Web Bit 28-3: The Human Population Is Growing Exponentially
By Jennie Dusheck
Before the end of the last ice age, about 10,000 years ago, the world population of humans consisted of about 5 million people, who supported themselves by gathering fruits, roots, and leaves and by hunting animals. Every region probably contained a fairly constant population, with deaths balancing births.
Then, at the end of the ice age, some 8000 to 10,000 years ago, humans invented agriculture, which permitted them to reproduce faster than ever before. The human population began a population explosion that continues today. From the invention of agriculture until 2000 years ago, the human population doubled almost 5 times to about 75 million people. At that time, as today, most of the world's population lived in China and India.
In the next 1800 years, the world population began doubling faster and faster, reaching 1 billion in 1800, 2 billion in 1930, and 4 billion in 1975. Recently, world population growth has begun to slow. The world population stands at just over 6 billion people, with an annual rate of increase of about 1.25 percent. Today, instead of 87 million more people every year, as in 1989, we have "only" 75 million more people per year. Why did human populations soar after 1800? In the 19th and 20th centuries, closed sewers, chlorinated water, refrigeration, vaccines, and antibiotics reduced the death rate dramatically, first in the industrialized countries of western Europe, then, country by country, in other industrialized areas of the world. After World War II, death rates began to decline in the rest of the world as well.
Fortunately, after death rates declined in industrialized countries, birth rates soon followed. Even in most developing nations, birth rates are now beginning to decline. Twenty-five years ago, the average Mexican family had 7 children. Today the average is 2.5 and government officials are aiming for 2.1. Worldwide, the annual rate of increase has now declined from a high of 2.2 percent in 1962 to 1.25 percent in 2000. Demographers predict that the annual rate of increase will continue to decline through the next century to less than 0.5 percent in 2050. But even then, the population will still be growing, just not as fast.