While absent from empirical sociology, functionalist themes remained detectable in sociological theory, most notably in the works of Luhmann and Giddens. There are, however, signs of an incipient revival, as functionalist claims have recently been bolstered by developments in multilevel selection theory and in empirical research on how groups solve social dilemmas. Recent developments in evolutionary theory—especially by biologist David Sloan Wilson and anthropologists Robert Boyd and Peter Richerson—have provided strong support for structural functionalism in the form of multilevel selection theory. In this theory, culture and social structure are seen as a Darwinian (biological or cultural) adaptation at the group level.