Depending on how you look at things, it has taken humanity a long time to reach this landmark, or practically no time at all. Around ten thousand years ago, there were maybe five million people on earth. By the time of the First Dynasty in Egypt, the number was up to about fifteen million, and by the time of the birth of Christ it had climbed to somewhere in the vicinity of two hundred million. Global population finally reached a billion around 1800, just a couple of years after Thomas Malthus published his famous essay warning that human numbers would always be held in check by war, pestilence, or “inevitable famine.”
In a distinctly un-Malthusian fashion, population then took off. It hit two billion in the nineteen-twenties, and was three billion by 1960. In 1968, when Paul Ehrlich published “The Population Bomb,” predicting the imminent deaths of hundreds of millions of people from starvation, it stood at around three and a half billion; since then, it has been growing at the rate of a billion people every twelve or thirteen years. According to the United Nations, it reached six billion on October 12, 1999. (A baby boy born in Sarajevo, Adnan Mević, was, for symbolic purposes, designated the world’s six-billionth person and greeted at the hospital by U.N. Secretary General Kofi Annan.) For large and slow-to-reproduce mammals like humans, such a growth curve is, to put it mildly, unusual. Edward O. Wilson has called “the pattern of human population growth” in the twentieth century “more bacterial than primate.”
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