I don't think the Yibir are anything particularly special. They appear to be just another "low caste" Horner group. Somalis have others like Madhiban and the Tumaal:
Somalis are not very different from other Horn people in this respect. The "Beta Israel" who are not really real Jews either suffered a similar fate in Ethiopia because
they were an artisanal group. Basically, in the eyes of old traditional Horner culture if you are not a food-producer (like a farmer or pastoralist), your line of work is seen as "unclean" and "impure" and your group are usually treated like outcastes and not married by the rest of the population. Blacksmiths, tanners, stonemasons, soothsayers and "magicians"... the list goes on.
Madhiban, Yibirs and the Tumaal are such examples among the Somali people and you find very similar castes among Amharas, Tigrays, Oromos and even Omotics like the Ari which is why if you look up genetic samples on the Ari there are "Ari Cultivator" and "Ari Blacksmith" samples with a slight genetic difference between the two due to endogamy.
It's very sad because these same people are usually responsible for some of the most beautiful parts of our cultures. I mean look at these:
But the guys who crafted those would have been seen as second class humans. Xaram.
The Beta Israels' claims to Jewry, despite being taken into Israel is very questionable too. Genetic studies on both their uniparentals and autosomal DNA so far show that they have no special affinity toward Jews. In fact, their
Christian counterparts in the Amhara and Tigray regions have a stronger pull toward MENAs and Jews than they do, albeit by a very small margin. There is also the fact that these guys did not use to use Hebrew as a liturgical language at all unlike the not so far away Yemenite Jews. Instead they used Ge'ez (or sometimes their own
Agaw dialects written in the Ge'ez script) like any other Ethiopian Highlander Christian population.
I side with some scholars I've seen around but can't recall by name right now who generally think they were historically just Ethiopian Orthodox Christians practicing a unique, perhaps more old-testament focused form of the local Christianity intermingled with some local pagan elements as a result of them having been out-caste for being an artisanal group.
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One thing I find interesting though is that I too, for a long time, have thought that metallurgy likely spread to Somalis from Ethiopia possibly alongside this pseudo caste-system and that groups like the Yibir and Tumaal are the result of this spreading of skills like blacksmithing. Whether or not this came with genes being spread remains to be seen though.