The Biology of Attraction

Much of courtship and mating is choreographed by nature. In fact, nature designed men and women to work together.

By Helen E. Fisher, published on January 01, 1970 - last reviewed on April 08, 2008

Why do people divorce? Bitter quarrels, insensitive remarks, lack of humor, watching too much television, inability to listen, drunkenness, sexual rejection—the reasons men or women give for why they leave a marriage are as varied as their motives for having wedded in the first place.

Overt adultery heads the list. Sterility and barrenness come next. Cruelty, particularly by the husband, ranks third among worldwide reasons for divorce. I am not surprised that adultery and infertility are paramount. Darwin theorized that people marry primarily to breed.

The Four-Year Itch

Hoping to get some insight into the nature of divorce, I turned to the demographic yearbooks of the United Nations. Divorce generally occurs early in marriage—peaking in or around the fourth year after wedding—followed by a gradual decline in divorce as more years of marriage go by. The American divorce peak hovers somewhat below the common four-year peak. Purely as a guess, I would say that this may have something to do with American attitudes toward marriage itself. We tend not to marry for economic, political, or family reasons. Instead, as anthropologist Paul Bohannen once said, "Americans marry to enhance their inner, largely secret selves."

I find this remark fascinating—and correct. We marry for love and to accentuate, balance out, or mask parts of our private selves. This is why you sometimes see a reserved accountant married to a blond bombshell or a scientist married to a poet. Perhaps it is no coincidence that the American divorce peak corresponds perfectly with the normal duration of infatuation—two to three years. If partners are not satisfied with the match, they bail out soon after the infatuation wears off. So there are exceptions to the four-year itch.

Divorce Is For The Young

Another pattern to emerge from the United Nations data regards "divorce with dependent children." Among the hundreds of millions of people recorded in 45 societies between 1950 and 1989, 39 percent of all divorces occurred among couples with no dependent children, 26 percent among those with one dependent child, 19 percent among couples with two, 7 percent among those with three children, 3 percent among couples with four young, and couples with five or more dependent young rarely split. Hence, it appears that the more children a couple bear, the less likely they are to divorce.

This pattern is less conclusively demonstrated by the U.N. data than the first two. Yet it is strongly suggested and it makes genetic sense. From a Darwinian perspective, couples with no children should break up; both individuals will mate again and probably go on to bear young—ensuring their genetic futures. As couples bear more children they become less economically able to abandon their growing family. And it is genetically logical that they remain together to raise their flock.

Planned Obsolescence Of The Pair Bond

Marriage clearly shows several general patterns of decay. Divorce counts peak among couples married about four years. And the longer a couple remain together, the older the partners get, and probably the more offspring they produce, the less likely spouses are to leave each other.

This is not to say that everybody fits this mold. But Shakespeare did. Etched in Shakespeare's marriage and in all these other divorces recorded from around the world is a blue print, a primitive design. The human animal seems built to court, to fall in love, and to marry one person at a time; then, at the height of our reproductive years, often with single child, we divorce; then, a few years later, we remarry once again.

Adapted from Anatomy of Love; The Natural History of Monogamy, Adultery, and Divorce, by Helen E. Fisher. Copyright C 1992 by Helen E. Fisher. Reprinted by arrangement with W. W. Norton & Co., Inc.