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How Many Ancestors

nA=2nnA=2n
(n)Number of Generations Back
(gT)Time between Generations
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The How Many Ancestors calculator computes the total number of ancestors a person or sexual reproducing animal has base on the number of generations going back.  It also estimates the approximate time span associated with those ancestors.

INSTRUCTIONS: Enter the following:

  • (n) Number of Generations Back
  • (gT) Time between Generations

Number of Ancestors (aN): The calculator returns the number of ancestors and the approximate time span (tS) in years.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

Every mammal has two biological parents.  Every generation increases the total number of ancestors by a factor of 2.  Therefore, the total number of ancestors is equal to:

  nA = 2n

where:

  • nA = number of ancestor
  • n = number of generations going back

The time span is a function of the number of generations and the average time between generations:

   tS = n * gT

where:

  • tS = Time Span of all generations
  • n = number of generations
  • gT = average time between generations


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