A few months ago I got tested by 23AndMe. Here are the results:
I'm not surprised that I'm almost entirely Jewish. I look like my parents, who identify as Jews. And they look like their parents, who were also Jews. What surprised me is how good technology has gotten at this. The precision level is 0.1%, yet East Asian, Sub-Saharan and Amerindian categories are still 0%. Which they undoubtedly are in my actual genome, but I guess I expected the test to produce more random noise.
I wonder how many people of my background get more than 99% Ashkenazi. Does anybody get more than 99.5%? That could shed some light on the question of whether or not the 1.7% of my ancestry that's not Ashkenazi represents real admixture into the Ashkenazi gene pool after it was established or, alternatively, definitional fuzziness. All of this 1.7% comes from the Middle East, North Africa and Europe. I assume that it would be much easier to neatly fence off, say, the Ashkenazi and Korean genetic categories than the Ashkenazi and the "broadly Middle Eastern" one.
I've read that latest research shows us to be an almost 50/50 mix of Middle Easterners and Europeans, and that the European portion comes mostly from Italy. This makes historical sense. Jews could have come to the center of the Roman Empire to do business. Or they could have been brought there as slaves or prisoners of war (often the same thing in antiquity) after one of their failed revolts against Roman authority.
However, I don't think that in terms of personality we're more like Italians than we are like Greeks, Spaniards, Lebanese, Armenians or other Mediterranean peoples. The things that distinguish Italians from other Mediterraneans - an amazing feeling for visual beauty, a deep concern for the culinary arts - are very different from the things that distinguish the Ashekenazim from them, things like bookishness and neuroticism. Word and image, anxiety and confidence: pretty different things. So if tomorrow it turned out that the early studies were wrong and that we aren't part-Italian after all, I would not be surprised.
Another thing that recurs in the studies of Ashkenazi genetics is that there's relatively little genetic variation among us. That may well be true, but there's definitely a lot of visual variation. I have a feeling that outsiders underestimate its size because the only times they think "that guy must be Jewish" is when the guy in question looks really, really Jewish. A lot of Jews don't. I don't, yet look at the screenshot above. Based on a lifetime of observation I would say that the amount of facial variation among the Ashkenazim isn't lower than among the average Middle Eastern or European ethnicity.
23AndMe asked me hundreds of questions after I signed up with them. Do I have astigmatism, do I exercise more than once a week, have I ever had kidney stones, etc. They're obviously tabulating the responses against people's genomes. Sadly, the rules of PC would not allow them to ask folks to measure their nasal and cranial indices, orbital heights, head circumferences or anything of that sort. Lots of fascinating data is not being collected.