In my opinion,it is more about culture than it is genetics, although I do think genetics are modified by culture in the long term.

Possibly, but look at modern times. It takes years to build social constructs that might guide us towards cooperation and non-violence. Yet, those can be overturned in an instant by a slick turn of phrase that appeals to our base instincts/caveman brain, which i believe we all have.

> I do think genetics are modified by culture in the long term.

For example, "self-domestication" by executing or ostracizing individuals that don’t fit into the culture.

They are only modified if there is some form of selection though, like for example some people say of the Dutch and their height.

In modern times it is more likely that culture and education augments genetics such that your violent tendencies are repressed, you are brought up leading a soft and comfortable life, taught to be polite and kind, etc. Contrast to maybe someone brought up in a warzone or some other place.

I mean post apocalyptic shows like the walking dead express this quite well (at least the first few seasons) where once society falls it's just a free for all and back to our roots again.