Rethinking Transformation and Emergence: Cattle, E. coli O157:H7, and Evolutionary History

The development of “evolutionary history” provides historians with the opportunity to rethink historical change, specifically the human shaping of the evolution of nonhuman life-forms. This paper explores two examples of such “shaping”: global cattle breeding and an “emerging pathogen,” E. coli O157:H7. Most contemporary cattle are the product of deliberate regimes of selective breeding and artificial insemination designed to enhance certain “innate” bovine biological proclivities (milk yields, for example). The result is an immense global cattle population of extremely productive but rather fragile animals, and a demonstrably homogenized bovine gene pool. E-coli bacteria, meanwhile, are extremely ancient – far older than hominins – and during their long evolution they have become adapted to life in mammalian intestines. However, in 1982, a deadly new form of the bacterium was first recorded, E. coli O157:H7. Unlike its relatively benign ancestors, this pathogen is very dangerous: its defining clinical features are bloody diarrhoea and, in serious cases, hemolytic-uremic syndrome (HUS) and death. E. coli O157:H7 is often called an “emergent” disease: for humans at least, it is a new disease entity. Microbiologists have produced a evolutionary history of E. coli O157:H7, showing points when it acquired the toxins responsible for its virulence. Other scholars have explored the environmental transformations causing the possible emergence and spread of the pathogen: industrialized livestock farming, grain-feeding, antibiotics, and poor slaughterhouse hygiene. These two cases of evolutionary history are clearly rather different. The first was an intentional project of transformation, recorded in innumerable texts. The second was an unintentional case of emergence, largely devoid of textual or material traces. They are, however, intertwined, for the planned bodies of cattle produced the intestinal milieu for the unplanned emergence of O157:H7. One type of evolutionary history is nested within another: through such “nestings” we can rethink chains of historical causation.