The Apostle Paul taught that which was written in the Old Testament was given for people’s instruction for salvation and right-living—this includes all the laws (ceremonial, civil, governmental, and natural) given to the Israelites. Bearing in mind that this was also an agrarian society, it is no wonder many of the statutes seem ridiculous to people who think eggs grow in cartons and fruit grows at the back of supermarkets.
Likewise, when it comes to hygiene, the Israelites did not have sewage treatment plants, so they were given a law about ablutions. Also when it came to eating shellfish, this was probably designed to guide people away from being poisoned because they ate something that filters pollution and is contaminated with disease.
The Laws Of God Are Nonsense To Those Who Think They Are Smarter Than He Is