The law is often stupid or silly, and nowhere is that more often true than in the arena of food.
For example, did you know that the tomato is a vegetable and not a fruit?
That's wrong you say? Tell it to the U.S. Supreme Court which, in an 1893 case entitled Nix v. Hedden, ruled that the tomato was a vegetable under U.S. customs law.
And what of other dietary laws and restrictions?
Though a great deal of paliver has been spent on why one religion or culture bans one food (such as cow) but not another (such as pork), the simple truth is that dietary customs have less to do with rational thought, history, or science than they do with the social need to created tribal segregation.
We are the people that do not eat cow.
We are the people that do not eat pig.
We are the people that eat fish on Friday.
Fish on Friday? What?! Where did this strange custom come from? It is not in the Bible, in either the Old or New Testaments.
It seems this particular dietary restriction started as a "Friday Fast" which took the form of abstaining from animal meat on Fridays. This fast was supposedly to commemorate the crucifixion of Jesus Christ on Good Friday, but in practice it probably had more to do with controlling the congregation through arbitrary ritual.
It's worth noting that different nations and cultures have embraced a wide variety of "meatless" days, and for a wide variety of reasons, from economic to political, and from scarcity during war to health.
Somewhere along the line, "meatless Fridays" were relaxed to allow fish, but not beef, lamb, goat, rabbit, or chicken.
A rumor has it that "Fish on Friday" traditions were started as a secret papal pact with the Italian fishing industry designed to create a market for under-employed fishermen. That sounds right, but there is no solid support for the notion. It's "truthy," which is to say, it is not the truth.
One thing we do know is that religions are as plastic as Silly Putty, adding prohibitions and removing them with equal abandon, and without rhyme or meter.
And so, when Catholics came to the New World, and discovered millions of beaver in our streams and rivers, the "only eat fish on Fridays" dictum was questioned or even ignored.
In the 17th century, Francois de Laval, the first Bishop of Quebec, wrote to theologians at the Sorbonne and asked whether his flock might be permitted to eat beaver meat on Fridays during Lent, despite the fact that meat-eating was forbidden. Since the semi-aquatic rodent was a skilled swimmer, the Church declared that the beaver was a fish. Being a fish, beaver barbeques were permitted throughout Lent. Problem solved!
And what of the Capybara in equally Catholic South America? It too was declared a fish!
And what of American Alligator? In 2010, the Archbishop of New Orleans said "alligator is considered in the fish family" as it's cold blooded.
In 1962, McDonald's came out with the Filet-O-Fish sandwich so that Catholics would have something to eat in that establishment on Friday, but in 1966 the Catholic Church dropped the "Fish on Friday" rule with Vatican II. What about the Filet-O-Fish sandwich? It proved popular enough on its own, that it's still a staple of McDonald's to this day.