ABSTRACT
Until about ten thousand years ago, when the agricultural revolution began, the global population of human beings probably numbered a few million. Settled agriculture allowed population to start rising steadily, but very slowly, so that by AD 1 it probably numbered 200–300 million. It reached one billion around 1800, and two billion some time before the outbreak of the Second World War. The four billion mark was reached in 1960 and global population is currently around 6.7 billion (Livi-Bacci 2001). 1 It has perhaps always been possible to imagine a global population of human beings, to describe it, albeit in such rudimentary terms, and even attribute different qualities and behaviour to it. The concept of the human species is a very old one, of course, and one which contemporary biology gives an ever more specific understanding and meaning to. However a specifically demographic understanding of the global human population, understood as an integrated population system, has until very recently never been more than a strictly theoretical proposition.
