Medicine may have saved the lives of many people who have been suffering from diseases, birth defects, and other such malignancies. But, by doing so, we are weakening our race as a whole.
Darwinian evolution is where the weakest die because the stronger ones are better able to survive. By introducing medicine, we are allowing the strong ones and weak ones to survive. By keeping these genetic defects in the human gene pool, we cripple ourselves.
Maybe medicine is a good thing after all. By letting the people with genetic defects survive, maybe they have another gene which will allow them to survive something no one else could. By keeping as many people as possible alive, we are increasing the genetic diversity, which will allow our race to survive larger and greater epidemics and worldwide disaster.
I do admit that genetic engineering is a good thing. By going straight to the source of the problem, we may be able to root out most birth defects and lower the infant mortality rate and help the human race as a whole.
Which also will
Increase the rate at which we over-populate the earth and cause the natural resources to run out faster, ending the long walk that we call the human race.
The question here is: Which will happen first; overpopulation, or a population cutting worldwide disaster?