That seems like a very forced theory. By the time shellfish is bad enough to present a health risk, it smells, looks, and feels repugnant, one doesn't need a re

That seems like a very forced theory. By the time shellfish is bad enough to present a health risk, it smells, looks, and feels repugnant, one doesn't need a religious system to know not to eat it. Shellfish are susceptible to harmful algal blooms like red tide, that can make them very dangerous. Coastal foraging cultures that don't have bans on eating shellfish, instead have complex knowledge about when, where, and how to prepare and eat them. It's the same with mushrooms- cultures either universally ban them, or deeply educate everyone about them. All cultures globally with access to these foods have a system here- it's not unique to Judaism.