[throwaway676712]

A necessary condition for the emergence of civilization (in its broadest sense, as in the collectively organized reshaping of one's living environment for one's purposes) is a basic level of trust and cooperation.

Humans are not naturally prone to bouts of violence like other species and human societies do not tolerate impulsive violence in adults. Instead, the vast majority of human-on-human violence is deliberate: people plan, carefully and rationally, the killing of their fellow human beings in order to achieve their goals. This is known as 'war'. This is very rare among species, and more violent species cannot form complex societies at scale, despite being also quite smart in some cases (chimps, octopuses).

We even unconsciously internalized this idea to some degree, since most people are comfortable with the idea of militaries existing and being necessary but also agree that solitary murderous psychopaths should be put in prison.

[pigpop]

>Humans are not naturally prone to bouts of violence like other species

That... does not check out. There are plenty of violent people, I've met many.

[throwaway676712]

The key part is like other species and human societies do not tolerate impulsive violence in adults. All societies have rules, customs and/or arbitrage methods to regulate violence and the vast majority of people definitionally abide by them (otherwise there wouldn't be much of a society to begin with). And the vast majority of violence dealt among humans is not impulsive but deliberate (war, feuds, etc.). This is not incompatible with many people having a capacity for violence, only it's usually channeled through these deliberate methods and the extra impulsive outbursts tend to be punished.