i just wanted to through tis excerpt in just because it has always spoken to me, and it fits the topic here. it is from aldous huxley (author of 'brave new world' - 1932) from a collection of essays of his called 'brave new world revisited' - 1958.
" In this second half of the twentieth century we do nothing systematic about our breeding; but in our random and unregulated way we are not only over-populating our planet, we are also, it would seem, making sure that these greater numbers shall be of biologically poorer quality. In the bad old days children with considerable, or even with slight, hereditary defects rarely survived. Today, thanks to sanitation, modern pharmacology and the social conscience, most of the children born with hereditary defects reach maturity and multiply their kind. Under the conditions now prevailing, every advance in medicine will tend to be offset by a corresponding advance in the survival rate of individuals cursed by some genetic insufficiency. In spite of new wonder drugs and better treatment (indeed, in a certain sense, precisely because of these things), the physical health of the general population will show no improvement, and may even deteriorate."