A long time ago I attended a talk by Paul Hawken at the Denver Museum of Nature and Science, where one of the topics was overpopulation. Paul showed a video of the globe, with population centers as lights, then put it through a fast forward from 1900 to the present. It truly took my breath away to see how lit up the globe was, and this was at least ten years ago.
I still remember one comforting thing he said. In all species, the females know instinctively how to deal with overpopulation. They will cease going into estrus, spontaneously abort or in some cases kill and even eat the young. This concept was also discussed in the story Watership Down. When the rabbit warren became overpopulated, fetuses were reabsorbed into the females' bodies before they developed and were born.
This preventive measure was observed in all different kinds of species, Hawken said. But in homo sapiens?? Do females still hold the key to avoiding disastrous overpopulation??