The Evolution of Marriage
From the May 19, 2014, issue of NR



‘A girl for every boy, a boy for every girl”: That’s the main thesis of William Tucker’s engaging new book. With polygamy, you see, there isn’t a girl for every boy, and the leftover boys must find some other — usually disruptive and frequently violent — way to pass their time. But the “unique social contract of monogamy — a male for every female, a female for every male — lowers the temperature of sexual competition and frees its members to work together in cooperation. It is at this juncture that human societies — even human civilizations — are born.”

Tucker is not himself an academic, but he is a smart journalist, and Marriage and Civilization: How Monogamy Made Us Human is the result of some 20 years of reading through the scholarly literature on marriage and thinking through the implications. It’s written for “the average reader,” and covers some “subjects that many scholars and academics in the field seem to find uncomfortable.” Indeed, Tucker comes to some rather politically incorrect views. His work is a clear-headed presentation of a “biological, anthropological, and historic understanding of the role that monogamy has played in the evolution of human society” — and by monogamy Tucker doesn’t simply mean any old union of two people, but an exclusive and more or less permanent union of a man and woman, husband and wife, father and mother.

Monogamy so understood doesn’t happen by chance. In a certain sense, “human monogamy — the pair-bonding of couples within the framework of a larger social group — is not entirely a natural institution.” After all, “monogamy does not sustain itself ‘naturally.’” And yet, when monogamy is lived out, human civilization flourishes. As Tucker puts it, “The rule is: those who form traditional families succeed; those who don’t fail.”

Because monogamy doesn’t grow on trees, “it requires rules — rules that must be continuously enforced by the members practicing it.” So, while “monogamy is manifestly a more equitable and successful way to organize a society, it is always under siege and forever fragile.” And if a society “becomes lax or indifferent about upholding its norms, the advantages will quickly unravel — as we are plainly witnessing in the America of today.”

Yet this isn’t what we witnessed in the America of mid-century. Men and women paired off, raised children as a unit, and more or less stuck together for life. To give just one statistic: Throughout the 1940s, ’50s, and early ’60s, percentages of births to unwed mothers were in the single digits. As Tucker notes, “the phenomenon of ‘single motherhood’ was virtually unknown.” In 1965, when the Moynihan Report was issued, the concern was that the out-of-wedlock birth rate for blacks was 25 percent. Today 40 percent of all children, 50 percent of Hispanics, and 70 percent of African Americans are born outside of marriage.

And this breakdown of marriage most hurts the least well-off. A leading indicator of whether someone will know poverty or prosperity is whether, growing up, he or she knew the love and security of having a married mother and father. Marriage reduces the probability of child poverty by 80 percent. The reason is simple: Marriage attaches a child’s father to his mother, and then attaches that committed pair to the child. As Tucker notes: “Children without fathers are more at risk for drug and alcohol abuse, dropping out of school, depression, delinquent behavior, crime, early sexual activity, and having illegitimate children in the next generation. They are more at risk for abuse, molestation, and incest.”

“The art of fatherhood,” however, “does not come naturally but is a skill that must be passed on from generation to generation.” Citing the work of Charles Murray, Tucker points out that the upper class is still enforcing and living by the rules of social monogamy, while the lower and middle classes are taught “the message that marriage doesn’t matter, that illegitimacy is no big deal, and that there is nothing wrong with being on the public dole.”

Yet the bulk of Tucker’s book is concerned not with these contemporary issues, but with the deep biological roots of monogamy. Unfortunately his presentation of the literature isn’t as clear as it could be, as he tells a historical story of the academic study of these origins without clearly presenting which theories stand the test of time and which were passing fads that we must reject. Still, he tells an interesting story of how “polymorphous polygamy” in chimpanzee communities — a form of “sexual communism” where “every male gets to mate with every female” — transformed into human monogamy. Tucker discusses theories that argue that, without monogamy, “the evolution of the human brain would not have been possible,” and that various biological factors affecting fitness for survival of the group as a whole led to pair-bonding. Evolution, Tucker writes, isn’t so much a matter of “Kill or Be Killed” as of “Be Fruitful and Multiply.”

The idea is that high-status males are the big winners of polygamy, but an alpha male who mates exclusively with an alpha female gets assurance that she’ll bear his — and only his — offspring, and she gets assurance that he’ll stick around for the long haul to help raise the child and protect her from aggressors. The same is then true for the beta male and beta female, and gamma, “and so on down the line — much the way it happens in high school.” Monogamy is a form of what game theorists call “Nash equilibrium”: It does not maximize the outcome for each and every individual, but it does “optimize everyone’s individual outcome in a way that maintains the integrity of the entire society.” And, more specifically, “monogamy usually emerges only where the demands of the environment require special care and protection for the young.”


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