It is difficult to calculate the answer to the question “How many people have ever lived on Earth.” To begin, when we first wrote this article in 1995. Homo sapiens were thought to have first walked the world around 50,000 B.C.E. New evidence suggests that modern Homo sapiens existed much earlier, around 200,000 years ago. This significant shift in our understanding of human existence prompted new calculations and expert consultations. Which results in an estimate that approximately 117 billion members of our species have ever been born on Earth.
How did we arrive at this figure? Dudley Poston Jr., a prominent demographer at Texas A&M University, extended our original analysis to 190,000 B.C.E. and estimated that between 190,000 and 50,000 B.C.E., there were approximately 8 billion births. Using Poston’s figure, we arrived at our revised estimate of 117 billion people born since 190,000 B.C.E. We also estimate that another 4 billion births will bring the total number of people who have ever lived on Earth to around 121 billion by 2050.
To be sure, calculating the total number of people who have ever lived is a combination of science and art. There is no demographic data for more than 99% of human history. Still, we can get a rough estimate of this number by making some assumptions about population size throughout human history.
What Can We Say About Prehistory and History’s Population?
Any estimate of the total number of people who have ever lived is based on three factors. First, the time humans are thought to have been on Earth. Also the average population size at different times. Then the number of births per 1,000 population during each of those times. The estimate, however, is not based on the number of deaths over any given time period.
It is difficult to pinpoint when humanity first appeared on the planet. The earliest hominins are thought to have appeared 7 million years ago. The earliest Homo species appeared between 2 million and 1.5 million years ago. According to current evidence, modern Homo sapiens first appeared around 190,000 B.C.E. Modern Homo sapiens are thought to have originated in Africa. Although the precise location has long been debated. For the first two-thirds of human history, various groups are thought to have lived in various locations across Africa.
Around 8000 B.C.E., the world population was around 5 million people. (Table 1 shows very rough figures representing averages of estimates of ranges provided by the UN and other sources.) Slow population growth over an 8,000-year period—from an estimated 5 million in 8000 B.C.E. to 300 million in 1 C.E.—results in an extremely low annual growth rate of only 0.05%. It is difficult to estimate the average global population size for this time period. Human populations in different regions most likely grew or declined in response to food availability, animal herd variability, periods of peace or hostility, and changing weather and climatic conditions.
Life Expectancy
In any case, life was fleeting. For most of human history, life expectancy at birth was probably only around ten years. Life expectancy in Iron Age France (from 800 BCE to around 100 CE) was estimated to be only 10 or 12 years. For the species to survive under these conditions, the birth rate would have to be around 80 live births per 1,000 people. To put that in context, a high birth rate today is around 35 to 45 live births per 1,000 population, and it is only observed in a few Sub-Saharan African countries.
Because of these low life expectancies, the human population has struggled to grow. One estimate of the Roman Empire’s population in 14 C.E., spanning Spain to Asia Minor, is 45 million. Other historians, on the other hand, place the figure twice as high, demonstrating how inaccurate population estimates of early historical periods can be.
By 1650, the world’s population had risen to approximately 500 million. Which a small increase from the estimated 300 million in 1 C.E. The average annual rate of growth in this period was actually lower than the rate suggested for the period 8000 B.C.E. to 1 C.E. The Black Death was one reason for the unusually slow growth. This dreaded plague did not stop in 14th-century Europe; it may have started in western Asia around 542 C.E. and spread from there. Experts believe that plague destroyed half of the Byzantine Empire in the sixth century, resulting in 100 million deaths. The difficulty of estimating the number of people who have ever lived is exacerbated by such large fluctuations in population size over long periods.
Assumptions Aid in the Estimation of Human Population History
However, by 1800, the world population had surpassed 1 billion. Now it has since continued to grow to its current 7.8 billion (our most recent estimate as of 2020). This expansion has been fueled in large part by advances in public health, medicine, and nutrition, which have reduced mortality rates, allowing more people to live well into their reproductive years.
Estimating the total number of people born necessitates determining population sizes for various points in human prehistory and history and applying assumed birth rates to each period. We begin at the very beginning—with only two people (a minimalist approach!). Although it is unlikely that humans descended from two individuals, this method simplifies our estimation.
The pattern of population growth is one complicating factor. Did it reach a plateau and then fluctuate wildly in response to famines and climate changes? Or did it continue to grow at the same rate? We don’t know the answers to these questions, despite the fact that paleontologists have proposed a number of theories. We assumed a constant growth rate applied to each period up to modern times for the purposes of this exercise. Through 1 C.E., annual birth rates were set at 80 per 1,000 population. and at 60 per 1,000 from the year 2 C.E. to 1750. By the modern period, rates had fallen below the 20s.
We account for a sizable proportion of all people who have ever lived.
According to this semi-scientific approach, there have been approximately 117 billion births since the dawn of modern humankind. Clearly, the time period from 190,000 B.C.E. to 1 C.E. is critical to our estimate. However, not much is known about the population during that time period. If we were to challenge our conclusion in any way, it is possible that our method undercounts the number of births to some extent. In the earlier period, the assumption of constant rather than highly fluctuating population growth may have understated the average population size at the time.
Given the current global population of around 7.8 billion, the revised estimate means that those alive in 2020 will account for nearly 7% of all people who have ever lived. Because we have been on Earth for about 200,000 years, that is a fairly large percentage.
