The Hebrew dietary laws, or laws of kashrut, were first set forth in the biblical books of Leviticus and Deuteronomy about 3,000 years ago. As such, they were among the earliest such restrictions ever promulgated, although they do have parallels in other ancient civilizations. By slowing the assimilation of the dispersed Jewish people into other cultures, the dietary laws helped to maintain the Jews’ uniqueness and thus facilitated their role in history.
Like other customs, dietary taboos and laws developed over time. It was their codification in the books of Leviticus and Deuteronomy in about 1000 b.c., their subsequent elaboration in the Talmud, and the central place of the Hebrew scriptures in the culture of the Jewish people that crystallized the dietary laws and preserved them over the millennia.
A central part of the dietary laws are the lists of permitted and taboo animals. These consist of general rules based on broad classifications. Among quadrupeds, only animals that both have a cloven hoof and chew their cud may be eaten. Examples of animals that fail this test are specifically mentioned in the Bible: the camel, rock-badger, hare, and pig. Food animal taboos are quite common among ancient peoples around the world, and may derive from a fear of absorbing the undesirable characteristics of a particular creature. Pigs, for example, were forbidden to many of the peoples of the Middle East (pork is proscribed for Muslims as well as for Jews, and comparable restrictions existed among the ancient Egyptians and Babylonians). They were also banned by the ancient Hindus, traditional Navajo, the native peoples of Guyana, the Lapps, and a tribe in Borneo.
For edible aquatic animals, the Hebrew law mandates both fins and scales, which eliminates all shellfish as well as eels, squid, and octopus. All insects are forbidden, with the exception of those that “have jointed legs above their feet, wherewith to leap upon the ground,” that is, locusts, crickets, and grasshoppers. Reptiles and amphibians, carnivorous and aquatic birds, bats, and animals with paws such as rodents and members of the weasel family are also banned.
In addition, laws apply to the conditions under which an animal may be eaten. Animals that died naturally, as well as carrion, are forbidden. Detailed procedures for slaughtering food animals require cutting the throat in a single slash with a razor-sharp knife. This ensures that death is immediate, thereby minimizing the animal’s pain. The laws also mandate that neither the blood nor the fat around the internal organs is consumed. Scholars believe that such laws derive from ancient notions that the vital essence or soul of an animal resided in these substances. Similarly, eating the sciatic nerve of the thigh, associated in Biblical times with the function of procreation, is banned.
Meat and milk may not be eaten, cooked or stored together, based on a Biblical proscription against boiling a kid goat in its mother’s milk. In fact the law may have been intended to be more specific than later interpretations held. It has been suggested that it was meant to ban a particular Canaanite fertility ritual known from a 3,400-year-old text, in which a kid was boiled in milk. The first five and most ancient books of the Hebrew Bible, called the Torah, repeatedly command the people to avoid such pagan rites and customs.