The world's population is growing at an unsustainable rate. From a baseline ?gure of one billion in 1800, global population is predicted to exceed nine billion by 2050 and 87. 8% of this growth will be localized in less developed countries. Such uneven population growth will yield a harvest of poverty, malnutrition, disease and en- ronmental degradation that will affect us all. Amongst the complex mixture of political, social, cultural and technological changes needed to address this issue, the development of improved methods of fertility regulation will be critical. The inadequacy of current...