I don’t have time to find proof right now but what I think is that our interference in human evolution while being good thing for individuals, is bad for the species as a whole. Just look at SARS. The increasingly tougher vaccines we’re injecting into our kids forces viruses to mutate and adapt faster becoming resilient to anything we can throw at them. Nature and evolution works on the basis that all living species have equal “value” and every single one plays a critical role in the living environment. Every little thing is dependent on everything else. Species mutate and adapt or die off for the good of the Earth. Humans (like any other species) are selfish and are only concerned for the survival of its own species. Nature is working and will select those species which will continue and those which will become extinct.