RENEE MONTAGNE, host: Today, somewhere in the world a newborn is nudging the Earth's population to seven billion. That's according to a U.N. estimate. Demographers really don't know when or where that baby will be born, but the U.N. is using today to mark symbolically the dramatic change in the population. As part of MORNING EDITION's series Seven Billion and Counting, we'll explore the significance of the number.
STEVE INSKEEP, host: In a few minutes, we'll hear how two different countries are dealing with population growth. One of them is China, the world's most populous nation. The other is South Sudan and sub-Saharan Africa, where the population is expected to triple by the end of this century. First, let's go back in time - way back - to explore how we got to where we are today. Here's NPR's Adam Cole.
ADAM COLE: A thousand years ago, the world was a lot less crowded. There were only about 300 million people. That's the current size of the United States, a tiny fraction of the seven billion we have now. Let's say that one voice represents 100 million people. We'll take one voice from Europe...
UNIDENTIFIED MAN #1: (Foreign language spoken)
COLE: One from South Asia.
UNIDENTIFIED WOMAN: (Foreign language spoken)
COLE: And a third voice from China.
UNIDENTIFIED MAN #2: (Foreign language spoken)
COLE: Even back then, China and India were the most populated regions in the world. OK, so here we are in the 11th century with our three voices. How do we get from that 300 million people a thousand years ago to the seven billion people we have now? We have to travel forward in time at about 10 years per second.
(SOUNDBITE OF CLOCK TICKING)
COLE: In just five seconds, we've already passed through 50 years. The population is growing, but very, very slowly. Women are having lots of children...
(SOUNDBITE OF BABIES CRYING)
COLE: ...but most of these children die before they're old enough to start families of their own. If we fast forward to the 18th century, we'll reach 900 million people. And in 1804 we'll hit our first billion.
(SOUNDBITE OF BELL RINGING)
COLE: OK. Let's stop the clock for a moment. Things are about to get crazy. We're entering an age of better medicine and better agriculture, and that means lower death rates. Women are still having lots of children, but now most of those children are surviving to have children of their own, and their children are having even more children. You can see where this is going. OK. Let's start up again. We'll hit our second billion in 1927.
(SOUNDBITE OF BELL RINGING)
COLE: And then things really take off.
(SOUNDBITE OF BELL RINGING)
COLE: There's three billion.
(SOUNDBITE OF BELL RINGING)
COLE: Four billion.
(SOUNDBITE OF BELL RINGING)
COLE: Five billion.
(SOUNDBITE OF BELL RINGING)
COLE: Six billion.
(SOUNDBITE OF BELL RINGING)
COLE: Seven billion. Seven billion people - over five billion of them added in the last 100 years. It's easy to see that the planet has gotten pretty crowded pretty fast, but it's not so easy to predict future growth or understand how this population explosion might affect each of us. Adam Cole, NPR News.
MONTAGNE: And to see a really cool video on how the world came to have seven billion people, go to our website, NPR.org. Transcript provided by NPR, Copyright National Public Radio.