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Calculating the answer to the question “How many people have ever lived on Earth?” is complicated. To begin with, when we initially wrote this article back in 1995, “modern” Homo sapiens (that is, people who were roughly like we are now) were thought to have first walked the Earth around 50,000 B.C.E. Discoveries now suggest modern Homo sapiens existed much earlier, around 200,000 B.C.E. This major change in our understanding of human existence spurred new calculations and consultations with experts, resulting in an estimate that about 117 billion members of our species have ever been born on Earth.
How did we reach this number? Dudley Poston Jr., a prominent demographer at Texas A&M University, extended our original analysis to 190,000 B.C.E. and produced an estimate of around 8 billion births between 190,000 B.C.E. and 50,000 B.C.E. Taking Poston’s number into account, we came to our revised estimate of 117 billion people born since 190,000 B.C.E. We also estimate that by 2050 another 4 billion births will increase the number of people who have ever lived on Earth to about 121 billion.
To be sure, calculating the number of people who have ever lived is part science and part art. No demographic data exist for more than 99% of the span of human existence. Still, with some assumptions about population size throughout human history, we can get a rough idea of this number.