Norms about hygiene and violence have both shown a tendency to become increasingly
strict, in the sense that the handling of bodily fluids and the use of violence have become
increasingly restricted. The generality of this directional change across a large number of
societies has not been captured by previous explanations. We propose an explanation of
the directional change that is based on the aggregation of everyday interactions. This theory
posits that directional norm change can come about if there is an asymmetry in punishment …

Norms about hygiene and violence have both shown a tendency to become increasingly
strict, in the sense that the handling of bodily fluids and the use of violence have become
increasingly restricted. The generality of this directional change across a large number of
societies has not been captured by previous explanations. We propose an explanation of
the directional change that is based on the aggregation of everyday interactions. This theory
posits that directional norm change can come about if there is an asymmetry in punishment …