This is exactly what one would predict would happen when "natural selection" gets shut off. It's basically summed up in the introduction to Idiocracy.

Other forms of selection take over, however. The selfish and underhanded, the clever who know how to keep their heads down and game the system, the real rotters, the workshy, start doing well. So you can expect a social animal's society to fall apart, and a dieback to happen. The healthy in both body and mind get preyed on by them, and burdened by the needy losers. If any population(s) survive an extinction event, they may have to start over again (depending on the level of tech they're left with - if nothing, you're back to simple natural and sexual types of selection.)