What Happens When the World’s Population Stops Growing?

For most of the time that humans have existed, our ranks have grown really, really slowly. There were an estimated 4 million people on Earth in 10,000 B.C., and after the following 10 millennia, the planetwide population had only reached 190 million. Even in 1800, the total number of humans was still under 1 billion.

The climb since then—made possible by advances in medicine, sanitation, and food production—has been astounding. By 1900, there were 1.65 billion people; by 2000, there were more than 6 billion. Just two decades later, the global population sits at 7.7 billion.

But soon—or at least, soon in the context of human history—the number of people on Earth will stop growing. Based on , demographers’ best guess