Cooperation in adversity: an evolutionary approach

Abstract

Throughout the organic world cooperation provides mutual benefit but is vulnerable to exploitation from free-riders. Over the last 30 years work in evolutionary biology and game theory has provided understanding of the conditions necessary for the maintenance of cooperation, and advances in gene-culture coevolution theory have extended this understanding to our own species. After a preamble on the evolutionary analysis of behaviour I outline this work. I then consider how cooperation is influenced by environmental adversity and find that in non-human species it is enhanced under these circumstances in a range of taxa. In a sample of human cases the same result is found in a majority, but the opposite effect in some when socioeconomic position is the measure of quality. In anthropological studies of societies living in extremis, again the opposite effect is found. I propose a sigmoid shape for the relationship between adversity and fitness (or human well-being) and a consequent inverted-U shaped relationship between adversity and the benefit of cooperation. Most of the data presented on the relationship between adversity and cooperation are consistent with this proposal. I suggest further tests of the proposal and place the study of cooperation in the broader context of prosociality.