A biological anthropologist at Rutgers who spent the last several years studying marriage and divorce data suggests that the so-called “7-year itch” — the psychological term referring to an observed decline in happiness after 7 years of marriage — is off by 3 years.
In a fascinating email to Scientific American, Helen Fisher explains that what might be better called the “4-year itch” has to do with how most mammals are only monogamous through their offspring’s toddlerhood. This pattern was replicated in some hunter-gather societies, where kids were raised by their parents until they hit 4, after which “the village” took over. Then, the parents were free to mate with others if they chose to.
Fisher, the author of Anatomy of Love: The Natural History of Monogamy, Adultery and Divorce, doesn’t get into what you might actually do with this research. But remember that, when the wife suddenly expresses an urge to move out and keep the dog 4 years into your marriage, she doesn’t mean anything by it — it’s just science.