Disgust originates largely to reduce contact with foreigners, and the deviant or marginalized

Rottman, J., DeJesus, J. M., & Gerdin, E. (forthcoming). The social origins of disgust. In N. Strohminger & V. Kumar (Eds.), The moral psychology of disgust. London: Rowman & Littlefield. http://www.joshuarottman.com/publications.html

Despite being perfectly nutritious, consuming bugs is considered gross in many cultures [...] What is the function of such an irrational response, one that may continue to endanger the natural environment? Do people experience disgust toward insects because of perceived disease risks? Are people reacting to the reminder that they are eating an animal, in the same way that many people react negatively to eating a whole fish (with its head and eyes) compared to a fish fillet? We argue that social risks may instead be motivating this reaction. More broadly, moving beyond the example of entomophagy, we claim that disgust is much more deeply enmeshed in social and moral considerations than has been previously acknowledged. [...] In this chapter, we propose an alternative to the recurrent claim that disgust evolved for the sole purpose of facilitating the avoidance of toxins and infectious disease [...]

We do not deny that disease avoidance is a crucial element of disgust, but we believe that there is more to the story. We argue that a central component of the adaptive value of disgust lies in the motivation it provides for reducing contact with people who are considered to be deviant or marginalized, both for disease-related and reputation-related reasons (see Chudek and Henrich 2011, for a discussion of the adaptive function of social norms). We hereby introduce the “Social Origins” hypothesis as a crucial addition to the Physical Origins hypothesis to provide a more complete evolutionary account of disgust. According to our hypothesis, disgust originated largely as a functional response for preventing contact with foreigners or people acting in non-normative ways. This response serves a dual adaptive purpose: reducing human-borne illnesses and maintaining reputational status within one’s social group, either separately or simultaneously. Therefore, while avoiding pathogens is a crucial component of a full explanation of disgust’s origins and functions, we argue that simple disease avoidance was not the sole or even the primary driver of the evolution of disgust in humans.