With better medical technology and welfare states, the quality of your genes have a less significant effect on whether you survive to pass on your genes. Only extremely harmful mutations are weeded out. Humanity has built everything it's accomplished on the ideas and knowledge of the previous generation. I'm claiming that the contribution an invidual makes to the growing database of ideas has a greater effect on the development of mankind, than the genetic material passed on through children. A large part of this is passing on your ideas to your children through their ubringing. How much has our gene pool evolved in the last few thousand years? How much has our society evolved in that same time?