Bob Kosovsky wrote:
On Sun, 13 Jan 2013, IsraelP wrote:
On the other hand, another member of our family group whose mother isI've asked a question to three different statisticians, one of them not
Jewish, all of them unknown to each other. The question was concerning
Rashi, the famous rabbi who died around 1100.
The question was "how many descendants would Rashi have?"
The answer >from all three statisticians was the same: Stastically, every
European, Jewish and non-Jewish, is related to Rashi.
The two questions are completely unrelated.
When the FTDNA Family Finder indicates that you are 100% Middle
Eastern Jewish it means that each and every one of your 8 great
grandparents, or 16 great-great grandparents, had DNA that is
typical of the Jewish population. A possible answer to Israel
Pickholz's question might be that his great grandparents were
likely all Jewish, but among his aunt's great grandparents - who
reach one generation further back, there may have been one person
with non-Jewish ancestry.
The question about Rashi is very different. Going back 900 years
to the time of Rashi, we are looking at about 30 generations.
Going back that far, each and every one of us has, theoretically,
a billion ancestors. The reality is that we have far fewer
ancestors because quite a few of them overlap in our family tree
when we go that far. And besides, there weren't a billion people
in the world 900 years ago. All the clever statisticians are
saying is that *one* of our ancestors, out of the theoretical
billion, was probably Rashi. So yes, Rashi would be an ancestor
of every European, if there was sufficient mixing between the
Jewish and non-Jewish populations over those 900 years. However,
that doesn't say anything about all those Europeans being 100% or
even 1% Jewish. The autosomal DNA test used by the Family Finder
is useful for finding family relationship going back about 4 or 5
generations. None of us have measurable traces of the specific
DNA of Rashi or any other ancestor >from 30 generations ago (except
for direct male line descendants who would share his Y-DNA,
probably with a few mutations along the way).
El Cerrito, CA