It’s Valentine’s Day, and as usual, people are presenting their loved ones with heart-shaped cards, candy, and trinkets. How did the heart shape become the symbol of true love?

Nobody’s quite sure, but it might have to do with a North African plant. During the seventh century B.C., the city-state of Cyrene had a lucrative trade in a rare, now-extinct plant: silphium. Although it was mostly used for seasoning, silphium was reputed to have an off-label use as a form of birth control. The silphium was so important to Cyrene’s economy that coins were minted that depicted the plant’s seedpod, which looks like the heart shape we know today. The theory goes that the heart shape first became associated with sex, and eventually, with love.

It’s Valentine’s Day, and as usual, people are presenting their loved ones with heart-shaped cards, candy, and trinkets. How did the heart shape become the symbol of true love?

Nobody’s quite sure, but it might have to do with a North African plant. During the seventh century B.C., the city-state of Cyrene had a lucrative trade in a rare, now-extinct plant: silphium. Although it was mostly used for seasoning, silphium was reputed to have an off-label use as a form of birth control. The silphium was so important to Cyrene’s economy that coins were minted that depicted the plant’s seedpod, which looks like the heart shape we know today. The theory goes that the heart shape first became associated with sex, and eventually, with love.Some think the heart-shape is a stylized depiction of human anatomy, representing the curved shape of breasts, buttocks, or genitalia.

The Catholic Church contends that the modern heart shape did not come along until the 17thcentury, when St. Margaret Mary Alocoque had a vision of it surrounded by thorns. This symbol became known as the Sacred Heart of Jesus and was associated with love and devotion; it began popping up often in stained-glass windows and other church iconography. But while the Sacred Heart may have popularized the shape, most scholars agree that it existed much earlier than the 1600s.

The heart shape is used worldwide to represent love, emotion, and caring. It is widely accepted as the link shape to the human heart despite the anatomical differences.