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The Math Behind a Family Tree: The Cruel Side of Genealogy

I have been actively working on my family’s genealogy for the past thirty-three years. In that time, I have uncovered some amazing facts and have learned more about my family than I ever thought possible. So why is it that, after all these years of hard work, I feel I have barely scratched the surface of all there is to discover?

As I have pondered on this question, I have had to come to grips with the duplicity of my my relationship with “Miss Genealogy”.

You see, I love Genealogy. From the first day I set my eyes on her, I was captivated by the hope and promise she tempted me with. And, indeed, she has been very good to me. She has inspired me; and she has opened my eyes to a greater understanding of myself. And I, in turn, have been motivated to work hard and please her with the rewards of my labor. Sadly, though, my efforts never seems to be enough to please Miss Genealogy; and she constantly reminds me of my inadequacy.

Putting my tongue-in-cheek humor aside, the reality I am trying to express about genealogy is that the more you know, the more you realize what you don’t know. The more you discover, the more missing links you find, the more family mysteries you solve, the more you realize is yet undone. Simply put, genealogy is a never ending endeavor. And the reality of this lies in what I call “the math behind a family tree”.

The simple mathematical formula of genealogy is that with each generation backwards you look, the number of ancestors waiting to be discovered doubles. Each person has two biological parents. They have double the amount of grandparents: four. They have double the amount of great-grandparents: eight. They have double the amount of great-great-grandparents: sixteen. And double begets more doubles, to the point of infinity.

And this, my friends, is the math behind genealogy. It is why I fret that my ancestor sleuthing is never going to end. Alas, all my effort will never be enough to please Miss Genealogy!!

I stumbled across this realization one day after celebrating the discovery of my first set of tenth-great-grandparents. After the euphoria of my discovery wore off, I set about to figure out how much work lie before me to find all of my other tenth-great-grandparents. I’m embarrassed to say, I couldn’t do the math in my head. Putting pen to paper, I was shocked at the size of the number.

And the answer is… (drumroll please)… 4,096! (Gulp!)

After coming to this shocking realization, the conversation in my head quickly moved on to a discussion with self as to whether the glass is half empty or half full.

The moral of the story is that genealogy can indeed be a numbers game. And if one’s motivation is simply to fill pedigree charts with names, then one’s measure of success lies in how many individuals are in his or her family tree. My challenge to genealogists, however, is to change the focus from the quantity of names in a family tree to the quality of information in a family history. That is to say, the legacy of one’s tenth-great-grandparents lies in their personalities, their triumphs and struggles, their dreams and their disappointments. Learning these things will help us discover more about ourselves. And yes, all my previous humor aside, this is what will lead to a happy and rewarding relationship with Miss Genealogy.

Suggested format for citations of this article:
Tormey, Michael. “The Math Behind a Family Tree: The Cruel Side of Genealogy”, “Michael Tormey’s ‘Legacy Blog'”, posted April 30, 2013, ( accessed [access date]).


5 Comments Post a comment
  1. Great post!

    April 30, 2013
  2. Saw your blog listed at Geneabloggers, congratulations.

    Take care,

    Moises Garza
    We Are Cousins – My personal blog about South Texas and Northeastern Mexico Genealogy
    Mexican Genealogy – Blog where I help anyone with Mexican Ancestry get started with their Family History and Genealogy.

    May 7, 2013
  3. Frederick Appleby #

    Yes I too have come to this realisation and that the chance of identifying every one of my 29xGreat grandparents is too slim to consider. So yes I go for quality and also the length of any single line. What I would also like to discover is if there is a math to identify one’s relationship with remote cousins and not just the distance to direct forebears. After all at the end of the day everything in the universe is simply a complex math problem as we know from the ancient Greeks. Frederick

    February 3, 2018
  4. Well said, Frederick!

    February 3, 2018

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