Re: [asa] Two questions...Ayala's article

On Wed, 25 Feb 2009, Preston Garrison wrote:

>> I don't agree Dick. Any number of studies have shown that every living
>> person alive today can trace his or her ancestry back to a common ancestor
>> who lived only a few thousand years ago, though obviously this person was
>> not the only person alive at the time, nor will most of us have inherited
>> genes directly from that person. See, e.g., Rhode, On the Common Ancestors
>> of All Living Humans
>> (<http://tedlab.mit.edu/~dr/Papers/Rohde-MRCA-two.pdf>http://tedlab.mit.edu/~dr/Papers/Rohde-MRCA-two.pdf);
>> Chang, Recent Common Ancestors of All Present-Day Individuals
>> (<http://www.stat.yale.edu/~jtc5/papers/Ancestors.pdf>http://www.stat.yale.edu/~jtc5/papers/Ancestors.pdf).
>> A focus on "bloodlines," I think, is archaic -- that's a scientifically
>> meaningless term. A focus on the coalescence of genes, I think, is foreign
>> to the Biblical text and unproductive. The focus ought to fall, I think, on
>> geneology, which is what the papers referenced above discuss.
>>
>> David W. Opderbeck
>> Associate Professor of Law
>> Seton Hall University Law School
>> Gibbons Institute of Law, Science & Technology
>
>
> There's really supposed to be a common ancestor in the last few thousand
> years for everyone in a remote tribe in the Amazon and for every Australian
> aborigine? Is this a statement about how thoroughly the modern world has
> penetrated every corner of the planet?
>
> Again, am I missing something?
>

I first learned about this several years ago from Glenn Morton on this
forum. I haven't taken the time to read the papers, but my impression was
that the conclusion was based on the observation that any individual has a
lot of ancestors only a few generations back. Likewise most individuals
who have descendants have very many after a few generations. Thus even
taking into account that not all the ancestors in such a calculation are
distinct and that descendants may mate with each other, it was concluded
that one did not have to go back to a time when the human population was
extremely small to find a common ancestor. Glenn pointed out that this
didn't take into account that some populations have apparently been
isolated from everyone else until quite recently.

Here is a tangentially related question: Knowing that there must have been
not infrequent intermarriage in the past, how many of us might be
descendants of Abraham and not even know it?

Gordon Brown (ASA member)

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Received on Wed Feb 25 23:53:32 2009