George Johnson is looking for an estimate of how many humans have ever lived on Earth. The answer: 108 billion.
I was stunned by the magnitude of the number. It is still common to hear that more people are alive today than have ever lived. Or an even more extreme claim: that 75 percent of everyone who ever walked the earth is living today. If the Population Reference Bureau is correct, the proportion of living to dead is only about 3 percent.
Stunning, yes, and enough to make me feel a bit constrained.