From “Seven Deadly Sins: The Biology of Being Human” by Guy Leschziner
By and large, we humans are a peaceful species, often able to cohabit in large communities in a non-violent manner. Yet, simultaneously, we possess a frightening propensity for violence, murder and mayhem. This apparent contradiction has been much debated. Some argue that the human race is intrinsically pacifist, but that violence is a function of our culture, while others propose the diametrical opposite: that our violent nature is reined in by cultural restraints. However, it appears that this duality is a little more complicated.
While our ability to murder on a massive scale, to organise and work with others to inflict death and destruction, is not in question, some researchers suggest that our intrinsic predisposition to reactive violence or aggression is extremely low indeed. Observations of pre-industrialised societies have found little evidence of reactive aggression at all. For example, ethnographers have observed the Ache people of Paraguay for decades, without seeing even very minor acts of reactive violence.