How many people have ever existed?

CrowdScience

BBC

Science, Technology

4.8 • 985 Ratings

🗓️ 5 April 2024

⏱️ 27 minutes

🔗️ Recording | iTunes | RSS

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Summary

Today there are over eight billion people on Earth. That’s an awe-inspiring figure… but how does it compare to the vast numbers who came before us? Listener Alpha wants to know how many people have ever existed, so CrowdScience sets out to do a historical headcount.

The Population Reference Bureau in the USA estimated this number back in the 90s, and have been updating their calculations ever since. Demographer Toshiko Kaneda explains how their model works, the assumptions it makes – and the huge uncertainties around the number it comes out with.

We first need a date for when ‘humans’ first began, so Caroline travels to the Natural History Museum in London to meet human evolution expert Chris Stringer, and marvel at his collection of replica fossil skulls. Chris demonstrates how to distinguish our species, Homo sapiens, from other species like Neanderthals. When did these species first appear - and which of them count as human?

And once you know where to start the clock, how do you estimate the numbers of people alive at different points in history? For a population demographer like Walter Scheidel, it helps that some ancient civilisations kept detailed censuses, a few of which have survived to the present day. Caroline and Walter pour over one of these census fragments, and learn how to combine them with other archaeological clues to get some very rough numbers.

And finally: what does the future of our population look like? Poonam Muttreja from the Population Foundation of India discusses developments in the world’s most populous country, as well as the big demographic trends ahead for humanity.

Presenter: Caroline Steel Producer: Phil Sansom Additional Recording: Umaru Fofana Editor: Cathy Edwards Production Co-ordinator: Connor Morgans Studio Manager: Sue Maillot

Featuring: Toshiko Kaneda, Technical Director of Demographic Research, Population Reference Bureau Chris Stringer, Research Leader in Human Evolution, Natural History Museum London Walter Scheidel, Professor of Classics and History, Stanford University Poonam Muttreja, Executive Director, Population Foundation of India

Transcript

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0:00.0	Take some time for yourself with soothing classical music from the mindful mix, the Science of
0:07.0	Happiness Podcast.
0:08.0	For the last 20 years I've dedicated my career to exploring the science of living a happier more meaningful life and I want
0:14.4	to share that science with you.
0:16.1	And just one thing, deep calm with Michael Mosley.
0:19.4	I want to help you tap in to your hidden relaxation response system and open the door to that
0:25.5	calmer place within. Listen on BBC Sounds.
0:31.6	Oh, oh, oh, oh, oh,
0:35.0	Oh, oh, oh, wow.
0:37.0	Wow, who.
0:41.0	Hello, I'm Caroline Steele and this episode of Crowd Science from the BBC World Service
0:45.4	involves you and me and just about everyone else.
0:52.3	120 billion.
0:54.0	Including our listener Alpha in Sierra Leone.
0:57.0	He wrote in to ask us this.
0:59.0	There is a question that's been bugging me for a while now.
1:04.0	Can you find out or calculate the number of human beings that have lived since we first appeared on this earth?
1:17.0	All the humans that have ever existed. Nowadays, almost every country counts their population with the census,
1:22.0	so we have a pretty good idea of how many people are alive right now. It's about 8 billion. But how many people have ever stepped foot on this earth. Where do we even begin? I think it's probably best that I don't try and do this one alone.
1:48.0	Right, so I think what we have is a very good guess. This is Tashiko Canada.
1:50.0	She works at the Population Reference bureau in the USA,
1:52.8	a place where they've already tried to tackle this very question.
	...

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