Fears about Earth’s burgeoning human population have long been at the back of many people’s minds. Now, it seems, as the threat of nuclear annihilation recedes from the headlines, those fears can move up to claim center stage. Moving along with the anxiety, of course, is a great deal of confusion, not the least of which is about how to recognize a population problem when you see one. Population problems are entangled with economics, the environment, and culture in such complex ways that few people can resist the temptations of unwarranted simplification. The result is a loose and widely accepted collection of myths, all of which wrap a heavy coating of fiction around a nugget of truth. During the 30 years I have spent studying population dynamics, I have become quite familiar with these myths, in all their guises. Here, in their essential form, are ten of the ones that I have encountered most often.
1. The human population grows exponentially.
In 1798 the Reverend Thomas Robert Malthus wrote that any human population, when unchecked, doubles in a certain unit of time, and then keeps on doubling in the same unit of time. For example, according to his statistics, in the English North American colonies, now the powerful People of the United States of America, . . . the population was found to double itself in 25 years.
The fact is that hardly any human populations keep doubling in the same unit of time for very long. Two thousand years ago, there were about 250 million people on the planet. It took about 1,650 years for the population to double to 500 million. But the next doubling took less than 200 years--by 1830 Earth’s human population had passed 1 billion. After that the doubling time continued to shrink: just another 100 years to reach 2 billion, then only 45 years more to get to 4 billion. Never before the twentieth century had any human being lived through a doubling of Earth’s population.
But things have begun to change. In 1965 the global population growth rate peaked at around 2 percent per year (a rate sufficient to double the global population in 35 years, if it were sustained) and then began to fall. It has now dropped to 1.5 percent per year, which yields a doubling time of 46 years. For the first time in human history, the population growth slowed, despite a continuing drop in death rates, because people were having fewer children. The myth of exponential growth misses this human triumph.
