Islam, Judaism, and Hinduism all have foods that their adherents are not supposed to eat. I'm going to frame this question in terms of Judaism, which is the one I know most about, but I'm interested in this in terms of any and all religions.

For Jews, kosher rules are extensive. No meat from an animal that doesn't have both split hooves and chew its cud, so while sheep, goat, and cattle are ok, there's not a lot beyond that. Only a select few birds are OK, and any seafood needs to have scales and fins - which rules out all shellfish. Beyond that, the animal needs to be slaughtered according to set rules, and after slaughter, only certain PARTS of the animal are ok (no kosher filet mignon or sirloin).

Now, I have no idea how these rules evolved over the millenia, but Jewish dietary rules are pretty restrictive. It's not so difficult to manage to get enough food in modern times, but how did such restrictive rules arise in the first place? Was there such an extensive food surplus in the ancient middle east that people had enough calories they were all right ignoring so many food supplies that neighboring peoples ate freely?