Gregory Albery

In humans and wild animals, pathogens impose costs on both the individual and the social group as a whole. To minimise these costs, group-living species have evolved many hygienic and immune traits that benefit from cooperation between individuals, thereby subjecting them to the laws of social evolution. Such social contracts include reciprocal grooming, altruistic self-isolation, spiteful treatment of infected individuals, and costly immune resistance responses. In highly social animals such as eusocial insects, these traits often present as complex “collective” or “social” immune systems. Even the expression of individual-level phenotypes such as sickness behaviours and immunological tolerance can depend heavily on social context, and understanding whether such responses present a benefit for the individual, the group, or both can be critical for understanding their functions and eco-evolutionary consequences. As yet, our consideration of these traits has mostly concerned individuals, or collective immunity in eusocial insect taxa. Consequently, their broader epidemiological consequences and implications for the evolution of sociality are relatively unclear. Here, I describe a wide number of socially evolved hygienic and immune traits in wild animals, both in social insects and in other taxa. I outline the problems that emerge when evolving and enforcing these anti-disease functions, discussing the conflicts that arise and their implications for evolutionary and cultural transitions in social complexity, and their potential analogues in human public health.