Infidelity: Part of Nature’s Intelligent Design?

Infidelity: Part of Nature’s Intelligent Design?

Peter A. Hempel

In an article, “In Most Species, Faithfulness Is a Fantasy”, in the March 18, 2008 issue of The New York Times, science writer Natalie Angier notes the widespread incidence of cheating among all kinds of animal species:

Assay the kids in a given brood, whether of birds, voles, lesser apes, foxes or any other pair-bonding species, and anywhere from 10 to 70 percent will prove to have been sired by somebody other than the resident male…

Many other authors have documented this phenomenon as well. It’s hardly an accident that our art and literature, our operas and our country western songs, are filled with tales of cheating, forbidden love, and jealous rages. In its famous Index of factoids, Harper's Magazine notes:

Chance that a romance cited by People magazine in 1966 as among the century’s “greatest love stories” was adulterous: 1 in 2

Nevertheless, while Angier’s article describes the surprisingly widespread incidence of cheating, she stops short of considering its evolutionary implications as a model for genetic competition and selection.

On the one hand, one could argue that polygyny (one man with multiple wives) is the obvious model for increasing the genetic productivity of the highest status males. And, as Robert Wright points out in The Moral Animal, this winner-take-more arrangement creates a musical-chairs chain of scarcity which makes the overall competition for females more intense than ever, and ups the genetic stakes all around.

One Bill Gates, for example, could afford to take as wives a thousand highly desirable women with a none too shabby $10 million pre-nup for each without making too severe a dent in his wallet, leaving the rest of the women in the pool that much more valuable to the remaining males. Furthermore, polygyny joins the genes of high-status males with those of highly attractive (desirable) women as well – a win-win scenario on both sides.

Of course, working night and day (I’m giving him two women a day, no point in being unrealistic here) it would take Bill nearly a year and a half – no weekends off – to complete the rounds. And even for $10 million, some women might not consider this a satisfactory (or satisfying) deal. (Judging by his reputation as a hardliner in his business dealings, I’m quite sure Bill would not be interested in supporting wifely activities on the side with other males.)

Polygyny leaves two other problems as well as a method of genetic competition. While some wealthy males may indeed be self-made (as with Bill Gates or the perhaps sexier Steve Jobs), many more (like Saddam’s late sons Uday and Qusay, for example) merely inherit their status and wealth, and may indeed be quite retrograde from a genetic (or at least moral) point of view.

Moreover, even if this issue were addressed, we would still face one more problem: a significant portion of males in the society would end up wifeless and childless, and however modest their income, they would be contributing nothing directly to the overall societal burden of supporting and nurturing children. (In Mormon polygynous societies, they solve this problem by banishing unattached males, but that only displaces the issue rather than solving it.) Instead, many children would receive only fractional fatherly attention and guidance – a lack that even large sums of money cannot fully compensate for.

I don't know about the outcome for discarded Mormon males, but in the Middle East, the implications are clear:

In a 2011 doctoral thesis, anthropologist Kyle R. Gibson reviewed three studies documenting 1,208 suicide attacks from 1981 to 2007 and found that countries with higher polygyny rates correlated with greater production of suicide terrorists.^[55][56] Political scientist Robert Pape has found that among Islamic suicide terrorists, 97 percent were unmarried and 84 percent were male (or if excluding the Kurdistan Workers' Party, 91 percent male),^[57] while a study conducted by the U.S. military in Iraq in 2008 found that suicide bombers were almost always single men without children aged 18 to 30 (with a mean age of 22), and were typically students or employed in blue-collar occupations.^[58] In addition to noting that countries where polygyny is widely practiced tend to have higher homicide rates and rates of rape, political scientists Valerie M. Hudson and Bradley Thayer have argued that because Islam is the only major religious tradition where polygyny is still largely condoned, the higher degrees of marital inequality in Islamic countries than most of the world causes them to have larger populations susceptible to suicide terrorism, and that promises of harems of virgins for martyrdom serves as a mechanism to mitigate in-group conflict within Islamic countries between alpha and non-alpha males by bringing esteem to the latter's families and redirecting their violence towards out-groups.^{[59] (Wikipedia)}

In any case, whatever the merits of polygamy (to cast the net more widely), pair-bonding has established itself as the norm in many species, and in a large majority of human societies as well.

So let us consider (although our society today is more fragmented than the world of Leave It to Beaver) a society where married couples and stable homes are the norm. Faithful couples reproducing at replacement levels will largely simply maintain the overall genetic status quo. If each couple remains monogamous, the only way to compete genetically is to have more children – which presents an overpopulation challenge and leaves each child within the household with a reduced share of family resources and parental attention.

But that is not the end-point of the evolutionary model.

As Angier notes, while many species form mating pairs, infidelity is widely practiced among virtually all species, although partners on both sides of the sexual aisle make strenuous (but often ineffectual) efforts to keep their mates from straying.

Overall outcomes suggest that, whether through formal polygamy or through infidelity, successful males punch above their weight in paternity:

Some studies of mitochondrial DNA have shown that there have been more mothers than fathers in the genetic record of the human species, meaning that the proportion of females that have reproduced in each generation has generally been greater than the proportion of men that reproduced. (Wikipedia)

Nature itself is hardly supportive of fidelity; as Wright as well as other authors note, married or not, women who are ovulating send off a variety of signals to all available males – they dress in sexier outfits and wear more make-up, and indeed the majority of infidelities occur around the time of ovulation. (One male response to this threat is the anti-fashion body-hiding burqa – which covers even a woman’s eyes – and draconian social strictures in many Middle Eastern countries; an even worse response is the practice in some Muslim societies of female sexual mutilation, including clitorectomy, to suppress the female sex drive.)

The importance of passing on one's own genes can be seen in the vast sums of money that infertile couples spend to try to have their own children, even while vast numbers of other babies remain waiting to be adopted. But evolutionary dynamics (among all species) operate on a far larger canvas than the (equally evolutionarily) understandable wishes of individuals.

If we look at the situation from a species-level perspective, infidelity offers a chance for genetic competition to carry on in the most advantageous way.

First of all, infidelity is less affected by considerations of wealth per se (which can simply be inherited) than marriage is and more affected by considerations related to raw genetic desirability: good looks, athleticism, and talent (musicians, artists, pro athletes, best-selling authors, attractive friends of the husband) can serve as much more compelling attributes for that exciting (or even dangerous) liaison than mansions or seven-figure IRAs. Even the dangers involved in adulterous coupling could be viewed as raising the genetic bar. Would a woman risk her marriage and security for second-rate genes? Would a wimp of a man be prepared to risk his own marriage, and the potentially lethal wrath of a wronged husband?

Secondly, the offspring of such a dalliance (if undetected) is likely to grow up in a warm, loving and stable home, with a pair of attentive and devoted parents. Meanwhile, the merely dull will play out the role for which they are best suited, the care and tending of the offspring of the best and the brightest.

The interesting question now is how the availability of DNA testing will impact this scenario. The intrusion of scientific technology into the dance of the sexes is no small issue. The pill represented the first time in the entire history of our species that fertile females were able to completely decouple sex from reproduction, and it led directly to a sexual revolution on a scale never imagined before. Since then, of course, the advent of AIDS has put something of a damper of the Brave New World playbook of fun sex anytime, with anyone. Where might US society be today if AIDS hadn’t arrived to spoil the party? Why bother with marriage at all?

In some societies, especially in northern European countries where socialized safety nets have greatly reduced women’s dependence on a mate’s income, marriage has declined dramatically. In our country, marriage rates have declined, but after a sharply rising divorce rate for a while among all groups, marriage has made a comeback as a part of the better life; in a recent column David Brooks included marriage as a key element in the class divide:

…the educated and uneducated lead different sorts of lives. Educated people are not only growing richer than less-educated people, but their lifestyles are diverging as well. A generation ago, educated families and less-educated families looked the same, but now high school graduates divorce at twice the rate of college graduates. High school grads are much more likely to have kids out of wedlock. High school grads are much more likely to be obese. They’re much more likely to smoke and to die younger.

Along the same lines, Emily Yoffe, who writes the “Dear Prudence” column (an Ann Landers-style advice column) for Slate.com, in an article decrying the fuzzy glow that Juno shines around unwed pregnancy, argues the critical importance of marriage itself for raising children:

…modern culture is out of touch with the needs of children. Some researchers identify out-of-wedlock births as the chief cause for the increasing stratification and inequality of American life, the first step that casts children into an ever more rigid caste system. Studies have found that children born to single mothers are vastly more likely to be poor, have behavioral and psychological problems, drop out of high school, and themselves go on to have out-of-wedlock children.

… Scholar Kay Hymowitz, author of Marriage and Caste in America: Separate and Unequal Families in a Post-Marital Age…explains that…a solid marriage…is a formula "needed for upward mobility, qualities all the more important in a tough new knowledge economy."

All of which would go back to support the idea that infidelity within a “monogamous” society (unless DNA testing screws things up) offers the best opportunity for differential gene selection to be paired with the benefits of a stable home life.

An interesting additional twist is that this “monogamous” relationship is heavily weighted to the genetic benefit of women. If the husband simply cheats and impregnates another woman who is married to someone else, the original wife is not left taking care of or wasting resources on anyone else’s offspring.

The husband, on the other hand, has no such guarantees – barring clear evidence of misbehavior, he is contracted to care for the children his wife bears, regardless of their origin. There is a long tradition of women being more insistent on marriage, while men get cold feet, refer to marriage as the old ball and chain, etc. Maybe that’s not just sexism, maybe it’s logic. And for all those men out there who want to have sons to pass on the family name – if you want to be sure of passing on the family genes, go for daughters instead.

Many people and institutions prefer to deny this massive rule-bending and bed-hopping reality or rail against it – cf. for example, John Hagee (the right-wing preacher who endorsed McCain):

Christians don't steal or lie, they don't get divorced or have abortions. If the Ten Commandments were followed by everyone we would be able to fire half the police force and in six months the prisons would be all half empty.

Nature, however, begs to differ. It’s almost as if evolution was guiding our paths with an invisible hand – its own Intelligent Design, if you will.

Peter A. Hempel, Ph.D.

Princeton, NJ

03-22-08 (updated: 05/11/26)

peterahempel@gmail.com