24 April 2018

An astonishing rise in the number of humans

Posted by Callan Bentley

One interesting thing about reading T. rex and the Crater of Doom, by Walter Alvarez in 2018 is the change in world population since it was first published in 1997. In explaining to his readers how to think about measurements in “parts per billion,” Alvarez explains his mental shortcut to appreciating those numbers. He says something along the lines of “since there are 5 billion people in the world, a measurement of 3 parts per billion is a proportion equivalent to 15 people out of the world’s population.”

The global population just two decades later has increased by 50%. It’s almost 7.5 billion today. It’s astonishing how quickly this useful mental calculation has become outdated, and more to the point, how rapidly the human population on this planet is swelling. I was a single year out of college when Alvarez’s book first came out. Twenty years later, my life has trundled along its fairly predictable arc, with family and career and whatnot. And in that short time, there have been so many births, and so many more people staying alive who might otherwise have died, that when I finally get the motivation to pick up the book and read it, and I find that this particular statistic has gone stale. There are now 3 people kicking around for every 2 who I shared the planet with then. That’s really kind of amazing.

There are more people on Earth today than ever before. And tomorrow there will be even more.