How Many Ancestors

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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