There are (though they are changing now) psychopathic headhunter societies in places like new guinea that have lived for tens of thousands of years by murdering members of other tribes, mainly as a rite of passage, although also for cannibalism. They have outlived all other collapsed civilisations, like the mayans, aztecs, romans by keeping to themselves and keeping their population down so that they do not exhaust their resources. Although kuru, or creutzfeld-jacob disease is endemic there, schizophrenia is completely absent for reasons which are inexplicable which does tend to point to them being physically and mentally healthier than most developed countries.