evolution

Parasitism evolved at least 223 times, far more than the previous estimate of 60. It arose more times in certain phyla (e.g., arthropods, nematodes, flatworms, and mollusks) than in others. Today, about half of all animal species are parasitic.
As a society, we never grew up beyond high school. Not being smart continues to be cool. Rejecting the collective wisdom of scientists, economists, academics, and journalists is applauded. Spurning the "establishment" has become the new national pastime.