Wolfinger says that researchers have some ideas about why divorce would be heritable. One theory is that many children of divorce don’t learn important lessons about commitment. “All couples fight,” Wolfinger explains. “If your parents stay together, they fight and then you realize these things aren’t fatal to a marriage. If you’re from a divorced family, you don’t learn that message, and [after fights] it seems like things are untenable. And so you bounce.”
One other (albeit minor) factor is genetics. By way of explanation, Wolfinger talked through a hypothetical generation-spanning chain of assholery: “Some people are jerks, and there is some component of being a jerk that appears to be purely genetic. So: You’re a jerk, you get married, you have a kid, you don’t stay married—because you’re a dick—your kid inherits some of the genetic propensity to be a jerk. And so they get divorced.”
Though most studies have focused on divorce, some research has suggested that unmarried co-parents are more likely to break up if their parents also did. After a failed marriage or cohabitating relationship, fathers are likely to be less present in their kids’ lives than mothers are—according to census data, legal custody is granted to women in 83 percent of cases.