stupidity

I wonder if it's hereditary because I tend to run into a lot of stupid people. Not stupid in school kinds of people but the people who think jumping off roofs of a 3 or 4 story high building, to see if they can land on the ground below and not die, kind of stupid. Or the kind of people who harass you for no good reason kind of stupid. I seem to be running into a lot of these kinds of people. So is stupidity a genetic anomaly or did these people just get dropped on their heads as babies. Either way, I wish they would stay away from me and make believe they are quarantined from the rest of the world so they do not infect others.