The Evolutionary Dominance of Ethnocentric Cooperation (2013)

"From a random start, ethnocentric strategies dominate other possible strategies (selfish, traitorous, and humanitarian) based on cooperation or non-cooperation with in-group and out-group agents. Here we show that ethnocentrism eventually overcomes its closest competitor, humanitarianism, by exploiting humanitarian cooperation across group boundaries as world population saturates."

"Selfish and traitorous strategies are self-limiting because such agents do not cooperate with agents sharing the same genes. Traitorous strategies fare even worse than selfish ones because traitors are exploited by ethnocentrics across group boundaries in the same manner as humanitarians are, via unreciprocated cooperation."

The published paper is paywalled but the preprint is accessible here: https://escholarship.org/content/qt72z42376/qt72z42376_noSplash_4b566ab45881562861ca6d054eef8e9f.pdf