Why are mass shootings becoming more common (since the 80s)?

[Shankapotomus]

10. If we take as a given

that males are evolutionarily prone to use violence as a problem solver, with less and less imperialist wars on foreign populations to use as an outlet for that natural aggression, that violent nature turns inward, towards ones own people.

The European male (and I am one so I have no personal stake in attacking them) has been fighting wars and imposing his will on weaker foreign populations for thousands of years. There has to be some evolutionary effect from that. That when something is in their way, they are not evolutionarily adapted to run and hide as a member of a suppressed people would do. Since the European male (in this case American male) has traditionally been the victor and conquerer (ex. The indiginous N. American population), their coping strategies involve suppression of others, not submission or evasion. When problems arise with others the cultural lesson has been not negotiate but try to impose your will.

This is all just a hypotheses but, if it makes sense, we should start to see more of this in China as it becomes a dominant world power.