That Darwin’s contributions toward understanding the evolution of social behavior were significant is undeniable. In the Origin of Species there was detailed treatment of “social evolution,” and this thinking led to much discussion, something given fresh impetus and further fuel in the Descent of Man. Darwin’s chapters in Descent on “The Comparison of the Mental Powers of Man and the Lower Animals” and “On the Development of the Intellectual and Moral Faculties during Primeval and Civilised Times” led to a great deal of speculation and comment with regard to the possibility of social and perhaps moral instincts in lower animals. Yet, as we shall see, although Darwin explicitly engaged this issue, its significance in evolutionary thinking, especially regarding the evolution of behavior, waxed and waned.

Social Insects and Social Instincts

Passages from both the Origin and Descent illuminate Darwin’s position with regard to selection acting on traits involved in social behavior. The following oft-quoted passage, from chapter 3, “The Struggle for Existence,” illustrates the breadth of action that Darwin (1859, 62) assigns to the struggle leading straight into the mechanism of natural selection: “I should premise that I use the term struggle for existence in a large and metaphorical sense, including dependence of one being on another and including (which is more important) not only the life of the individual, but success in leaving progeny.” The problem is that (seemingly) success is at the individual level and the group gets overlooked and lost. This is no recipe for social behavior. Darwin’s solution, however, involved the idea that selection could act at a level above the individual: a family, a colony, a social group, or a community. Later in the Origin, where Darwin is dealing mostly with the social insects, we see how this insight comes into play. Darwin recognizes the difficulty that the neuter insects with their distinct morphology and habits present to his theory and thus, in typical Darwinian style, he does his best to explain and diffuse this potentially devastating case.