Anthropologists debate when our first ancestors appeared. For our purposes, we do not have a go that far back in time. We might begin at the end of the last Ice Age, about 13,000 years ago, when humans on all continents were still living as hunter-gatherers, or 12,000 years ago with the first signs of agricultural settlements, or 7,000 years ago with the first indications of urbanization. For most of the thousands of years since then, population growth has been close to zero, with annual births roughly offsetting annual deaths. Opportunities for human survival slowly inproved, and by 1 C.E. the world’s population is estimated at about 230 million. To gain some perspective on this number, today Indonesia by itself has population size.