Evolution of human serial pairbonding.

Data on divorce taken for all available years between 1947 and 1981 from the Demographic Yearbooks of the United Nations on 58 peoples illustrate that divorce has a consistent pattern. Divorces exhibit a skewed distribution, characterized by the occurrence of the mode early in marriage (with a divorce peak on or around the fourth year) and a gradual, long-tailed decline following this peak. Divorce risk peaks in age category 25-29 for males and age categories 20-24 and 25-29 for females, the height of reproductive and parenting years, and divorce counts peak among couples with two or fewer children. These properties of divorce are unrelated to divorce rate; they occur in societies with both high and low divorce rates. Data on available horticultural and gathering/hunting societies illustrate that divorce also peaks among young couples early in marriage. Remarriage by divorced and widowed individuals of reproductive age is also common cross-culturally. It is proposed that the above four-year modal marriage duration among couples of reproductive age who divorce reflects a hominid reproductive strategy that probably evolved some time after the appearance of Homo in response to increased female "reproductive burden" and functioned to ensure the survival of the hominid infant through weaning. Serial pairbonding during the female's reproductive years had ancestral adaptive advantages, producing the modern cross-cultural pattern of serial pairbonding.