When a person before the age of “modern medicine” say 1900 or so had a terminal illness, natural selection and the absense of a cure would cause that particular person to die prematurely, in which case, they could not pass their defect or disease on to any offspring (if they didn’t have any yet).
Now, medicine has evolved to where we are keeping people serious diseases such as depression, diabetes, asthma, etc alive with drugs. Diabetes, in particular, is a problem of the future as the rate of diagnosis is climbing every year.
This hits on a personal note because I have serious asthma and probably would have died before the age of 5 if there wasn’t today’s medicine. Now I am worried about passing that on to any children I might have, and I’m considering not having any due to this and some other conditions I have, such as degenerated discs in my back at the age of 15. I’m 28 now….
My feeling is that the reason health care costs are astronomical is because each person has more problems today because we aren’t weeding out the weak or defective.