Evolution, development, and the emergence of disgust.

Evolutionary developmental psychology typically utilizes an evolutionary lens to explain various phenomena that occur throughout development. In this paper, I argue that the converse is also important: Developmental evidence can inform evolutionary theory. In particular, knowledge about the developmental origins of a psychological trait can be used to evaluate theoretical claims about its evolved function. I use the emotion of disgust as a case study to illustrate this approach. Disgust is commonly thought to be a behavioral adaptation for avoiding the ingestion of pathogens. Given this claim, disgust should be expected to develop at a time when humans are especially vulnerable to the dangers of ingesting pathogens, during the immediate post-weaning period from about 3 to 5 years of age. Despite a strong selective pressure at this point in development, research has suggested that the emotion of disgust and the recognition of the "disgust face" do not reliably emerge until later in ontogeny, at 5 years of age or after. Given the late developmental appearance of disgust, I re-evaluate claims about its adaptive role.