I honestly think we'd be better off if nobody had babies except those of us who truly felt called to having kids -- and then, if everybody was responsible about limiting the size of their families. One or two should be the norm. I don't know know what the world's optimum human population is, but I'm sure it's much less than the number of people we have now. Imagine if there were half as many of us, but everybody on the globe had a decent standard of living.