MINNEAPOLIS (WCCO) — Over the past 30 years, almost three-billion people have been added to Earth bring the total up to 7.7 billion. Another 2 billion are expected to be added by 2050.

So, how have we gotten so big so fast? Good Question.

The Earth’s population was at 4 million in 10,000 B.C. It hit 1 billion in the early 1800s and then skyrocketed from there.

“That’s because we’ve made so many improvements in medicine, public health and technology,” says Audrey Dorelien, a demographer and population heath research at the University of Minnesota’s Humphrey School of Public Affairs.

While birth rates have actually declined, people are living longer lives.

“Right now, the world is still growing and that’s because births are outpacing death,” says Dorelien.

For every one death, 2.5 people are born. Over the past 30 years, a significant part of that growth has come from the world’s two most populous countries, China (1.4 billion people) and India (1.3 billion people). The U.S. comes in at a distant third (330 million people).

“But that will actually change,” says Dorelien. “For the next 30 years, it’s actually sub-Saharan Africa that’s going to be the main driver.”

By 2050, it’s estimated that area will add 1 billion, half of the 2 billion expected growth.

At the same time, China, Japan and Thailand are expected to see negative population growth. North American is expected to only see 2 percent growth.

Heather Brown