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 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 peoplehave 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 billionhumans.

[ Source: http://www.prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx ]

	Year	Population
	50,000 B.C.	2
	8000 B.C.	5,000,000
	1 A.D.	300,000,000
	1200	450,000,000
	1650	500,000,000
	1750	795,000,000
	1850	1,265,000,000
	1900	1,656,000,000
	1950	2,516,000,000
	1995	5,760,000,000
	2002	6,215,000,000

Number who have ever been born	106,456,367,669
World population in mid-2002	6,215,000,000
Percent of those ever born who are living in 2002	5.8

The above estimate shows  that about 5.8 percent of all people ever born are alive today.  That’s actually a fairly large percentage when you think about it. Source: Population Reference Bureau estimates.

Number of people who have ever lived

Estimates of  “the total number of people who have ever lived” published in the first decade of the 21st century range approximately from 100 to 115 billion.

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 globalpopulation 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 ]

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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