The red-beard evolutionary explanation of human sociality

Recent evolutionary studies on cooperation devote specific attention to non-verbal expressions of emotions. In this paper, I examine Robert Frank's popular attempt to explain emotions, non-verbal markers and social behaviours. Following this line of work, I focus on the green-beard explanation of social behaviours. In response to the criticisms raised against this controversial ultimate explanation, based on resources found in Frank's work, I propose an alternative red-beard explanation of human sociality. The red-beard explanation explains the emergence and evolution of emotions, a proximate cause, rather than patterns of behaviour. In contrast to simple evolutionary models that invoke a green-beard mechanism, I demonstrate that the red-beard explanation can be evolutionary stable. Social emotions are a common cause of a social behaviour and a phenotypic marker and therefore cooperative behaviour cannot be suppressed without also changing the marker.