Here’s a fun fact: the universal symbol of love and affection has its origins in an herb that let the ancients fornicate [like rabbits] free from the worries of pregnancy. Yep, thats right, the heart shaped sign that we all know and love originated as the universal sign for a natural birth control pill.

The prized plant became such a key pillar of the Cyrenean economy that its likeness was stamped upon many of the city’s gold and silver coins. The images often depicted a regal-looking woman sitting in a chair, with one hand touching the herb and her other hand pointing at her genitals. The plant was known as silphium or laserwort, and its heart-shaped fruit brought the ancient world a highly sought-after freedom: the opportunity to enjoy sex with very little risk of pregnancy.

As word of the birth-control wonder-herb spread through ancient Europe, Africa, and Asia, a market for the versatile fennel developed rapidly. The seeds became widely used among the world’s wealthier nations, including the citizens of ancient Greece, Rome, Egypt, and India. By some accounts the silphium seed was also a potent aphrodisiac, a property which considerably compounded its perceived value. The Roman bard Catullus famously alluded to its sexual properties in one of his love poems, where he declared that he and his lover would share as many kisses as there were grains of sand on Cyrene’s silphium shores. More plainly, “We can make love so long as we have silphium.”

For centuries the north African city thrived on its laserwort bounty. The seeds of the fickle fennel came into such high demand that they were eventually worth their weight in silver. The Roman government went so far as to store a cache of the herb in the official treasury. Most of the primitive silver and gold coins from Cyrene were stamped with images of the silphium, some depicting just a single heart-shaped seed. It is thought by many historians that this ancient icon of unfettered lovemaking is the origin of today’s ubiquitous “I love you” heart symbol.

Unlike many other medicines of its time, silphium was not thought of as a mere folk remedy; Scholars and doctors of the day openly praised the plant’s effectiveness as a contraceptive. Ancient Rome’s foremost gynecologist–a physician named Soranus–wrote that women should drink the silphium juice with water once a month since “it not only prevents conception but also destroys anything existing.” Alternatively, a tuft of wool could be soaked in the juice and inserted into the vagina as a pessary. The herb’s effectiveness and widespread use is evidenced by the observation that Rome’s birth rate decreased during laserwort’s heyday, despite increasing life expectancy, plentiful food, and relatively few wars or epidemics.

Unfortunately, modern science will probably never determine whether the fennel’s extract was an effective form of parenthood prevention, nor will it measure laserwort’s merit as a medicine. By the end of the first century AD, following a fifty year decline in silphium numbers, the Roman historian Pliny the Elder recorded the plant’s lamentable extinction. The last remaining stalk of the laserwort was snipped and sent to Emperor Nero as a “curiosity,” and thus ended six hundred years of reliable birth control.