*190,000 years.
And many many factors play a roll in this, it's not like exponential population growth is exactly an easy task to perpetuate in a dispersedly populated desert land with a species that only lives for an average of 30-40 years which is so complex that without proper care, infertility, stillborns, and birth defect rates are very high.
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So scientists are willing to consider variations in the growth rate of a population but not the variation of Carbon 14 in our atmosphere... They put their variables where they want to make their equations match what they expect