Robin Ian MacDonald Dunbar (born 28 June 1947) is a British biological anthropologist, evolutionary psychologist, and specialist in primate behaviour. Dunbar is professor emeritus of evolutionary psychology of the Social and Evolutionary Neuroscience Research Group in the Department of Experimental Psychology at the University of Oxford. He is best known for formulating Dunbar's number, a measurement of the "cognitive limit to the number of individuals with whom any one person can maintain stable relationships". Source: Wikipedia (en)