Re: 20% of the Iberian peninsula's population has Sephardic Jewish Ancestry

X-No-archive: yes
I'm not a sephardic expert, but I'd like to make just a couple of small
comments. The article says: "assuming no in-breeding, he would have had
more than one million living ancestors in a.d. 1500". i would
suggest that, at 20 years per generation, that would be 25 generations,
and therefore he would actually have 2^25 (33,554,432) possible distinct
ancestors with no in-breeding. it should have said more than 30 million.
(for reference, the current population of Spain is only about 40 miilion.)

This leads me to question the validity of the study's conclusion - it is
virtually impossible that only 20% of a population could have common
ancestry after 25 generations, if interbreeding was possible. (even if it
wasn't permitted, humans seem to find ways to get around the rules.)
and to test his hypothesis, the author should have also tested known
sephardic populations for the same DNA markers.

One other limitation of this study is that it only looked at y
chromosomes, which means that it only reflects strictly patrilineal descent.
For a study of Jewish ancestry, this is probably a flawed approach,
since Judaism follows matrilineal lines (at least it did, unequivocally,
in 1500), and it's reasonable to assume that conversos and crypto-jews
would have retained such a custom, and selected marriage partners
matrilineally. (and there is anecdotal evidence that they did.) So a
similar study of x chromosomes might expect to find a much higher
correlation.

........ tom klein, toronto

ps. for an article touching on jewish ancestry, i really wish the author
had used "ce" instead of "ad" - not the most tactful choice.

There's an interesting article in the New York Times that reports on a
DNA study that shows that 20% of the Iberian peninsula's population has
Sephardic Jewish ancestry:
http://www.nytimes.com/2008/12/05/science/05genes.html

I wondered what the Sephardic experts on this list had to say about the
article.

MODERATOR NOTE: Discussions of DNA applications to Jewish
genealogy sbould be taked to the DNA List. Whilst critiques of
scientific studies are outside the scope of this list, the general
questions raised are of wider interest, i.e., what can one conclude
about relative sizes of subpopulations at one time in history based
on studying their descendants at a later date.

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