Coins from Cyrene, in what is now Libya, carry the familiar emblem, representing silphium, a now-extinct plant used as a cooking spice, perfume, aphrodisiac, and… contraceptive.
The ancient city of Cyrene in present-day Libya became so rich from farming silphium that it used the plant's shape on its currency, which bore a striking resemblance to our modern-day heart symbol.
It's found in the leaves, flowers and seeds of many plants, including silphium, which was used for birth control in the Middle Ages and perhaps is the reason why the heart became associated with sex and romantic love.