself, so it has a disproportionate interest in its own welfare. The implicit conflict plays itself out throughout the life span: in postpartum depression, infanticide, cuteness, weaning, brattiness, tantrums, sibling rivalry, and struggles over inheritance.
• Sex is not entirely a pastime of mutual pleasure between consenting adults. That is because the different minimal parental investment of men and women translates into differences in their ultimate evolutionary interests. Men, but not women, can multiply their reproductive output with multiple partners. Men are more prone than women to infidelity. Women are more vulnerable than men to desertion. Sex therefore takes place in the shadow of exploitation, illegitimacy, jealousy, spousal abuse, cuckoldry, desertion, harassment, and rape.
• Love is not all you need, and does not make the world go round. Marriage does offer the couple the theoretical possibility of a perfect overlap of genetic interest, and hence an opportunity for the bliss we associate with romantic love, because their genetic fates are bound together in the same package—namely, their children. Unfortunately those interests can diverge because of infidelity, stepchildren, in-laws, or age differences—which are, not coincidentally, major sources of marital strife.
None of this implies that people are robots controlled by their genes, that complex traits are determined by single genes, that people may be morally excused for fighting, raping, or philandering, that people should try to have as many babies as possible, or that people are impervious to influences from their culture (to take some of the common misunderstandings of evolutionary explanations). What it does mean is that a large number of recurring forms of human conflict fall out of a small number of features of the process that made life possible.
THE FAURIE-RAYMOND HYPOTHESIS
JONATHAN GOTTSCHALL
Literary scholar; adjunct instructor, English Department, Washington & Jefferson College; author, The Storytelling Animal
I read about the Faurie-Raymond hypothesis a long time ago, but it didn’t click with me until I fought big Nick. Nick is a national guardsman who trains with me at the local mixed martial-arts academy. Technically we were just sparring, not fighting. But Nick is so strong, his punches so sincere, that even when he tries to throw gentle, he makes your consciousness wobble. The bell rang, and we engaged, and my fear passed quickly into disorientation. Something wasn’t right. Nick is powerful, but he’s not more skillful than I am and he’s not what you would call a graceful mover or a sophisticated striker. Nick plows forward: jab, cross; jab, cross, hook. Nick doesn’t bob. Nick doesn’t weave. Nick plows forward.
So why couldn’t I hit him? Why were my punches grazing harmlessly past his temples or glancing off his belly? And why, whenever I tried to slip and counter, was I eating glove leather? I tracked him through the blur of his hands, and all of the angles looked wrong, the planes of his face and body askew. There was nothing solid to hit. And all the while he was hammering me with punches I sensed too late—slow and heavy blows, maddeningly oblique.
When the bell finally saved me, we embraced (it’s a paradox; nothing makes men love each other as much as a good-natured fistfight). I collapsed in one of the folding chairs with my head throbbing and the sweat rolling down, and I said to myself, “That seals it. Faurie-Raymond has to be true.”
Nick represents a type that 90 percent of boxers fear and despise on sight. Nick is a lefty, which is, according to my pugilism professor, “an abomination” and “a birth defect.” Here, my professor joins other righty authorities in the sweet science, who don’t seem to be kidding when they say, “All southpaws should be drowned at birth.”
My professor’s claim that lefties are defective has a surprising grain of truth. In a world of scissors and schooldesks shaped for righties, being a lefty is not just annoying, it seems to be bad for you. According to a number of studies, lefties are at higher risk for disorders like schizophrenia, mental retardation, immune deficiency, epilepsy, learning disability, spinal deformity, hypertension, ADHD, alcoholism, and stuttering.
Whi
ch brings me to Charlotte Faurie and Michel Raymond, a pair of French scientists who study the evolution of handedness. Left-handedness is partly heritable and is associated with significant health risks. So why, they wondered, hadn’t natural selection trimmed it away? Were the costs of left-handedness canceled by hidden fitness benefits?
They noted that lefties have advantages in sports like baseball and fencing, where the competition is interactive, but not in sports like gymnastics or swimming, with no direct interaction. In the elite ranks of cricket, boxing, wrestling, tennis, baseball, and more, lefties are massively overrepresented. The reason is obvious: Since 90 percent of the world is right-handed, righties usually compete against one another. When they confront lefties, who do everything backwards, their brains reel, and the result can be as lopsided as my mauling by Nick. In contrast, lefties are used to facing righties; when two lefties face off, any confusion cancels out.
Faurie and Raymond made a mental leap. The lives of ancestral people were typically more violent than our own. Wouldn’t the lefty advantage in sports—including combat sports like boxing, wrestling, and fencing—have extended to fighting, whether with fists, clubs, or spears? Could the fitness benefits of fighting southpaw have offset the health costs associated with left-handedness? In 2005, they published a paper supporting their prediction of a strong correlation between violence and handedness in preindustrial societies: The more violent the society, the more lefties. The most violent society they sampled, the Eipo of highland New Guinea, was almost 30 percent southpaw.*
What makes a scientific explanation beautiful? General factors like parsimony play a role, but as with any aesthetic question, quirks of personal taste bulk large. Why do I find the Faurie-Raymond hypothesis attractive? Partly because it was an almost recklessly creative idea, and yet the data seemed to fit. But mainly because the undoubtable truth of it was pounded into my brain by a young soldier sometime last year.
This is not to say, with apologies to Keats, that beauty and truth are synonyms. Sometimes the truth turns out to be dull and flat. Many of the loveliest explanations—the ones we adore with almost parental fondness—turn out to be dead false. This is what T. H. Huxley called scientific tragedy, “the slaying of a beautiful hypothesis by an ugly fact.” Many studies have since examined the Faurie-Raymond hypothesis. Results have been mixed, but facts have surfaced that are, to my taste, quite decidedly ugly. A recent and impressive inquiry found no evidence that lefties are overrepresented among the Eipo of highland New Guinea.*
It hurts to surrender a beloved idea, one you just knew was true, one that was stamped into your mind by lived experience, not statistics. And I’m not yet ready to consign this one to the boneyard of lovely but dead science. Faurie and Raymond brought in sports data to shore up their main story about fighting. But I think the sports data may actually be the main story. Lefty genes may have survived more through southpaw success in play fights than in real fights—a possibility Faurie and Raymond acknowledge in a later paper.* Athletic contests are important across cultures. Around the world, sport is mainly a male preserve, and winners—from captains of football teams to traditional African wrestlers to Native American runners and lacrosse players—gain more than mere laurels: They elevate their cultural status; they win the admiration of men and the desire of women (research confirms the stereotype: Athletic men have more sexual success). This raises a broader possibility—that our species has been shaped more than we know by the survival of the sportiest.
GROUP POLARIZATION
DAVID G. MYERS
Professor of psychology, Hope College; author, Psychology, 10th edition
Forty-five years ago, some social-psychological experiments posed story problems that assessed people’s willingness to take risks: For example, what odds of success should a budding writer have in order to forgo her sure income and attempt writing a significant novel? To everyone’s amazement, group discussions led people to opt for more risk, setting off a wave of speculation about group risk-taking by juries, business boards, and the military. Alas, some other story problems surfaced in which group deliberation increased caution. (Should a young married parent with two children gamble his savings on a hot stock tip?) Out of this befuddlement—Does group interaction increase risk or caution?—there emerged a deeper principle of simple elegance: Group interaction tends to amplify people’s initial inclinations. This group polarization phenomenon was repeatedly confirmed. In one study, relatively prejudiced and unprejudiced students were grouped separately and asked to respond—before and after discussion—to racial dilemmas, such as a conflict over property rights versus open housing. Discussion with like-minded peers increased the attitude gap between the high-xand low-prejudiced groups.
Today, the self-segregation of kindred spirits is rife. With increased mobility, conservative communities attract conservatives and progressive communities attract progressives. Political journalist Bill Bishop and sociologist Robert Cushing report that the percentage of landslide counties—those voting 60 percent or more for one presidential candidate—nearly doubled between 1976 and 2008.* And when neighborhoods become political echo chambers, the consequence is increased polarization, as David Schkade of University of California–San Diego and colleagues demonstrated by assembling small groups of Coloradoans in liberal Boulder and conservative Colorado Springs. The community discussions of climate change, affirmative action, and same-sex unions diverged Boulder folks further leftward and Colorado Springs folks further rightward.
Terrorism is group polarization writ large. Virtually never does it erupt suddenly, as a solo personal act. Rather, terrorist impulses arise among people whose shared grievances bring them together. In isolation from moderating influences, group interaction becomes a social amplifier. The Internet accelerates opportunities for like-minded peacemakers and neo-Nazis, geeks and goths, conspiracy schemers, and cancer survivors to find and influence one another. When socially networked, birds of a feather find their shared interests, attitudes, and suspicions magnified.
Ergo, one elegant and socially significant explanation of diverse observations is simply this: opinion-segregation + conversation → polarization.
THE PRICE EQUATION
ARMAND MARIE LEROI
Professor of evolutionary developmental biology, Imperial College, London; author, Mutants: On Genetic Variety and the Human Body
Whenever we see highly ordered phenomena—a baby, a symphony, a scientific paper, a corporation, a government, a galaxy—we are driven to ask: How does that order arise? One answer, albeit an abstract one, is that each of these is the product of a variation-selection process. By this I mean any process that begins with many variants and in which most die (or are thrown into the wastepaper basket or dissipate or collapse), leaving only a few fit (or strong or appealing or stable) enough to survive. The production of organic forms by natural selection is, of course, the most famous example of such a process. It’s also now a commonplace that human culture is driven by an analogous process; but, as the above examples suggest, variation-selection processes can be seen everywhere, once we know what to look for.
Many others have had this idea, but none has seen its implications as deeply as George Price, an American living in London, who in 1970 published an equation describing variation-selection processes of all kinds.* The Price equation, as it is now known, is simple, deep, and elegant—my candidate explanation. It can be used to describe, inter alia, the tuning of an analog radio dial, chemical-reaction kinetics, the impact of neonatal mortality on the distribution of human birth weight, the reason we inhabit this universe out of the multitude we do not (assuming the others exist). But for me the real fascination of the Price equation lies not in the form he gave it in 1970 but in an extension he published two years later.*
One of the properties of variation-selection systems is that the selecting can happen at many different levels. Music is clearly the result of a variation-selection process. The composer sits at his piano consideri
ng what comes next and chooses one out of the world of possible notes, chords, or phrases that he might. Look at Beethoven’s manuscripts (Op. 47, the Kreutzer Sonata, is a good example)—they’re scrawled with his second thoughts. In 1996, Brian Eno wittily made this process explicit when he used SSEYO’s Koan software to produce an ever-varying collection of pieces that he called “generative music.”
But the music we have on our iPods is, of course, not merely the result of the composer’s selective choices—nor even those made by producers, performers, and so on—but ours. As individual consumers, we, too, are a selective and hence creative force. And we do not act only as individuals but also as members of social groups. Experiments show that if we know what music other people are listening to, we are quite ready to subsume (if not totally abandon) our own aesthetic preferences and follow the herd—a phenomenon that explains why it’s so hard to predict hits. So composers, consumers, and groups of consumers all shape the world of music. Umberto Eco made much the same point as long ago as 1962, in Opera Aperta (The Open Work). Of course, as a literary critic Eco could do no more than draw attention to the problem. But George Price solved it.
In 1972, Price extended his general variation-selection equation to allow for multilevel selection. This form of the equation has been useful to evolutionary biologists, allowing them to see, for example, the relationship between kin-and group-selection clearly and so put to rest endless controversies stemming from incompatible mathematical formulations. It hasn’t yet been applied to cultural evolution, though it surely will be. But the extended Price equation is much more important than even that. It slices one of the Gordian knots that scientists and philosophers of science have long wrestled with.
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