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It seems that everyone has their own example of the effects of exponential growth, so here is mine:

Let us accept the biblical account that all human beings descended from one original couple, and biblical scholars' estimates of the date of creation as being 4004 BC. If every couple throughout history had exactly two children who lived to reproduce, then the population of human beings would remain stable and would never increase, since each couple would merely be replacing themselves. So let's assume that the reproduction rate of human beings has been steady throughout the history of the earth, and that couples have averaged three children per generation (who lived to reproduce again), with an average generation time of 20 years.

If the population of the earth has grown as described in this scenario, without any other constraints or disturbances, what would be the total mass (or weight) of the combined human population today, if we assume that the average human being weighs 150 pounds?

Hint #1: Use a unit of measurement greater than tons!

Hint #2

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