Most People Have Never Been 20
Channel: vlogbrothers
Date: 2022-10-11

In which John gets curious about when the median human being lived, and along the way learns something surprising about the human story.
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Most of the population data in this video comes from the Population Reference Bureau, especially this excellent article: https://www.prb.org/articles/how-many-people-have-ever-lived-on-earth/ That's also where I learned that life expectancy in Iron Age France was 10-12.

The graphs and much of the information on life expectancy at various ages comes from Our World in Data, which is amazing. Here's their article on life expectancy over time and across communities: https://ourworldindata.org/life-expectancy

Their article on child survival and mortality statistics: https://ourworldindata.org/child-mortality

And their article examining mortality in the distant past: https://ourworldindata.org/child-mortality-in-the-past

I mostly relied on PRB info for global populations at various times, but this research summary from census.gov was also helpful: https://www.census.gov/data/tables/time-series/demo/international-programs/historical-est-worldpop.html

Here's my math for why most people have never been 20: Of the first 100 billion people who lived, at least half (the most prominent researchers in the field consider that estimate on the low end) of people died before 15. Counting the 3% or so who died between 15 and 20, that means that probably at least 53 billion of the first 100 billion people died before the age of 20. Of the most recent 10 billion who died (most of whom were born between 1800 and 1950), over 30% died before the age of 20. That takes us to a conservative estimate of 56 billion of the 110 billion people who've died so far. (2.6 billion people are CURRENTLY under the age of 20, so even if you look at the entire population of humans, it is probable that most people have never been 20--hence the title.)


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