The genetic mechanism of selfishness and altruism in parent-offspring coadaptation.

The social bond between parents and offspring is characterized by coadaptation and balance between altruistic and selfish tendencies. However, its underlying genetic mechanism remains poorly understood. Using transcriptomic screens in the subsocial European earwig, , we found the expression of more than 1600 genes associated with experimentally manipulated parenting. We identified two genes, and , each showing evidence of differential coexpression between treatments in mothers and their offspring. In vivo RNAi experiments confirmed direct and indirect genetic effects of and on behavior and fitness, including maternal food provisioning and reproduction, and offspring development and survival. The direction of the effects consistently indicated a reciprocally altruistic function for and a reciprocally selfish function for . Further metabolic pathway analyses suggested roles for restricted endogenous dopaminergic reward, mediated chemical communication and a link to insulin signaling, juvenile hormone, and vitellogenin in parent-offspring coadaptation and social evolution.