Unlike our closest primate relatives, chimpanzees and bonobos, humans form strong intergroup ties which can mitigate coalitionary aggression and make peace possible. However, such bonds can also be used to build larger alliances that take such conflicts to a new level of magnitude, supported by cultural and linguistic proficiencies. Arizona State University and University of Utah professor Polly Wiessner addresses intergroup ties between humans, chimpanzees and bonobos, explores some of the possible evolutionary developments that contributed to the human disposition to form mutually supportive external bonds, and then discusses the impact of social ties on coalitionary action. (#37383)