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Archiver > Scotch-Irish > 1998-02 > 0886426473


From: <>
Subject: false premise in population calculations
Date: Mon, 2 Feb 1998 08:34:33 EST


Michael Kelly wrote:

>To:
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>Subject: Generational arithmetic
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>If none of your ancestors intermarried you would have more than a billion
>great x 28 grandparents after 30 generations. This would put you back
>around the 11th or 12th century when the world's population was only
>around 500 million, give or take a 100 million. Obviously this is an
>impossibility and there must have been lots of intermarriage.
>The world's population did not reach 1 billion until early in the last
>century.

>Michael Kelly

Mmm. Yes it is true that 2 to the power of 30 does give over a billion, But
this type of calculation is based on the premise that each person born in any
generation has two unique parents.

I think this premise is a misinterpretation of a statement by Richard Dawkins
in "River out of Eden" i.e. "All organisms that have ever lived - every animal
and plant, all bacteria and all fungi, every creeping thing, and all readers
of this book - can look back at their ancestors and make the following proud
claim: Not a single one of our ancestors died in infancy. They all reached
adulthood, and evry single one was capable of finding at least one hetrosexual
partner and of successfully copulating. Not a single one of our ancestors was
felled by an enemy, or by a virus, or by a misjudged footstep on a cliff edge,
before bringing at least one child into the world. Thousands of our ancestors'
contemporaries failed in all these respects, but not one of our ancestors
failed in any one of them."

We should be proud of their success in getting us here.

BUT:

my maternal grandparents had nine children (as did my paternal grandparents).
Each of those children had the same parents (I hope!). So, moving back a
generation from children to parents, we go from nine people to two i.e. a
DECREASE in population as we go into the past. Many families were larger than
today, but even today the basic premise in this calculation is not valid. Not
to mention war, famine, disease pestilence, barren families, etc.

David McIlveen-Wright MSc, DPhil, CEng, CPhys, MInstP, MInstE

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