Welcome to the first installment of our series chronicling the history of the birth control pill, from our discovery of how hormones work, to the synthesis of these hormones from an inedible wild Mexican yam, to the creation of a pill that changed the world.

Underneath the surface of a large swath of Southern Mexico’s jungles lay the enormous roots of a wild yam, Dioscorea composita, known locally as barbasco. Mostly it was considered a nuisance, as it could get in the way of subsistence agriculture, but it did have its uses. Indigenous people used it as a fish poison, and traditional Mesoamerican healers used it to treat rheumatism, snakebites, muscular pain, and skin conditions. When the root was fermented in alcohol and put on aching joints, it was believed to work as a pain reliever.

The idea of a birth control pill was born in 1912 when Margaret Sanger dreamed of a “magic pill.”

Barbasco’s medicinal uses might not be surprising, given that scientists derived a chemical from the yam that led to the development of cortisone and oral contraceptives, both of which had sizable impacts on medicine and society. Oral contraceptives would not have been possible without a cheap and abundant source of progesterone, which was easily synthesized from the root after an American chemist, Russell Marker, discovered a process for converting a cholesterol found in barbasco’s roots to progesterone, a key ingredient in the Pill.

In the decades before this chemist’s excursion to Mexico, first-wave feminism was brewing in turn-of-the-century United States, and birth-control pioneer Margaret Sanger demanded access to contraception — in 1915, she invented the term “birth control,” and as early as 1912, the idea of a birth control pill had been envisioned — again, by Sanger, who wrote of her hope for a “magic pill.” A nurse, Sanger was spurred to action by the horror of watching women die prematurely after having too many children, while other women died from botched abortions.

Coinciding with feminist agitation, scientists were piecing together the complex system of the body’s “chemical messengers,” hormones. Between 1890 and 1905, they learned that ovaries secrete hormones that are transported through the bloodstream and which have physiological effects. By the end of the 1920s, it was known that ovaries secrete different chemicals depending on whether or not there is a pregnancy; and after ovulation the hormone progesterone is secreted, during which time no new eggs are released by the ovary.

After determining the function of hormones, scientists sought to isolate them. Initially they contracted with slaughterhouses and extracted them from the glands of animals. By the ’30s the hormone industry was based in Europe, and sex hormones were generally derived from cholesterol from cattle’s spinal cords. Sex hormones could also be derived from the urine of humans, but this method resulted in very small quantities.

There was much to discover about hormones’ functions, and scientists had some interesting hypotheses and conducted equally interesting experiments. For example, in 1937, scientists at the University of Pennsylvania postulated that a body could be “tricked” into thinking it was pregnant. They injected rabbits with progesterone and found that their ovaries didn’t release eggs when expected to do so — the progesterone sent a signal to the rabbit’s brain that it was already pregnant, which suppressed ovulation.

However, during the ’30s and ’40s, when scientists were kicking such ideas around, there was no known method of extracting enough progesterone from animals to provide the therapy to the people who needed it — 80,000 pigs’ ovaries were needed to extract a minuscule amount of estrogen — and cost would have been prohibitive to virtually anyone who wanted such a drug. Science needed to find a cost-effective method of producing large quantities of hormones, such as progesterone.

In the next installment of this series, we’ll meet Russell Marker, the iconoclastic chemist who finagled large quantities of progesterone from a wild yam he found in the jungles of Mexico.