Going through harmful and dysphoric group experiences can act as a mechanism to groom people for extreme self-sacrifice, such as terrorist attacks, an evolutionary biology study has found.
The human behaviour of being prepared to die for the benefit of non-relatives is an evolutionary puzzle. It is not a modern phenomenon - soldiers or warriors willing to die for their country or community are an example that stretches back as far as the history of war.
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But this form of so-called extreme altruism doesn't help to pass on an individual's genes, because direct relatives do not necessarily benefit from the behaviour any more than unrelated people. As a result, its evolutionary origin has been unclear.
An evolutionary explanation for this behaviour put forward in a study published in the journal Scientific Reports is that sharing extremely negative experiences can boost group cooperation. This was to improve the future prospects of the group, which were a more important factor than the history - or ancestry - of the group, the study found.
"While previous research in evolutionary biology has identified a number of paths for the evolution of cooperation, this study introduces a novel, previously under-appreciated but very powerful mechanism: conditioning acts of extreme cooperation on shared prior experience," said study author Sergey Gavrilets of the University of Tennessee and the National Institute for Mathematical and Biological Synthesis, in a statement.
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The study used evolutionary computer modelling techniques to test several hypotheses of how extreme self-sacrifice could arise and persist in human populations. Empirical research on behaviour of groups that go through painful rituals or hazing supported the hypothesis. It held true across groups from Vietnam War veterans, American university fraternities and sororities, Brazilian Jiu Jitsu practitioners and English Premier League football fans.
The process of hazing or other very unpleasant rituals - such as ritual belt whipping in the case of Brazilian Jiu Jitsu - led to a sense of 'identity fusion', blurring the personal with the social.
"Practically, our account of how shared dysphoric experiences produce identity fusion helps us better understand such pressing social issues as suicide terrorism, holy wars, sectarian violence, gang-related violence, and other forms of intergroup conflict," the authors write in the paper.
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