The controversies generated by climate science in recent years center around the human relationship with the natural world and with natural resources. This month, historian John Brooke puts that critical question in historical perspective—deep historical perspective. For most of human history, our species had to struggle to survive powerful natural forces, like climate and disease. In the past three centuries, however, things have changed dramatically: that struggle has been reshaped by the unprecedented growth of the human population—from under one billion to now over seven. John Brooke's essay forces us to ask whether our population can continue to grow given the current Malthusian pressure on resources and on the earth system itself.