Yeah, some of it goes back to clean and unclean with the Hebrews. Unclean animals only had (have) one stomach and didn't digest their food well, supposedly making it less fit for human consumption. A horse has a less complicated stomach and digestion than a cow (they used to go by how the hoof was and cud chewing). I still won't eat ham cause pigs are so nasty, they were equated with dogs back then. Some of it is cultural. But some things I think human nature tells you don't eat. Roaches, rats, snakes. I don't like to eat bottom feeding fish, they're unclean as well. Wouldn't eat a vulture cause they're scavengers. If I was starving it would be different. Pigeon and quail eggs are more 'clean' than chickens who scavenge and will eat almost anything. It's the easily fed and raised animals that are staples, bacon and chicken eggs.