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How many people have ever lived?

The global population exploded during the 20th century, aided in part by better public health that reduced infant mortality and increased life expectancy. It now stands at around 7.1 billion. But how many people have lived during the entire time that homo sapiens have been around?

For a long time it was thought that this number was not that much larger than about twice the current population. There can be no definitive answer of course since there is no demographic data for about 99% of that total time period. But recent estimates suggest that the earlier figures were far too low and that the total number is around 108 billion.

Any estimate of the total number of people who have ever been born will depend basically on two factors: the length of time humans are thought to have been on Earth and the average size of the human population at different periods.

Fixing a time when the human race actually came into existence is not a straightforward matter. Various ancestors of Homo sapiens seem to have appeared at least as early as 700,000 B.C. Hominids walked the Earth as early as several million years ago. According to the United Nations Determinants and Consequences of Population Trends, modern Homo sapiens may have appeared about 50,000 B.C. This long period of 50,000 years holds the key to the question of how many people have ever been born.

At the dawn of agriculture, about 8000 B.C., the population of the world was somewhere on the order of 5 million. (Very rough figures are given in the table; these are averages of an estimate of ranges given by the United Nations and other sources.) The slow growth of population over the 8,000-year period, from an estimated 5 million to 300 million in 1 A.D., results in a very low growth rate—only 0.0512 percent per year.

It is interesting that the table of estimated figures gives the number of people in 50,000 BCE as just two. I wonder if some will seize on this to suggest that they must be Adam and Eve.

Comments

  1. dano says

    8/15/13
    The day Mano provided information stating the begining of the human race was started from 2 people (aka Adam & Eve). No matter what I have said or at least thought in the past about you Mano I take it all back. Welcome to the Christian I mean X-ing side!!!

  2. CGM3 says

    I wonder if some will seize on this to suggest that they must be Adam and Eve.

    Or even Adam and Steve… :-)

  3. says

    I wonder how much these calculations are affected by very high infant mortality? Those 5 million people in 8000 BCE might very well be the product of five times as many births.

  4. AsqJames says

    If the theocrats ever get one of their personhood bills passed, somebody will have to go back through the calculations and stick a few zeros on the end.

    But seriously, surely some of the disparity in estimates is accounted for by differences in what different people have included under the column in that article labelled “Births per 1,000″. One could legitimately count every baby that ever drew a single breath, those that lived for a few hours, or those that survived to 1 or 2 or 5 or 10 or 15 years. Given infant death rates in pre-modern times, such a simple methodological variation could account for huge differences in the final estimate.

  5. David Marjanović says

    Genetics is very, very clear in showing that there have never been only two people, no matter how far you stretch that term.

  6. dano says

    CGM3, unless you have some proof that two homo sapiens of the same sex can produce an offspring I believe we are still talking about Adam & Eve. :)

  7. Esketekebanka Fikilikippikiniki says

    Arthur Clarke used 100 billion in the foreword to 2001. Now I am left thinking what was the source of that estimate.

  8. sc_770d159609e0f8deaa72849e3731a29d says

    “unless you have some proof that two homo sapiens of the same sex can produce an offspring I believe we are still talking about Adam & Eve”
    Not necessarily. The point in time and the attributes we ascribe that would make one of our more remote ancestors homo sapiens, while their predecessors aren’t, is arbitrary. It’s perfectly possible that Adam & Steve (or Ada & Eve or Adam & Eve) and others all possessed these attributes and left homo sapiens descendants by mating with other members of the species and not with one another. We decide who was or was not homo sapiens; they didn’t.

  9. Mano Singham says

    As I wrote last year, genetic evidence says that any population bottleneck that occurred could not have been fewer than about 10,000 so this number 2 is clearly a mathematically convenient device, likely an extrapolation to early times of a formula.

    That high bottleneck figure has convinced some theologians to give up the idea of Adam and Eve completely, and I encourage you to do so too.

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