Love may well be one of the most studied, but least understood, behaviours. More than 20 years ago, the biological anthropologist Helen Fisher studied 166 societies and found evidence of romantic love—the kind that leaves one breathless and euphoric—in 147 of them. This ubiquity, said Schwartz, an HMS associate professor of psychiatry at McLean Hospital in Belmont, Mass., indicates that “there’s good reason to suspect that romantic love is kept alive by something basic to our biological nature.”
