World population density. Photo by Anders Sandberg, used under Creative Commons licensing.
To commemorate the United Nations Population Fund's World Population Day, which is today, we're sharing the first chapter of More: Population, Nature, and What Women Want by Robert Engelman. In it, he introduces and dissects a pair of population 'crises': depending whom you ask, the human race is desperately at risk either of overcrowding itself out of a planetary home or of dwindling away to nothing. Engelman explains why those concerned about falling reproduction rates should instead be celebrating the gains in women's ability to make their own choices about reproduction and offers an introduction to the history of birth control. Bonus: he sings and plays the guitar.