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Comment by searealist | Hacker News Reader

Ashkenazi Jews are not ethnically German. Genetic studies estimate them to be roughly 45% Levantine, 45% Southern European, and 10% Slavic. Germans are 100% North-Western European.

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I’ve met many, many Jews. To me visually, many (especially the stein, berg, etc) looked exactly like Germans.

Well, your hypothesis is wrong. They are not related beyond a few percent at best.

It looks like there's a mixed consensus on ancestry, but a fair bit of evidence they at least intermixed with European locals since prehistoric times [0]

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3806353/

No idea where the other guy got their %age numbers from, unless you only count specific parts of the family tree.

To be clear, that paper is not arguing Jewish ethnic groups were intermixing with European locals since prehistoric times, it is arguing that the Ashkenazi Jews (or perhaps it would be better to say: the proto-Asheknazi Jews) assimilated lots of European converts with ancestry in Europe dating back to prehistoric times.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5380316/

How do estimates of genetic origin relate to ethnic affiliation? Ethnicity is about culture, customs, and language, not genetics.

As far as genetics go, it's worth pointing out that there's a bit of question begging involved in identifying specific genetics with regional cultural groups in the first place.

You don't think people from a certain place tend to share similar genetics?

Genetics are a poor proxy for ethnicity. There are many who would even refer to the use of blood quantum (e.g. 23-and-me) to determine ethnicity as a form of race (pseudo)science.

My understanding of ethnicity on a genetic level is basically that it's the degree of relatedness above "clan", e.g., you have something of a hierarchy from: individual > family > clan > ethnicity. What's the issue with declaring some sufficiently high degree of relatedness ethnicity? Or is relatedness that diffuse not measurable?

It is not that genetic simmilarity is inherently meaninglessness. Just that it is not a good proxy for the social concepts people are generally using it to talk about.

I’m curious how they assign percentage to geographic location. For me it fails the sniff tests. Like how far back do you pick your line of ancestry (which has migrated all over the world) when you say stop and determine, this is the place 20% of my bloodline is from?

I imagine they do some sort of cluster analysis to find correlation along with self-identification. If so, then this is undeniably junk science based on junk-in junk-out statistical models (which is often the case with cluster-analysis).

I’m simply curious here, cluster analysis is the only method I can think of (other than guessing/categorizing arbitrarily).

I'd think bones from a couple hundred or thousand or ten-thousand years ago would provide a okay trail.

I don’t think the ancestry tests compare the DNA with archeological finds. If they did I wouldn’t trust it given the relatively small sample size of archeological finds with intact DNA.

The usual tests certainly don’t. But some scientific studies do: https://www.nature.com/articles/ncomms15694

I thought those were done to investigate migratory patterns, movements, and inter-connectivity of historic populations, not to establish ancestral lineage of living population, and certainly not to assign a geographical region to existing ethnic groups.

Yeah I think it's clustering and dimensionality reduction. E.g. if French people form a rough cluster in DNA space and Japanese people form another cluster, someone with a French mom and Japanese dad would show up as a data point roughly halfway between those two clusters.

I went on a little Wikipedia expedition hoping to find the methodology (and failed), but I did find an interesting (though not surprising) quote from one scientist (Adam Rutherford): “[These tests] don’t necessarily show your geographical origins in the past. They show with whom you have common ancestry today.”

So when our thread’s ancestor (pun unfortunate) says “45% Levantine” they mean they 45% of people alive today that are from that region (which includes many European immigrants). I bet this gets very messy given immigration patterns. Like which immigrants count as ancestry sample, and which don’t? For this problem I would personally use cluster analyses, however I would probably simply give up, knowing that cluster analysis would give me junk (and ultimately arbitrary) results with such noisy (and potentially skewed) data.

EDIT: The answer was right there next to this quote, in one of the aside picture for the same article[1]. They use Principal Component Analysis. Which IMO is even more fraught than cluster analysis, as you have even more control over what you want to get out of the model. If I remember correctly PCA—along with factor analyses—is used heavily in personality psychology and intelligence testing, the latter of which is very famous for radicalized pseudo science.

1: https://en.wikipedia.org/wiki/Genealogical_DNA_test#/media/F...

> I imagine they do some sort of cluster analysis to find correlation along with self-identification.

I don't think it's "some" -- I think that's 100% of it.

A lot of people think I am Mexican.

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