No yams, no Pill

Dioscorea mexicana (Mexican yam).
photo by Nhu Nguyen

Mexican yams were the original source of the chemicals that were used in the first oral contraceptives (affectionately known as The Pill) in the mid-20th century. These inedible wild yams (not to be confused with sweet potatoes, which belong to a different family of plants, but are are sometimes mistakenly referred to as "yams")  contain a chemical called diosgenin, a type of phytoestrogen. Scientists at the Mexican pharmaceutical company Syntex extracted Diosgenin from these yams and used it to make progesterone which in turn was used in the early versions of The Pill. In nature, Mexican yams are found in the rain forests of southern Mexico and Central American and are cultivated today primarily for the interesting "turtle shell" look of the tuber root.