The world population hit 7 billion on Monday, according to United Nations Population Division estimates*.
Discussions about whether our current rate of population growth is sustainable have become timely again. But rather than just looking toward the increasingly hot and crowded future — to borrow from the title of Thomas Friedman’s famous book — let’s take a moment to look back at the past two centuries of population growth, because it’s easy to forget how remarkable a time period we’re living through.
In last Monday’s edition of The New York Times, mathematical biologist Joel E. Cohen succinctly described the growth in world population since the 19th century:
The first billion people accumulated over a leisurely interval, from the origins of humans hundreds of thousands of years ago to the early 1800s. Adding the second took another 120 or so years. Then, in the last 50 years, humanity more than doubled, surging from three billion in 1959 to four billion in 1974, five billion in 1987 and six billion in 1998. This rate of population increase has no historical precedent.
When the population meter ticks up at such pace, it’s almost inconceivable that at one point our entire species risked extinction. (It’s a similar wonderment to looking at the United States’ national debt clock and remembering that just 10 years ago, we ran budget surpluses.)
Eight years ago, researchers at Stanford University and the Russian Academy of Sciences revealed that humans, threatened by conflict, disease and environmental disasters, were once on the brink of being wiped off the planet. The total human population, the researchers estimated, dropped to 2,000 — enough to fit into your high school gymnasium.
Humans appeared as a distinct entity some 195,000 years ago, but only around 120,000 years ago did we appear in significant numbers, living in East and North Africa and starting to spread to the Middle East and South Africa. Fossils and archaeological records of humans between 80,000 and 50,000 years ago are much rarer, and it was during that period that our species faced extinction.
Around 10,000 years ago, the transition from hunter-gatherers to agriculturalists ignited an accelerated growth in the human population. Instead of searching for food, we started creating it — our first major triumph over nature.
But throughout these periods of monumental change, the median life span of humans remained fairly constant. By looking at skeletons, particularly their teeth, archaeologists have determined that humans lived to their thirties and low forties. Only in the last two centuries have humans grown much older than that.
We know we’re living in times of unprecedented technological progress and global interconnectedness — that’s the flat part of Friedman’s “Hot, Flat, and Crowded.” Never have we had such influence over nature, for better or for worse. When a simple question — how different life would be without a computer, for example — makes us place today in historical context, the time frame we picture usually spans decades.
Rarely do we go back further than the Industrial Revolution. And with good reason. The Industrial Revolution was a seminal period that set in motion two and a half centuries of sustained growth in global income, standards of living, population and life expectancy.
Thanks to the ensuing development, most societies have increased their life expectancies dramatically. Angola, for example, still has a life expectancy at birth of 37.5 for men and 39.5 for women, but Japan’s men and women expect to live more than twice as long. The world’s average life expectancy is 68.9 years, according to the World Bank. This number partially explains why 7 billion people inhabit the earth today.
In the coming years, the limit to growth Malthus predicted in 1798 may finally bear out as our finite resources — even stretched to its limits by technological progress and better allocation — curb further population growth. We’re already seeing slower population growth due to declining fertility rates. Reaching the next billion is expected to take longer than this last one.
A dramatic slowdown would mark a historic inflection point in the trajectory of our population growth. Rather than us catching up to nature, like the dawn of agriculture 10,000 years ago, nature will have finally caught up to us.
When considering the astounding changes that have taken place since the Industrial Revolution — going back beyond Facebook, the Internet, electricity and Watt’s steam engine — if you look at the really big picture, these are extraordinary times. The number of people on this planet is a reminder of that.
*Correction: The United Nations didn’t name a single baby the world’s seven billionth person, as originally stated in the lede. Danica Camacho is actually among many babies the UN gave that title to.