How would you go about answering the question “How many people have ever lived on this planet?” If you type that into Google or an artificial intelligence chatbot, you’ll get an answer pretty quickly—usually 117 billion. That number, at least in my opinion, seems far too small. After all, the world’s population is currently estimated at 8.2 billion people. That means we make up about 7 percent of all people ever born.
The 117-billion figure includes every person who has ever seen the light of day—including those who died young. Life expectancy has increased globally over time, however. As a result, there are other strange population questions to consider. For example, a 2014 article in the Economist stated that half of all people who have ever been age 65 or older are alive today. Can that really be true? And how do you even calculate something like that?
Demographers have been asking such questions for decades. One of the biggest challenges they face is from the data: you need to know how many people have lived at different times, as well as the average life expectancy or birth rate. Such numbers are available today (though records are not always reliable) but less so for centuries past. Statistical analyses and censuses have not been routinely carried out everywhere and across all societies. Demographers must therefore rely heavily on estimates.
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And then there are a few fundamental questions to consider. What exactly is meant by “human”? Do we mean all members of the genus Homo who have walked our planet or just Homo sapiens in particular? Given the challenges, it’s astonishing that when estimating all the people who have ever lived, we are usually only presented with one…
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