Michael Ruse reminisces about Ernst Mayer (1904-2005) and his work. For the social scientist this obituary in Philosphy and Biology about one of the great 20th century biologists is stimulating because it shows how the contested the idea of selection as the driver of biological evolution was in different periods of the discipline. One of the great questions in social evolution is precisely how much selection plays a role in the transformation of social and cultural systems.