Yes, there are 4 types of locust that are edible according to Kashrut, but my understanding that it's mostly for the environmental reasons - because migrating locusts causing so much damage to agriculture - the Rabbis permitted to eat them (similarly as some vegans are saying that oysters can be eaten since they're sustainable and clean the oceans).
Lately I heard another explanation by Prof. Yigal Bin-Nun[1], that when so called "Judaism" became an organized religion it simply assimilated the previously existing dietary norms and taboos. And the pork wasn't eaten in the entire area even before the first mention of the Israelites. The exception being the Philistines who brought a European pig and wild boar to Canaan. Recently there was a DNA research paper which confirmed that the wild boars in Israel are of European origins, not local ones.
So according to this theory it might be that locusts "whitelisted" by "Judaism" when the Himyarite kingdom was converted, probably because locusts were already consumed before the conversion. Of course it's only my speculation.
EDIT: yet another theory is that pork was prohibited b/c swine shares some similarity with human anatomy and thus both species can share common diseases. So it was prohibited to eat in order to prevent epidemics/pandemics. There is some mentions of this in Jewish sources, but it mostly sounds like an afterthought.
>> similarly as some vegans are saying that oysters can be eaten since they're sustainable and clean the oceans
Never heard that argument, but it seems like a misunderstanding. Peter Singer made the point that oysters have no nervous system and are therefore as plant-like as animals can come and probably non-sentient. The fact that oysters clean the oceans would also be a pretty strange argument. That's why there are so chock full of contaminants and pathogens in most places and many countries have special allowances to make them street legal when virtually any other food with the same toxin contents would be banned.
Lately I heard another explanation by Prof. Yigal Bin-Nun[1], that when so called "Judaism" became an organized religion it simply assimilated the previously existing dietary norms and taboos. And the pork wasn't eaten in the entire area even before the first mention of the Israelites. The exception being the Philistines who brought a European pig and wild boar to Canaan. Recently there was a DNA research paper which confirmed that the wild boars in Israel are of European origins, not local ones.
So according to this theory it might be that locusts "whitelisted" by "Judaism" when the Himyarite kingdom was converted, probably because locusts were already consumed before the conversion. Of course it's only my speculation.
The more traditional theory on Kashrut origins:
https://news.ycombinator.com/item?id=4493194
https://news.ycombinator.com/item?id=4493915
EDIT: yet another theory is that pork was prohibited b/c swine shares some similarity with human anatomy and thus both species can share common diseases. So it was prohibited to eat in order to prevent epidemics/pandemics. There is some mentions of this in Jewish sources, but it mostly sounds like an afterthought.
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[1] https://he.wikipedia.org/wiki/%D7%99%D7%92%D7%90%D7%9C_%D7%9...
https://www.wikidata.org/wiki/Q58348355