Steven Hawking (ALS). Beethoven (deaf), Van Gogh (mentally ill), John Nash (Nobel laureate mathemation, schizophrenic), Helen Keller (blind and deaf).
There is no reason to believe Beethoven’s deafness had any genetic basis.
It is not known what Van Gogh’s mental illness was caused by, but odds are it was not genetic.
Nobody has a clue at this point in time what causes schizophrenia, but a simple genetic cause is unlikely.
Helen Keller was born perfectly normal and lost her sight and hearing as the result of disease when a toddler.
Most birth defects are not caused by simple genetic defects but by complex interactions between genes and intrauterine development events. Or simply by the intrauterine events alone.
My point is that claims that we will be able to weed out “defective” people are wildly overblown. Most defects are not caused directly by genetic problems.
Downs’ Syndrome is not a good example of where we’re headed. It is one of the few problems that is both common and easy to test for.
Four out of five ain’t bad.