Dear Cecil: According to the History Channel's The History of Sex, the ancient Romans ate a specific plant for birth control purposes. It was described as being enormously effective, to the extent that it was extinct by the fall of the empire. I'm sure a quick Web search would tell me the story of a worthless little herb, but I'd like to hear you weigh in on this long-lost miracle drug. Brett, Memphis

Cecil replies:

We need to clarify the logic here, Brett. The fact that the Romans ate a certain plant into extinction doesn’t tell us much. Today tigers and rhinoceroses are hunted to the brink of oblivion because the tiger’s penis and rhino’s horn are thought to restore flagging virility. The fact that a lot of mopes desperately want to believe something doesn’t mean it works.

About that herb. Long before hippies thought hemp could solve all the world’s problems, Romans used an alleged wonder plant of the carrot and parsley family called silphium. It was a sort of giant fennel that grew wild near Cyrene, an ancient coastal city in North Africa. Silphium had many uses — perfume from its flowers, food from its stalk, and medicine from its juice (or resin) and roots. The Romans didn’t discover the plant’s properties — there’s evidence the Greeks and Egyptians used it as a contraceptive as early as the seventh century BC on the advice of physicians, who recommended a monthly dose that mixed a lump of resin the size of a chickpea with water. The Roman scholar Pliny the Elder described use of the resin (called laser or laserpicium) “with soft wool as a pessary to promote the menstrual discharge.” Menstrual discharge, of course, means no pregnancy. One physician in the second century AD named Soranus claimed a special recipe using silphium had been used to terminate pregnancies. In Contraception and Abortion from the Ancient World to the Renaissance (1992), medical historian John Riddle claims that modern studies show the recipe and others like it would work.

Did they? The possibility can’t be ruled out. A long list of herbs must be avoided during pregnancy because they’re abortifacients, causing contractions or damage to the lining of the uterus. If taken as ancient writers claimed, silphium might have worked as a monthly morning-after pill. Other items touted as contraceptives in antiquity include wild carrot (a silphium relative also known as Queen Anne’s lace), pennyroyal, and pomegranate. In small doses many of these are known to stimulate menstrual flow, just as silphium is supposed to have done. But some, pennyroyal for one, are poisonous — and if the abortion fails to occur, the infant can suffer birth defects.

Demographic studies suggest that the Roman world should have had a population explosion due to a low disease rate, plentiful food, and relatively few civilian war deaths. Some have seized on the fact that it didn’t as evidence that people of the era had access to effective birth control. Although silphium is no longer around, modern studies of the closely related plant asafetida show a 50 percent success rate in preventing implantation of fertilized eggs in rats, and it’s nearly 100 percent effective when fed to them within three days of mating. Likewise, studies of wild carrot have shown that it blocks production of progesterone, necessary for the uterus lining to maintain the fetus. The seeds of Queen Anne’s lace are still used as a birth control method today. Plausible as all this sounds, one can’t help raising a few objections, the most obvious being that positing a successful, society-wide planned-parenthood program that endured for centuries on the basis of a few rat experiments is a mighty long leap.

Whether it was effective or not, silphium certainly was a popular plant. Almost impossible to cultivate, it became the main source of economic power for Cyrene, a Greek colony in what’s now Libya, where it grew wild. Given the difficulty of growing it, the size of the contraceptive dose, and the number of people using the plant for other reasons, it was clear even to the ancients that it was headed for extinction, and the Cyreneans laid down strict rules regarding the silphium harvest.

Nonetheless, by the end of the first century AD silphium was no more. (The last piece reputedly was eaten by the emperor Nero, evidently unclear on the concept of menstrual flow.) After silphium disappeared, asafetida was used as a replacement, imported from what are now Iran, Iraq, and Syria. Already used by the poor because it was cheaper and more plentiful than silphium, asafetida was considered inferior from both a culinary and medicinal standpoint. Silphium may not have vanished from the face of the earth, though; some believe it was the plant now known as Ferula tingitana, a giant fennel that has returned to North Africa. Experiment if you like on your next trip to Libya; personally, I’d stick with the pill.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.