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Religious food taboos are hard to explain. Hindus avoid beef but eat pork. Jews, Moslems, and Seventh Day Adventists eat beef but avoid pork.
It is hard to come up with a satisfactory practical explanation of such conflicting practices, although anthropologists have tried.
Practical explanations
One leading scientific explanations for the Hebraic pork taboo is that pigs make unsuitable domestic animals because they eat everything and therefore compete with their owners for food. This would be an issue in the periodically hot and dry lands of the Middle East where food can be scarce. Contrary to the theory the taboo persists when Moslems and Jews migrate to more productive ecologies.
The second main theory is that pigs are carriers of trichinosis, a serious parasitic illness. This theory is not too credible either. One issue is that the parasite is destroyed by thorough cooking. A practical answer would thus be to cook the pork thoroughly rather than avoiding it. Once again, the food taboo persists even when Hebraic peoples migrate to regions where trichinosis is not a problem.
Religious texts are of little help here either. We are told that pigs are unclean because they have cloven hooves, for example, but that is a circular argument. We are not told why one hoof shape is more unsanitary than another.
Such food taboos are intriguing because they are potentially very costly. After all, keeping the taboo can mean the difference between starving and being well fed. According to a relatively new theory of religion, costly food taboos are maintained by their social advantages rather than any practical benefit.
A social explanation
According to the costly signaling theory of religion, people are willing to take on significant ritual costs, such as prayer and fasting because these practices tie co-religionists together. By paying the ritual costs, a member of some religion expresses their commitment to the congregation.
Perhaps food taboos are simply another example of a costly ritual. In other words, by identifying with the religion, a member undertakes not only to observe the religious rituals but also to refrain from eating proscribed foods.
The notion that food taboos keep co-religionists together has much going for it. Indeed, it can be rather difficult for people from different religions to share a meal if they are so strict that they fear being contaminated when the unclean food touches their own.
According to this social explanation, it does not really matter what food is proscribed. The important point is that if you are a Hindu you agree to avoid beef without qualification as a sign of your commitment to the belief system. Similarly, Jews agree to avoid pork as one of their taboo species.
Not all food taboos are explicitly religious, of course. In the West, dogs are treated like family members so that any sort of cruelty to them is criminalized. The fact that farmers sometimes resorted to killing and eating the family dog during the Great Depression illustrates how desperate they were for food. In China, India, and other countries, dogs are commonly eaten, however, and restaurants specialize in the preparation of dog meat.
The bottom line, then is that some animals are tabooed, or eaten, purely because human groups make arbitrary agreements in these matters. If a person wants to fit in, they must follow the taboo. If they do not, they will be seen as different.
