Itch

Divorce occurred most frequently among couples at the height of their reproductive and parenting years—for men, ages 25 to 29, and for women, ages 20 to 24 and 25 to 29—and among those with one dependent child.

In more contemporary hunter-gatherer societies, women tend to bear their children about four years apart. After a child is weaned at around age four, the child often joins a playgroup and is cared for by older siblings. This allows unhappy couples to break up and find a more suitable partner.

Serial pair bonding may have been beneficial to survival among our forebears because having children with more than one partner produces offspring with greater genetic variety and a wider range of skills. Hence, in the changeable environment of ancient Africa, some offspring would have had a better chance of enduring.

The four-year divorce peak among modern humans may represent the remains of an ancestral reproductive strategy to stay bonded long enough to raise a child.

By understanding this susceptibility, we might anticipate, and perhaps be able to avoid, the four-year itch.