How many people have lived in all of human history?

Large CrowdWithout access to a time machine, a large notepad and a lot of time, it’s difficult to know exactly how many people have ever lived. Even in the absence of this technology, answering this question is very difficult because accurate population records have only became common in the last few centuries.

Nevertheless, people have tried. Carl Haub a senior demographer at the Population Reference Bureau attempted what has been described as a “semi-scientific approach” to guesstimate our total historical population up to the year 2011. Haub begins his estimate assuming that Homo sapiens first walked the earth in roughly 50,000 BC. Haub uses an estimated birth rate to calculate the population growth between various points throughout history. Today, the annual birth rate stands somewhere around 19 births per 1,000 people (Haub used 23 in his study). But during the very early human history (50,000 B.C. to 1200 A.D.), there were a lot more babies born: Haub uses a birth rate of 80 births per 1,000 people for these earlier parts of history. This number is very high by today’s standards (a high birth rate would be 45 or 50 births per 1,000 people and is seen in only a few African countries), it is still probably an underestimate. The infant mortality rate during humanity’s very earliest days is thought to be at least 500 infant deaths per 1,000 people according to Haub; this means that an exceptionally large birth rate would be required to ensure the survival of the human race. Times used to be very hard indeed.

While far from perfect, Haub’s final figure calculates the total number of humans to have ever lived on the earth as 107.6 billion; although it is now widely acknowledged that the total number may be even higher. And given that the world population in mid-2011 was 6.9 billion we can expect Haub’s answer to still be fairly accurate in 2014 (it is 7.3 million today).

Of course, Haub is not the only one to attempt to answer this question; a different method used to estimate the total number of humans to have ever lived gives a much lower answer of 45 billion. These two answers differ by quite a lot because the latter method has Homo sapiens walking on the earth 200,000 years ago and makes its calculations based on the average human life span throughout history, rather than the birth rate. The scientific community regard Haub’s estimate to be more reliable, although the assumptions Haub makes are still up for debate.

It is unlikely that we will never have a truly accurate calculation for the number of people who have ever lived. Fossil records have helped us get a better grasp of when humans first existed – and continued discoveries will help us get a more accurate picture of human history. Perhaps the only way to truly know the answer is to invent a time machine… although, to be honest, I can think of better uses for a time machine!

Photo Credit: James Cridland via Compfight cc

Article by Nathan Beal

November 11, 2014

Nathan is currently in the throes of a PhD in Computational Chemistry at the University of Manchester. When he’s not behind a computer, he’s outside enjoying the sights of the city. A fan of The Walking Dead, he has a strange apathy to all things football-related.

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