An honest parent will tell you that kids are born selfish, lying, abusive people. Some are worse than others, but they all must be taught to be civil.
Evolution holds that for most any species the violent males tend to survive to pass on their genes.
It gets reinforced by female mate selection - females interest is largely triggered by displays indicating an alpha male. Whether it is females attracted to the most powerful athlete, the best looking actor or the largest toughest male in the group - she's not just picking the best possible mate to join her genes with, she's perpetuating a power based genetic system and further biasing the gene pool. It is only memes that tend to ameliorate the violent tendencies filtered genetically. Darwinian force generally reinforces undermining any source of competition. If you think about it, it is natural to steal - animals do it all the time.