There is a fascinating conversation going on around the internet ( in response to Shmarya Rosenberg's article at Tablet magazine where she speculates on the source of the prohibition of pork in Jewish food laws.
In one sense the answer is ultimately that God said so in Leviticus 11 where the Israelites are instructed not to eat certain animals:
"The LORD said to Moses and Aaron, “Say to the Israelites: ‘Of all the animals that live on land, these are the ones you may eat: You may eat any animal that has a divided hoof and that chews the cud. There are some that only chew the cud or only have a divided hoof, but you must not eat them...the pig, though it has a divided hoof, does not chew the cud; it is unclean for you. You must not eat their meat or touch their carcasses; they are unclean for you."
Despite the simplicity of this answer to the question, there is all kinds of speculation about how these laws may have emerged in the history of the people. This is true for kosher food laws and all the other religious food laws we're learning about this year.
The common speculation I've heard regarding pork is that through experiences with trichinosis people came to see the meat as unsafe to eat so when it came time to lay down the law, those laws formalized the hard-earned folk wisdom of the people.
Rosenberg points out that the prohibition against pork is one among many prohibitions against meat but it stands alone as the definitive Jewish food law. She points out that despite the Jewish law against eating shellfish:
Archaeological digs in Israel have uncovered ancient biblical-era Israelite settlements where remains of shellfish are plentiful, but pig bones were not found. And even today there are many Jews like my friend’s family who eat shrimp and crab without a trace of guilt but would never eat pork. What could be so bad about pigs?
Rosenberg takes her cure from Christopher Hitchens to explain the exemplary power of the pork prohibition:
In God is not Great, Hitchens notes uneasy similarities between humans and pigs: Porcine DNA and human DNA are very similar, so much so that porcine heart valves can be transplanted into humans; pigs are noticeably smarter than other farm animals; and pig skin looks almost human, so much so that the smell and look of suckling pig and roasting human infants is, according to those who have had the misfortune of smelling and seeing both, disconcertingly similar. And make no mistake about it—many ancient Israelites had that misfortune. Hitchens thought this was the basis for the Jewish taboo against eating pork...
She puts it in the context of animal and child sacrifice that was common in that time and speculates that it was a way to steer people clear of the common practice of child sacrifice in the ancient world. She suspects that sacrificing and eating pigs was a slippery slope to child sacrifice.
Hitchens dismissed Judaism’s anti-pork taboo as a Bronze Age superstition. But was it? Or was the Torah—divine, divinely inspired, or simply man-made—trying to do whatever it could to wean humans away from the perceived need to murder their own children?
Go here for a fascinating rundown of other possibilities at Andrew Sullivan's Dish.
image from cdn.greenprophet.com