If people were only fighting and competing throughout human evolution, natural selection would lead to more lefties being the ones that made it until there were so many of them, that it was no longer a rare asset.
Se as pessoas apenas lutassem e competissem durante a evolução humana a seleção natural faria com que  os canhotos tivessem mais vantagem até que o seu número fosse tão grande que deixariam de ser um trunfo raro.