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In the last 200 years or so, healthcare and therapy has been revolutionized. Mortality rates are going down everywhere. Even if the disease is terminal, medicine can prolong life for quite a while. Does this not affect natural selection's mechanisms as the genes for these disorders(assuming they are heritable of course) still remain in the gene pool? I'm not questioning the morals of whether sick people should be saved or not. I'm just wondering has there been any study/simulation of medicine's effect on evolution and natural selection.