This paper provides a personal perspective on the rich discussions at the Bixby Forum. The size, rate of growth and age structure of the human population interact with many other key factors, from environmental change to governance. While the details of future interactions are sometimes difficult to predict, taken together they pose sombre threats to a socially and economically sustainable future for the rich and to any realistic possibility of lifting the world's bottom two billion people out of poverty. Adaptive changes will be needed to cope with an ageing population in countries with low fertility or below, but these are achievable. More worrying, continued rapid population growth in many of the least developed countries could lead to hunger, a failure of education to keep pace with growing numbers, and conflict. The assumption that the demographic transition from high to low birth rates occurs as a result of exogenous social and economic forces is being replaced by a clearer understanding of the many barriers that separate women from the knowledge and technologies they need to manage their childbearing within a human rights framework. The forum ended with a clear consensus that much more emphasis needs to be given to meeting the need for family planning and to investing in education.