Scitech | How heroes evolved

Science explores the beginnings of courage and combativeness

It’s practically a Canadian personality trait. Right up there alongside our lofty ideals of niceness, modesty, and tolerance rests a belief that war is fundamentally irrational. The costs – both human lives and material factors – exceed the benefits by far. Or so we thought. Hold on tight you granola-crunching Canucks, the pillars of our morality are about to be shaken.

According to a paper recently published in the Proceedings of the Royal Society, Biological Sciences, war may have once been a good thing. Marc Feldman, a professor, and Laurent Lehmann, a post doctoral fellow at Stanford University, discovered that wars among groups of early humans may have been rational according to evolutionary standards because the benefits for the group outweighed the costs to the individual.

Using a population-genetics model, Lehmann and Feldman suggested that reproduction-enhancing plunder obtained through conquest may have played a role in the evolution of aggressive behaviour among men. In their model, resources include additional women for males to mate with and additional territory for females. Because both additional mates and territory increase the number of children a group can support, traits that make groups more successful in war are favoured – even if, as in the case of belligerence and bravery, the traits are costly.

Through their model, Lehmann and Feldman found that belligerence was beneficial because it makes a group more likely to start a war – despite its high costs in time and energy. Bravery, too, was beneficial, because the benefits of victory that came with courage outweighed the increased risk of death.

The study results suggest that these two traits may have evolved because men mated with women from conquered tribes. Women from the winning groups benefited as well, by getting resources, like food and shelter, to support children.

According to Lehmann, the findings have received a lot of media attention, but have not exactly rocked the science community.

“The question and the model are quite standard. The predictions that come out are also standard…. It’s the behaviours examined that catch the imagination,” he said.

Indeed, it’s tempting to project the model on today’s seemingly aggressive society, but Lehmann warned that their model is based on how humans used to live – in small, isolated groups. Prehistoric conditions don’t translate well into today’s state-versus-state warfare.

“The thing that is really important is that you need kinship ties. You need that group of homogeneous individuals whether it is genetically transmitted or culturally transmitted,” Lehmann said.

As size of groups and mating between groups increases, kinship – relatedness within a group – will decrease. And as kinship decreases, belligerence and bravery lose their value, because part of the value of bravery is that even if you die, your siblings will still be around to pass on the genes that you share with them. The model shows that if belligerence and bravery are passed on by genes alone, the maximum group size in which the traits may have evolved is roughly 50 people.

To explore the possibility of larger groups, Lehmann and Feldman considered cultural transmission of belligerence and bravery. Culturally transmitted aggression occurs when aggression is learnt, rather than passed genetically, and can evolve no matter the group size.

Yet Lehmann remained unconvinced of the applicability of his results on modern-day warfare.

“Decisions taken by states today are more complicated. There are economic models which attempt to explain why states go to war, but our model doesn’t apply to this situation,” Lehmann said.

Still, this is the moment when Canadians can breathe a sigh of relief. If wanting to go to war was ever a cultural phenomenon of our distant past, we most certainly would have left it to our less rational cousins down South.


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