Watching, as usual, the least offensive thing I could find on the TV while I used my exercise machine, I found myself seeing The Killing Fields, about the Khmer Rouge in Cambodia. Everyone in this film was risking, and trying to avoid, torture and death at short notice, as murderously inclined collections of people washed around the country, and other people tried to guess where they would go next and what would be the best direction in which to run.
Now the effects of the Khmer Rouge were obviously terrible in one sense, and (like other instances of communist revolution) destructive towards the more middle and upper-class elements of society. However, such a condition of society would seem to select against some relatively dysfunctional genes. And it seems very reminiscent of the gang warfare now prevalent in many inner cities, as one hears.
So perhaps it is the case that, whenever relieved of immediate pressures of any other kind, such as the need to work in some way to keep alive, human beings are programmed to form up in groups to start fighting one another. Like mating rituals, this clearly serves a function in selecting against unfavourable genes, and selecting in favour of intelligence sufficient to guess accurately who is likely to want to kill one, provided it is combined with an ability to run fast. Both very low intelligence and weak legs are being selected against.
However unpleasant, this may be an inevitable feature of human society. Perhaps civilisation is intrinsically unstable, because it tends to produce forces that promote certain changes in the gene pool, these changes being of a kind perceived as dangerous because they are potentially maladaptive for survival, and this produces a hardwired backlash in favour of more primitive conditions.