Because circumstances have changed, selective pressures have changed, and an ability to grab the half gnawed finger bone from your fellow ape-creature is less v

Because circumstances have changed, selective pressures have changed, and an ability to grab the half gnawed finger bone from your fellow ape-creature is less valuable now than it once was. In a world where the disabled can write code or whatever, they have evolutionary value. I don't disagree with the premise btw of devolution a la Idiocracy, just think your specific argument falls flat.