Including those living today, approximately how many human beings have ever lived?

Dear adamat6am-ga,

The calculation for this depends on the date commenced, how many years
is a generation, and the methodology used.

This research by the Population Reference Bureau is for 2002 and it
estimates that 106,456,367,669 people have been born since 50,000 B.C.
http://www.prb.org/Template.cfm?Section=PRB&template=/ContentManagement/ContentDisplay.cfm&ContentID=7421

The question was previously asked on Google Answers and these other
sources were quoted.
http://answers.google.com/answers/threadview?id=337411

Figures up to 1950 calculated by different sources appear at 
http://www.census.gov/ipc/www/worldhis.html

United Nations, 1999, The World at Six Billion, Table 1, "World Population From
Year 0 to Stabilization"
http://www.un.org/esa/population/publications/sixbillion/sixbilpart1.pdf

"Most studies place the total number of human beings to have ever
lived at 60 billion to 120 billion"
source: geography.about.com
http://geography.about.com/library/faq/blqzalivetoday.htm

I have also found this computation; the starting point for this
research is 1,000,000 BC.
"If one divides by 25 as an estimate of average lifespan, one
estimates that 96,100,000,000 people have lived on the earth. "
http://www.math.hawaii.edu/~ramsey/People.html


I hope this answers your question. If it does not, or the answer is
unclear, then please ask for clarification of this research before
rating the answer. I shall respond to the clarification request as
soon as I receive it.
Thank you
answerfinder

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