It started with a kiss -- two world wars blamed on sex
The male sex drive is to blame for most of the world's conflicts, from football hooliganism to religious disputes, and even world wars, according to scientists.
The 'male warrior' instinct means that men are programmed to be aggressive towards anyone they view as an outsider, a study says.
In evolutionary terms, an instinct for violence against others helped early men improve their status, but in modern terms this can translate into large-scale wars.
In contrast, women are naturally equipped with a "tend and befriend" attitude, researchers said.
The study, published in a journal, 'Philosophical Transactions of the Royal Society B', is a review of the evolutionary evidence for the so-called "male warrior hypothesis".
It claims that in every culture throughout history, men have been more likely than women to use violence when confronted by people they consider to be outsiders.
The "tribal" attitude of men is similar to the territorial behaviour of chimpanzees, it was claimed. The study also examined evidence that suggests men have a stronger group identity than women, and that they will develop closer ties with others if they are in competition with rivals.
Although men's hostile responses most likely evolved to combat the threat from outsiders, they "might not be functional in modern times and are often counterproductive," experts said.
Over time, this has resulted in full-scale wars. Prof Mark van Vugt, who led the study, said: "A solution to conflict, which is an all too common problem in societies today, remains elusive.
"One reason for this might be the difficulty we have in changing our mindset, which has evolved over thousands of years.
"Our review of the academic literature suggests that the human mind is shaped in a way that tends to perpetuate conflict with 'outsiders'." (© Daily Telegraph, London)