Would the world be better if people below a certain IQ threshold were not allowed to reproduce? The facile answer is "Yes!" Considered more carefully, I believe not.
Genes are multipotent and intelligence - emotional and cognitive - is a multigene expression. Add variable penetrance, synergists and antagonists and proteonomic modulators and everything becomes exceedingly complex. Losing stupid people could mean losing much more than we are aware of.
Stupidity is a single expressed local minimum. It is not an absolute determined trajectory.
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