It's not just the number of humans on the planet. Perhaps even more problematic is human activity... Not just consumption of resources, but also production of waste, including highly toxic and/or nuclear waste. How will you convince people to give up modern convinces. Very few people think about any of this. Most people are focused on their day to day needs... That is especially true for people in third world countries. One can hardly blame them. For a long time I postulated that perhaps one billion might be sustainable. Eventually I realized that there is no level of human population that is sustainable, because even if there was some magical way that we could dramatically (and painlessly) lower our numbers, it would not be long before we had marched right back to where we are now. Now I conclude that humans, my own species, is an evolutionary mistake. A catestrophic mistake!

BTW - Bravo on an exceptionally well written article.