NUMBER OF HUMANS THAT HAVE EVER LIVED The number of humans that have ever lived is sometimes guessed at for reasons as varied as:
Curiosity about number of "human souls" ever (in which case beliefs concerning reincarnation and status of those who die before birth change the number)
Comparison of inventions or progress per person per year (in which case adult humans who ever lived is a better measure)
Scientific evaluations about genetics and bottlenecks (in which case it is the breeding
population that matters).
Estimates of the number of human beings who have ever lived on Earth constitute an extremely large range, with low estimates around 45 billion, and the highest estimates topping out around 125 billion. Many of the more robust estimates fall into the range of 90 to 110 billion humans.
It is impossible to make anything close to a precise count of the number of human beings who have ever lived, for the following reasons:
The specific ranges of characteristics, physiological, psychological and cultural, which define a human being, continue to be a subject of intense scholarly research and debate. It is thus not possible to know just when in human evolutionary history to begin the count. Resolving these debates would require drawing a thin line between early humans and pre-humans, and in the lack of anthropological evidence, the placing of such a line is shaped by the personal interpretation of experts and remains arbitrary at best.
Even if the scientific community reached wide consensus regarding what characteristics defined the very first human beings, it would be nearly impossible to pinpoint the exact decade, century, or millennium when they first appeared. The fossil record is simply too scarce. Only a few thousand fossils of early humans have ever been found, most no bigger than a tooth or a knucklebone. While that may sound like a large number, it is truly minuscule when you consider that these few thousand bone fragments must be used to extrapolate the population distribution of millions of early human beings spread thinly across the face of the Earth.
Until the late 1700s, exceedingly few nations, kingdoms, or empires had ever performed a census that was considered to be anything more than a rough estimate. In many of these early attempts, the focus was not even on counting people, but merely a subset of the people for purposes of taxation or military service. Even with the advent of agencies like the United States Bureau of the Census, reliable census methods and technologies continue to evolve right into the twenty-first century. Even today, these reliable methods and technologies are not applied uniformly in all parts of the world. In short it has been less than two centuries that we have had anything that remotely resembles the robust statistical data that would be needed to perform a calculation regarding the total number of humans that have ever lived.
Considering the relatively small population in the early phases of human development, the first two factors are likely to be less significant than the third. Any such precise population count offered by any source is simply the numeric result of populations’ statistics, which necessarily used estimates and rough averages as their basis. While they may, if done astutely, provide us with a remote idea about thenumber of humans who have ever lived on the Earth, the margin of error should always be regarded as being in the billions, or even the tens of billions of people.
More optimistic experts, however, view the contemporary situations as ripe for rapid declines in
fertility prior to modernization. They can point to: Recent breakthroughs in contraceptive technology. Improvement methods of disseminating information. The legitimating of birth control by churches and states. The desire for small families on the part of even poorly educated populations around the world.
The Deliberate restriction of birth, either by means of post conception or preconception controls, is an aspect of human culture that appears to be common to all societies.
In the underdeveloped areas today, declines in morality are not normally the product o broad social changes, but they are much more efficiently being affected by the application o medical technology.
On the other hand, the reduction of morality would appear to be a necessary but not sufficient cause for widespread fertility reduction.
In Europe the gradual reductions in morality that occurred in the last two centuries were a consequence of such broad social changes as the agricultural, industrial, and scientific revolutions and the improvement of socioeconomic conditions. These general forces directly affected not only morality but fertility probably by allowing the perception of costs and benefits of children.