Male sex drive is at the root of most conflict in the world, from football violence to wars, scientists claim.
A review of psychological evidence concludes that men are shaped by evolution to be aggressive towards "outsiders". The tendency, at the heart of all inter-tribal violence, emerged through natural selection as a result of competition for mates.
Today it can be seen in wars as well as clashes involving rival gangs, football fans or religious groups, say researchers.
Women, on the other hand, have evolved to resolve conflicts peacefully, programming them to "tend and befriend" to protect offspring.
Professor Mark van Vugt, from the Institute for Cognitive and Evolutionary Anthropology at Oxford University, said: "A solution to conflict... remains elusive. One reason for this might be the difficulty we have in changing our mindset, which has evolved over thousands of years.
"The human mind is shaped in a way that tends to perpetuate conflict with 'outsiders'."
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