Patterns of divorce have remained surprisingly constant in almost every culture, suggesting that there may be a biological explanation for why people divorce.
Helen Fisher, an associate anthropologist at the American Museum of Natural History, said patterns she identified may have existed throughout much of human history, had acceptance of divorce been as high as it is today.
"Given the number of variations and cultural differences, it is amazing that there is any pattern at all," Fisher said. Her findings were reported at a meeting of the American Anthropological Assn.
Fisher went through the archives of the United Nations' demographic yearbooks to trace patterns of divorce in 58 countries--including Samoa, Egypt, Costa Rica, New Zealand, the Soviet Union and the United States. Records dated back to 1947.
There were three striking similarities among all cultures. Overall, women tended to divorce during their reproductive years (between 25 and 29), after being married for four years and bearing a single child. These properties of divorce, Fisher said, are unrelated to the rate, which fluctuates among societies.
"When you see similarities across totally unrelated cultures, you have to assume that there are biological factors involved," Fisher said.
Designed For Divorce
She believes that the human brain may be slightly designed for divorce; that monogamy--bonding with one person for life--is a cultural and basically human phenomenon. She said that about 97% of mammals and 50% of birds are not monogamous. Instead, they mate and stay together long enough to produce offspring.
After looking at a number of species, Fisher began to make some intriguing, though arguable, connections. "It is possible that marriage evolved about 2 million years ago. About this time, humans walked erect. The changing body--the shrinking pelvis and expanding brain--made birth very difficult. Women had to bear very helpless, infantile babies." Fisher suspects that monogamy may have evolved to raise these tiny babies.
"But these bonds did not have to last for life, only long enough to get the child through infancy, which explains the four-year bonding period," Fisher said. If the couple had another infant, the process would begin again, adding more years to the marriage.
Census records revealed that most people around the world--40%--divorce with no children; 35% with one dependent child; 19% with two; 6% with three; 2% with four; and fewer than 1% with six or more dependent children.
Fisher suspects that the evolution of infatuation and attachment sprang from monogamy. These bonding behaviors, Fisher explained, have been linked to increases in certain brain chemicals.
Frank Livingston, on the other hand, can't believe that divorce is anything more than society relaxing its cultural traditions. Livingston, a physical anthropologist at the University of Michigan, said that "this is the craziest damn thing I ever heard. Divorce is a cultural matter."