This is also a bit simplistic I think. I don't think most abortions are because of a physical defect or deformity, or at least, many abortions are not. As well, in many cultures that selected mates for their children, it usually did not exactly involve phenotype checking, but usually other kinds of economic and cultural reasons. Also, the fact that "bad" genes still exist does not mean they confer some benefit, that's a very panglossian view.