He never took out the trash, she nagged like a schoolteacher—pretty frustrating, sure, but it’s most likely not the reason the marriage failed. According to recent studies, genetic factors that affect personality and behavior cause as many as 40 percent of divorces. Having an extroverted personality increases the likelihood of a divorce, especially in men, and neuroticism elevates the risk for both sexes. So that loud, uber-charming guy wooing his way around the bar? Attractive—yes. Good marriage material—maybe not. And neurotics…well neurotics never really blew our hair back anyway. No loss there.

QUIZ: What’s Your Relationship Style?