Scientists originally believed that homo sapiens first appeared at about 50,000 B.C.E. However, researchers later concluded they may have existed as early as 200,000 B.C.E. Apparently, in 190,000 B.C.E. two people lived on the earth. By 8000 B.C.E., the birth count totaled 5 million people.
It took about 8,000 years for the earth to reach a population of 300 million people. This measured a growth rate estimated at .05 percent per year. Scientists calculate populations according to climate and weather studies, possible availability of animals and food, and peace or war. They may never come up with an exact number but base it on these variables.
By 1850, more than 1.2 billion people had lived on the earth. This started a birth rate of greater than 1 percent. By 1950, this number had just about doubled, totaling more than 2.5 billion people at a birth rate of greater than 2 percent. In 1850, however, the number of births per 1,000 people declined by about half of what this number per 1,000 was in 190,000 B.C.E. Couples began having less children, but it still didn’t stop the rapid population increase.
The number of people living in 1995 more than doubled since 1950. By 1995, the birth rate climbed to 5.1 percent and the world population totaled more than 5.7 billion. The Baby Boom starting in the mid-1940s after World War II to the mid-1960s caused this population jump. Economic prosperity allowed for marriage and “baby making” not made possible during wartime.
From 2011-2020, the world population experienced the opposite effect that occurred in the 1950s. In the United States, for example, 2010-2011 had one of the lowest population growth rates at .73 percent since before the post-war Baby Boom.
The Recession of 2008, which started with home values plummeting toward the end of 2006, contributed to this. With more people losing their homes than in preceding years, not many people were thinking about having children. By 2011, infertility rates increased, probably because they now were past childbearing age.
Limited evidence makes it difficult to count the number of humans who ever lived before homo sapiens born as early as 190,000 B.C.E. However, Dudley Poston, Jr. at the Texas A&M University facilitated studies that concluded an approximate calculation. Researchers believe that about 117 billion of modern humans have lived on Planet Earth.
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Sources: https://pubmed.ncbi.nlm.nih.gov/12288594/ https://www.prb.org/articles/how-many-people-have-ever-lived-on-earth/ https://www.brookings.edu/blog/up-front/2011/12/28/2011-puts-the-brakes-on-u-s-population-growth/