"Simple" Math Question (to keep Namir busy)

[Chuck]

I know I've seen this discussed before, and could probably do a search to find the golden answer provided by the likes of Wikipedia) but that would take all the fun out of debate....

Let's assume there are 6 billion people alive today, and it's fairly safe to say that none were alive 100 years ago. But, in the last 100 years there has been many births and deaths of people not counted in the current 6 billion. Plus, many numerous other factors during the milleniums past have had drastic affects on population (what century saw the only MAJOR world population decline.)

So my question is...what is your best estimate of the total number of different people (homonids, bipedals, etc., your choice what to include) that have ever been born?

My knee-jerk response was triple, or about 18 billion, but I think that is woefully small. What's your best guess???

No fair looking up info on the Web.

[Allen]

your answer is in first line of the preface to Aurthur C. Clarke's '2001: a space odyssey' which out of respect for the strictest copyright conventions, I shall not post in this forum. GRIN! just kidding!

Quote:

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Behind every man now alive stand thirty ghosts, for that is the ratio by which the dead outnumber the living. - AC Clarke

---

[Chuck]

So if Arthur is "the man" then we're already down to "behind everyman stands 15 ghosts" (assuming 1960's population of about 3 billion). Pretty soon there will be only one additional ghost per person. Not a happy thought. 8(

[Gene]

The Riverworld saga by Phillip Jose Farmer also speculates on this number...depends of course on the starting date and definition of a human. :-)

It's quite an interesting series of books.

http://www.amazon.com/Your-Scattered-Bodies-Riverworld-Saga/dp/0345419677

"To Your Scattered Bodies Go is the Hugo Award-winning beginning to the story of Riverworld, Philip José Farmer's unequaled tale about life after death. When famous adventurer Sir Richard Francis Burton dies, the last thing he expects to do is awaken naked on a foreign planet along the shores of a seemingly endless river. But that's where Burton and billions of other humans (plus a few nonhumans) find themselves as the epic Riverworld saga begins. It seems that all of Earthly humanity has been resurrected on the planet, each with an indestructible container that provides three meals a day, cigarettes, alcoholic beverages, a lighter, and the odd tube of lipstick. But why? And by whom?"

[Peter A. Gebhardt]

Chuck,

you might search the internet for "Stochastic Present Value".

Think along the line of adding up a series of (say) yearly "reproduction amounts" like the PMT in TVM problems, BUT with stochastic varying PMTs AND stochastic varying (reproduction- aka interest) rates.

Usually solved by Monte-Carlo Simulation, you might also find some closed form solutions.

Best regards

Edited: 3 May 2007, 5:31 a.m.

[Namir]

Chuck,

Your assumptions are shaky. You should take into account the average lifespan of each generation (and not 100 years), which has increased especially recently. You should also take an average growth rate (which fluctuates according to the UN web site).

You can simplify things, but the result may not be relevant.

Peter's analysis is very insightful. You should follow his analysis.

Namir

[Barry Schwartz]

There is an article entitled "How Many People Have Ever Lived on Earth" by Carl Haub (available on-line). His analysis came to the conclusion (the article was written in 2002) that the number is 106 billion.

[Peter A. Gebhardt]

Barry,

Thx. for pointing to this article - although (and because) I wasn't able to retrieve it online, I started googling for other sources (out of curiosity) and found this article which does offer a simple "macro-model" which (as claimed) posseses a very high accuracy to describe the population growth since 25.000 B.C.

http://jwsr.ucr.edu/archive/vol11/number1/pdf/jwsr-v11n1-korotayev.pdf

Best regards

PS: I've just found the referenced source ...

http://www.prb.org/Articles/2002/HowManyPeopleHaveEverLivedonEarth.aspx

Edited: 3 May 2007, 6:50 p.m.