# Billions And Billions of ancestors

**URL:** <https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762>\
**Category:** Factual Questions\
**Created:** [September 10, 2003, 3:00pm UTC](https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762 "2003-09-10T15:00:35Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![asomihite](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@asomihite](https://boards.straightdope.com/u/asomihite)\
**Post date:** [September 10, 2003, 3:00pm UTC](https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762/1 "2003-09-10T15:00:35Z")

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I read Carl Sagan’s “Billions and Billions” a couple years ago, and just lately I’ve for some reason been thinking about something he said in that book. It dealt with exponential growth and talked about everyone having two parents, four grandparents, eight great grandparents, sixteen great great grandparents, and so on, and so on. It said that if each of these generations were counted as 25 years, that means that 1400 years ago there were (I can’t remember what the neumber was) something like quadrillions of people that are your ancestors. I don’t recall being satisfied with what he had to say about this. How can this be true?? What does it mean? Please, just some more info/insight onto why this is fascinating and perplexing to me.

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**Author:** ![Swampwolf](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@Swampwolf](https://boards.straightdope.com/u/Swampwolf)\
**Post date:** [September 10, 2003, 3:09pm UTC](https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762/2 "2003-09-10T15:09:10Z")

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[Voila!](http://www.straightdope.com/classics/a2_083b.html)

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**Author:** ![asomihite](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@asomihite](https://boards.straightdope.com/u/asomihite)\
**Post date:** [September 10, 2003, 4:27pm UTC](https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762/3 "2003-09-10T16:27:09Z")

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thx blessed

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**Author:** ![asomihite](https://avatars.discourse-cdn.com/v4/letter/a/848f3c/32.png) [@asomihite](https://boards.straightdope.com/u/asomihite)\
**Post date:** [September 10, 2003, 4:47pm UTC](https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762/4 "2003-09-10T16:47:23Z")

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thx blessed

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**Author:** ![Swampwolf](https://avatars.discourse-cdn.com/v4/letter/s/8edcca/32.png) [@Swampwolf](https://boards.straightdope.com/u/Swampwolf)\
**Post date:** [September 10, 2003, 4:49pm UTC](https://boards.straightdope.com/t/billions-and-billions-of-ancestors/200762/5 "2003-09-10T16:49:53Z")

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no worries. I’ve been amazed at the amount The Great Master™ has covered. Nine times out of ten, a search of His archives will turn up the answer to a question I have. The other time, a search of these very boards does the same.