Theory:   pork, ham, and other products of the pig were probably put off limits because people often got sick when they ate them. Back in those days, they didn't know about parasites and trichinosis, which can be avoided simply by making sure the meat is well cooked. If people consistently got sick after eating a particular thing, to these folks it meant that it must be something God didn't want you to eat. God took a lot of the rap for sheer ignorance and pure happenstance back in those days, and there are primitives living today who are still into that bag.

With no refrigeration back in Biblical times, in warm climates such as the Eastern Mediterranean, Red Sea, Persian Gulf, etc., shellfish spoiled very quickly, and spoiled shellfish can make you urp up your sandals and possibly even kill you. Thus, God's wrath.

I love seafood, both the free-swimming kind and all kinds of shellfish. If God doesn't like shrimp, crab, lobster, clams, mussels, etc., I'll have His/Her share, thank you. . . .

Don Firth
(I love my wife, but oh, you squid!!)