an israeli water engineer writes: “Consanguineous marriage is almost unknown among Israeli Jews but prevalent among Palestinians.”

that’s probably pretty correct re. ashkenazi israeli jews, but i’m not so sure about other jews in israel.

i couldn’t find any recent data, but consang.net has the data from two studies on inbreeding amongst israeli jews, one from the mid-50s and one from the late-60s.

in the mid-50s, 1.4% of ashkenazis were married to either a first-cousin or were part of an uncle-niece marriage. on the other hand, 8.8% of sephardi jews were married to a first-cousin or were in an uncle-niece marriage.

then, in the late-60s, a study done in Petah Tiqwa found that 1.3% of ashkenazis were in a consanguineous marriage, while 14.3% of non-ashkenazi jews were in a consanguineous marriage.

unfortunately, no idea what the israeli rates for more recent years might be.

a study published in 1991 (also on consang.net) found that jews living in iran had a whopping 25.4% consanguinity rate. they’ve got first- and second-cousin plus uncle-niece marriages. so, look out israelis if you’ve got a lot of immigration from iran!

of course, jews have long been very endogamous. a study published last year looking at the genetics of different jewish populations found that:

“Individuals within each Jewish group had high levels of IBD [identical by descent], roughly equivalent to that of fourth or fifth cousins.”

so, ashkenazis are all related to each other like they are fourth or fifth cousins, iranian jews are all related to each other like they are fourth or fifth cousins, italian jews are all related to each other like they are fourth or fifth cousins, and so on. (comparable to icelanders.)

i would also guess that orthodox jews who observe all those tzniut laws are more inbred than other jewish groups. my favorite, the sheitel, is obviously a direct parallel to the muslim hijab, a practice which exists because of inbreeding. those jews, like so many muslims, must also be practicing some form of patrilineal marriage like fbd marriage.

an israeli water engineer also writes: “Consanguinity certainly increases defectous individuals but provides social stability and a sense of security.”

yes. one study from iceland showed that the sweet spot** re. cousin-marriage and fertility is third cousins, i.e. marry your third cousin to have the most offspring.

similarly, i think there must be a sweet spot re. cousin-marriage| inbreeding and having a functional society which operates in its members best interests. inbreed too much and you get clans and tribes (not to mention lots o’ genetic diseases) which make a society dysfuntional and divided; outbreed too much and you get too much individualism, another sort of dysfunctionality where each guy is out for himself.

**NO pun intended! (~_^)

update: i meant (and then forgot) to mention the most famous cousin-marrying jew of all — a. einstein. his second wife was elsa löwenthal (née einstein). that “née einstein” gives ya a clue right there. elsa was albert’s maternal first cousin AND paternal second cousin. but, they had no kids, so it really doesn’t count.

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