IN THE CENTURY since women were finally granted the right to vote, the women's liberation movement has continued to demand equality between the sexes. The recent “Time's Up” and #MeToo campaigns highlight that these issues are still far from resolved, but it was in the 1960s that the single biggest revolution for women occurred. It transformed women's lives across the globe, and was central to the revolutionary gains that women made throughout the 1960s, 1970s, and 1980s. It was, ofcourse, the development ofthe Pill.

The first Version ofthe Pill, Enovid, was licensed as a contraceptive in the United States in 1960. Itcontains artificial versions of estrogen and progesterone, hormones that occur naturally in women. It mimics the effects of pregnancy by preventing ovulation, thickening cervical mucus to create a barrier to prevent sperm from reaching the womb, and by thinning the lining of the womb, which lowers the chance of a fertilized egg implanting itself. These combined effects mean that a woman has only a 1 percent chance of becoming pregnant when using the pill as intended. This success rate drops slightly when used imperfectly, but is still more successful than other contraceptives.

The social campaign for contraception arguably started with the social activist Margaret Sanger, who had been campaigning for women's rights to contraception for a long time before the Pill was invented. In 1916, she opened the first birth control clinic in the United States, and for a number of years, she was repeatedly arrested andjailed for maintaining a “public nuisance”; but she reopened the clinic each time she was released.

The political push for better birth control operated in conjunction with medical and pharmaceutical research. Progesterone was identified as the vital hormone for preventing ovulation in the 1930s. Methods for extracting progesterone from yams were developed, but the dosage had to be extremely high to work as a contraceptive. Progestin could be derived from progesterone, and could be given as a contraceptive in much smaller doses. Various individuals sought to invent a contraceptive pill using a synthetic progestin, but it was the Mexican chemist Luis Miramontes who led the way. Using yams, he generated a semi-synthesis of the hormone progesterone, a progestin called norethindrone. In conjunction with his co-inventors at Laboratorios Syntex SA, Carl Djerassi and George Rosenkranz, he filed a patent application for the invention in Mexico in 1951.