ABSTRACT

In the early 1940s, Australian sheep ranchers began to notice a peculiar and frightening trend, as the ewes became sterile and fewer lambs were counted each spring. By the mid-1940s, the ranching industry in Australia was in a state of crisis and faced certain financial ruin unless the cause of the mysterious infertility in the sheep could be found. What could be causing this disastrous sterility? Genetic mutation? Radiation? Poisonous chemicals? The Australian department of agriculture was called in. A cadre of veterinary doctors and scientists identified clover as the source of the sterility. The ranchers were unaware that the innocuous-looking clover (

Trifolium subterraneum

), which they had recently begun planting in their fields to feed the sheep, had been producing large quantities of estrogen-mimicking compounds. It took another decade before scientists finally pinned down the exact compounds that were causing the sterility, namely the isoflavones genistein and formononetin.