

DNA ties Ashkenazi Jews to group of just 330 people from Middle Ages - wslh
http://www.latimes.com/science/sciencenow/la-sci-sn-ashkenazi-jews-dna-diseases-20140909-story.html

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PhantomGremlin
I'm no scientist, but I'm skeptical. The claims in the article are:

1) All of the Ashkenazi Jews alive today can trace their roots to a group of
about 330 people who lived 600 to 800 years ago

2) These people lived 25 to 32 generations ago, and their descendants grew at
a rate of 16% to 53% per generation

3) Today there are more than 10 million Ashkenazi Jews around the world,
including 2.8 million in Israel

I just can't believe the growth rate. It's astronomical. Especially in times
before modern medicine, with wars, plagues, pestilence. Especially considering
that the Nazis alone killed millions of Jews before/during WWII.

Also Jews were/are relatively widespread in Europe. Even before WWII there
were populations that were separated by thousands of miles. Until recently it
wasn't easy to migrate thousands of miles. There were already people in most
places, it was hard to travel, it was often dangerous to travel.

I dunno. I'm just going by intuition here, and as we know that is something
that is often (usually?) wrong when it comes to things outside of our normal
experience. But I believe that there were _considerably_ more than 330
Ashkenazi Jews in the middle ages.

~~~
maxerickson
Historically, there was nothing extraordinary about having 3-5 (or more)
children. 5 children gives you a high rate of population growth even if you
have quite some early mortality.

Also, it is a case of exponential growth, so you get a multiplier of up to
25,000 (from 1.5^25). Or 400,000 from 1.5^32. I guess it isn't really that
simple, but that explanation is at least useful for enhancing intuition.

~~~
PhantomGremlin
Fair enough. Exponential growth can be pretty amazing.

But think of it this way. Let's say the total population of Europe was
20,000,000 at some point in the middle ages in the countries from where the
Ashkenazi Jews originated (corresponding to the time that there were 330
Jews). [1] This is a very crude estimate, as the population certainly varied a
lot. So you're telling me that those 330 Jews out-competed 20,000,000 gentiles
to such an extent that, before the Nazis and WWII, there were (perhaps)
10,000,000 Jews in Europe?

That growth seems very high. My guess would be 20,000,000 people overall in
the middle ages means at least 20,000 Jews (0.1% of total).

But if there really were only 330 (really only 165 couples?) then they
certainly had a knack of "getting it done"! This implies that Jews were _much_
more adept than the general population at "survival", reproducing in each
generation regardless of all the droughts, wars and plagues.

One other explanation would be that the 330 starting number is accurate but
corresponds to an earlier period of time, maybe 2,000 years ago, not 600 to
800 years ago as the article claims.

[1]
[http://en.wikipedia.org/wiki/Medieval_demography](http://en.wikipedia.org/wiki/Medieval_demography)

~~~
maxerickson
The Ashkenazi Jews were part of the population decline:

[http://www.nature.com/ncomms/2014/140909/ncomms5835/fig_tab/...](http://www.nature.com/ncomms/2014/140909/ncomms5835/fig_tab/ncomms5835_F4.html)

So you wouldn't want to compare the ~300 to your peak population estimate.

Getting it done was very common in those times. People had lots of children.

~~~
PhantomGremlin
Ok, my fault for just reading LA Times article and not following the Nature
link. The figure you link to really makes clear the bottleneck and the
subsequent exponential growth. I'll read the Nature article and see if I can
gain a better understanding.

