Dirt, disgust and disease: a natural history of hygiene.

Hygiene has been studied from multiple perspectives, including that of history. I define hygiene as the set of behaviours that animals, including humans, use to avoid infection. I argue that it has an ancient evolutionary history, and that most animals exhibit such behaviours because they were adaptive. In humans, the avoidance of infectious threats is motivated by the emotion of disgust. Intuition about hygiene, dirt and disease can be found underlying belief about health and disease throughout history. Purification ritual, miasma, contagion, zymotic and germ theories of disease are ideas that spread through society because they are intuitively attractive, because they are supported by evidence either from direct experience or from authoritative report and because they are consistent with existing beliefs. In contrast to much historical and anthropological assertion, I argue that hygiene behaviour and disgust predate culture and so cannot fully be explained as its product. The history of ideas about disease thus is neither entirely socially constructed nor an "heroic progress" of scientists leading the ignorant into the light. As an animal behaviour the proper domain of hygiene is biology, and without this perspective attempts at explanation are incomplete. The approaches of biological anthropology have much to offer the practice of cultural history.