African Clawed Frogs and the Nature of Pregnancy, 1939–60

Beginning in the late 1930s, scientists in South Africa began shipping clawed frogs (Xenopus laevis) to women’s clinics and obstetricians’ offices in Great Britain and the United States. These frogs quickly replaced rabbits as an animal source for determining the presence of human chorionic gonadotropin (hcG) in women’s urine – in other words, their bodies worked as early pregnancy tests, the most sophisticated ones available until the development of an immunoassay in the early 1960s. This paper examines clawed frogs’ movements from southern Africa to North America and Europe, from laboratory to doctors’ offices, and from scientific literature to popular culture, tracing how the technology and culture of mid-20th-century pregnancy both forged and obscured new connections between human and animal bodies. Clawed frogs’ bodies, or more particularly their ovaries’ responses to hcG, quickly became part of the process of determining women’s fertility. While Xenopus laevis went on to a surprising career as a widely used lab animal and, probably, a source of a fungus which has devastated amphibian populations in North and South America, in this paper I concentrate on how these frogs changed both medical and lay understandings of and arguments about what was natural in and about pregnancy. Clawed frogs’ journeys offer a window into two key environmental histories of the twentieth century: the global circulation of animals as medical and scientific commodities, and the technical production of natural, embodied knowledge.