odern feminism’s leading thinkers believe their core project is to expose the ancient “myths” that guide our thinking about men, women, and families. In The Second Sex (1949) Simone de Beauvoir identified the “feminine myth” that women and men have different dispositions. Betty Friedan applied Beauvoir’s insights to America in The Feminine Mystique (1963). Since then, Naomi Wolf’s The Beauty Myth (1990) has contended that ideals of feminine beauty exist mostly to keep women in their place. The Frailty Myth (2000), by Colette Dowling, debunked the idea that women are weaker, slower, and less competitive than men, and Martha Fineman ripped the veil from The Autonomy Myth (2004). She called for abolishing marriage and replacing it with state support for dependents.

Exposing myths entails stripping away unchallenged ideas and deceptive surfaces to reveal the true causes that shape human destiny, and the real freedom people have in fashioning their identities. For feminists, differences between the sexes, and the importance of monogamous, enduring, exclusive marriage, are the most fundamental, pernicious myths. Sex differences, seemingly obvious and universal are, they contend, merely social constructs. People suffer not just myths about gender but Delusions of Gender (2010), Cordelia Fine argues. Men and women are at bottom autonomous, with limitless freedom to make their identities however they want. The only limits placed on humans are artificial ones that deserve to be disregarded and altered.

It is true that how a society imagines manhood and womanhood—gender—imparts different expectations and virtues for members of each sex. And it’s also true that understandings of gender have varied in different eras and locations. That gender has been flexible, however, does not mean it should be considered infinitely flexible. Sex and gender inform each other, which means that sexual difference is neither determinative nor simply mythical. Sexual differences are factual, a truth located on the surface, not beneath it.

Furthermore, myths have value. We could not sustain human life without parents’ pleasing myth that their children are special, deserving a greater investment than others. And as George Bernard Shaw is said to have asserted, romantic love itself requires exaggerating the difference between one person and all others.

The idea that bearing and nurturing children is central to marriage has been dismissed as a myth or prejudice in court opinions about same-sex marriage, which treat marriage as just one more contractual arrangement between consenting adults. In addition, David P. Barash and Judith Eve Lipton—husband and wife, quaintly enough—wrote in The Myth of Monogamy (2001) that monogamy is rare among animals, which means we shouldn’t expect fidelity among human beings. Barash, an evolutionary biologist and psychology professor at the University of Washington, has a new myth-busting book, Out of Eden, about our polygamous human pre-history and its consequences for society and for individual character.  

Barash, like other evolutionists, argues that stubborn genetic realities limit how much society can reconstruct its ideas of gender. Sex differences, in particular, appear intractable in all societies, and largely impervious to efforts to reconstruct nature. For Barash, many of the most prominent sex differences we observe cross-culturally arise because human beings have a promiscuous or polygamous past. Other conventions that exist today on the surface of things—such as monogamy—may be less firmly connected to genetic biology and thus may whither. Sex differences seem intractable, while marriage institutions seem changeable. How should people committed to overcoming nature approach the intractable?

“Evolution,” Barash contends, “requires us to get over the illusion…that we are in still, in some inchoate way, SPECIAL.” By discarding this illusion he identifies the basis of sexual differences in animals across the kingdom, and in political communities across the globe. We can discover the human through investigating the non-human.

Males and females define “reproductive success” differently. This difference accounts for much observable sexual difference even today. For males, reproductive success comes from spreading one’s seed widely and ensuring that one’s own genes survive. Males stave off other males to gain access to females and protect that access once they have it gained. As a result, bigger, stronger, more jealous, more violent tendencies tend to survive in the male. For females, reproductive success means getting good genes from a successful male, then inducing him to stick around to provide protection so their offspring survive. Natural selection, therefore, favors different tendencies in women: more nurturing, and less inclined to pursue multiple partners, at least overtly. Males and females are each aggressive in promoting their reproductive interests, but aggressive in different ways.  

According to Barash, male humans are about 20% larger and stronger than female humans, because the strongest males have survived to pass on their genes. Strength came into play first because males fought with one another for sexual access. The strongest won, and this victory secured them multiple partners. Strength also came in handy because this small community needed to protect those women from competitors, predators, and other depredations of chance. From this “ghost of polygamy” comes the male’s greater penchant for violence and aggression, universally observed. The aggressive and strong have survived to pass on their genes, while weaker, less aggressive males have lost the battle to perpetuate their genetic traits.  

Reproductive fitness also explains what Barash calls the “near-universal double standard” about sexual fidelity. Males and females are both concerned to perpetuate their own genes. A woman knows that a child is hers, but a man needs the guarantee provided by female monogamy to justify protecting and rearing particular children. The standard is a cultural construction to be sure, but is constructed in the evolutionary interests of the species. Females learn to navigate this cultural norm shrewdly, while also becoming nurturing, caring, and seductive as they perpetuate their genes.  

Most animals and most cultures are, according to Barash, polygamous. The “ghosts of polygamy” survives in our genes. Western peoples, especially, have embraced monogamy. Polygamy leads to a war within and between the sexes, while monogamy leads to “shared interests,” “male-female equality and mutual flourishing.” The arc of biological and cultural evolution bends toward monogamy.  

Evolutionary theory sounds conservative, then, defending the inescapable and workable against the modern penchant to resist or simply deny nature. Nevertheless, Barash is like many left-wing Darwinians in believing that evolution, rightly understood, allows for, or even favors, a permissive sexual morality. He worries that “right-wing ideologues” will seize upon his findings and advocate for “government programs that ‘enhance marriage,’ ‘contribute to supporting the pair-bond’ or whatever it takes to sustain a long-term, heterosexual monogamous relationship as the best…way to rear healthy, happy, socially responsible children.” Indeed, more than a few pro-family, Darwinian thinkers—including David Popenoe, Steven Rhoads, George Gilder, and others—have advanced such ideas.  

Barash, however, embraces a post-genetic future, a “more expansive view” that “opens the door to accepting, encouraging, and otherwise supporting child care programs and systems that don’t necessarily require traditional monogamous, heterosexual marriage, or indeed, marriage of any sort.” That we know nature to favor the survival of the fittest means that we can do something about it and, perhaps, conquer such nature in the name of greater human creativity. “[R]ising above our human nature may be just what is needed,” Barash writes. The social stability his argument derives from evolutionary theory is negated by his liberalism.  

The practical implications of Barashian evolutionary theory are only the beginning of its problems. Its greatest failure lies in stripping away the moral reality of human life. Human beings come together not only to live but to live well. Through marriage and family life, men and women seek to live honorably and admirably. Humans need reasons to believe that survival is worth the effort. Darwinism explains the human in light of the animal, but cannot account for humans’ unique concerns and capacities as political animals possessing reason and speech.  

Political communities do indeed construct different images of gender as a means of aspiring to these higher things. Monogamous marriage is but one of the institutions that have arisen to register the facts of life, tame the penchants of the two sexes, and respond to the human aspiration for nobility. Other institutions may deal with the greater male tendency for violence and aggression and the female’s connection with her child and children.

Reason, according to some Darwinists, is a reflection of a “mating mind”—an evolutionary adaptation to maximize reproductive fitness. Barash’s Darwinism cannot, however, explain why we should respect human limits. Birds, bees, and educated fleas do it, after all—for the same reason human beings do it. But marriage and family life concern the meaning of love and its rank as a human good. Yet, unlike these animals, human beings infuse all that they do with the aspiration for meaning and purpose. And neither birds, bees, nor educated fleas do that.