Assuming that we start counting from about 50,000 B.C., the time when modern Homo sapiens appeared on the earth (and not from 700,000 B.C. when the ancestors of Homo sapiens appeared, or several million years ago when hominids were present), taking into account that all population data are a rough estimate, and assuming a constant growth rate applied to each period up to modern times, it has been estimated that a total of approximately 106 billion people have been born since the dawn of the human race, making the population currently alive roughly 6% of all people who have ever lived on planet Earth. Others have estimated the number of human beings who have ever lived to be anywhere from 45 billion to 125 billion, with most estimates falling into the range of 90 to 110 billion humans.
An estimate of the total number of people who have ever lived was prepared by Carl Haub of the Population Reference Bureau in 1995 and subsequently updated in 2002; the updated figure was approximately 106 billion. Haub characterized this figure as an estimate that required “selecting population sizes for different points from antiquity to the present and applying assumed birth rates to each period”. Given an estimated global population of 6.2 billion in 2002, it could be inferred that about 6% of all people who had ever existed were alive in 2002.
In the 1970s it was a popular belief that 75% of all the people who had ever lived were alive in the 1970s, which would have put the total number of people who ever lived as of the 1970s as less than the number of people alive today. This view was eventually debunked.
The number is difficult to estimate for the following reasons:
* The set of specific characteristics that define a human is a matter of definition, and it is open to debate which members of early Homo sapiens and earlier or related species of Homo to include. See in this regard also Sorites paradox. Even if the scientific community reached wide consensus regarding which characteristics distinguished human beings, it would be nearly impossible to pinpoint the time of their first appearance to even the nearest millennium because the fossil record is simply too sparse. However, the limited size of population in early times compared to its recent size makes this source of uncertainty of limited importance.
* Robust statistical data only exist for the last two or three centuries. Until the late 18th century, few governments had ever performed an accurate census. In many early attempts, such as Ancient Egypt and in the Persian Empire the focus was on counting merely a subset of the people for purposes of taxation or military service.[108] All claims of population sizes preceding the 18th century are estimates, and thus the margin of error for the total number of humans who have ever lived should be in the billions, or even tens of billions of people.
* A critical item for the estimation is life expectancy. Using a figure of twenty years and the population estimates above, one can compute about fifty-eight billion. Using a figure of forty yields half of that. Life expectancy varies greatly when taking into account children who died within the first year of birth, a number very difficult to estimate for earlier times. Haub states that “life expectancy at birth probably averaged only about ten years for most of human history”[106] His estimates for infant mortality suggest that around 40% of those who have ever lived did not survive beyond one year. [ Source: http://en.wikipedia.org/wiki/World_population ]
* Robust statistical data only exist for the last two or three centuries. Until the late 18th century, few governments had ever performed an accurate census. In many early attempts, such as Ancient Egypt and in the Persian Empire the focus was on counting merely a subset of the people for purposes of taxation or military service.[108] All claims of population sizes preceding the 18th century are estimates, and thus the margin of error for the total number of humans who have ever lived should be in the billions, or even tens of billions of people.
* A critical item for the estimation is life expectancy. Using a figure of twenty years and the population estimates above, one can compute about fifty-eight billion. Using a figure of forty yields half of that. Life expectancy varies greatly when taking into account children who died within the first year of birth, a number very difficult to estimate for earlier times. Haub states that “life expectancy at birth probably averaged only about ten years for most of human history”[106] His estimates for infant mortality suggest that around 40% of those who have ever lived did not survive beyond one year. [ Source: http://en.wikipedia.org/wiki/World_population ]
Estimated world population at various dates (in millions)
Source: http://en.wikipedia.org/wiki/World_population
| Year | World(in millions) |
|---|---|
| 70,000 BC | < 0.015 |
| 10,000 BC | 1 |
| 9000 BC | 3 |
| 8000 BC | 5 |
| 7000 BC | 7 |
| 6000 BC | 10 |
| 5000 BC | 15 |
| 4000 BC | 20 |
| 3000 BC | 25 |
| 2000 BC | 35 |
| 1000 BC | 50 |
| 500 BC | 100 |
| AD 1 | 200 |
| AD 1000 | 310 |
| AD 1750 | 791 |
| AD 1800 | 978 |
| AD 1850 | 1,262 |
| AD 1900 | 1,650 |
| AD 1950 | 2,519 |
| AD 1955 | 2,756 |
| AD 1960 | 2,982 |
| AD 1965 | 3,335 |
| AD 1970 | 3,692 |
| AD 1975 | 4,068 |
| AD 1980 | 4,435 |
| AD 1985 | 4,831 |
| AD 1990 | 5,263 |
| AD 1995 | 5,674 |
| AD 2000 | 6,070 |
| AD 2005 | 6,454 |
| Jul. 1, 2008 | 6,707 |
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