Human nature is trusting, open, generous, curious, compassionate, and kind. Study Bonobo Chimpanzees for reference.
By contrast, most of
human culture is myth-rooted, unscientific, deceptive, ignorant, fearful, hateful, and self-and-other-destructive. Why is that? Culture is ancient, it's been around for tens of thousands of years - most of that time dominated by violence - while
modern reason is a relative infant at only around 400 years old.
From what did that violence (Beliathon) originate (if not from [h]uman nature [Beliathon])?
These parameters link the violence to natural selection: killing competitors improves a male chimp's access to resources like food and territory - and crucially, it will happen more frequently when there is greater competition from neighbouring groups, and when the males can patrol in large numbers, with less risk to their own survival.

Chimpanzees and bonobos are our closest living evolutionary relatives
"It's a natural behaviour - it's not something that we've induced by disturbance or intervention," explained Dr Susanne Shultz, an evolutionary biologist at the University of Manchester.
Where there is heterarchy, there is reason. Where there is hierarchy, there is treason.