Meat for dinner?

The question has arisen again about whether we should allow farmed animals to be killed for food without pre-stunning them.  The procedure is called "halal" for Muslims and "kosher" for Jews.  Both words mean "proper" or "allowable" and both methods call for the animal to be killed while still "fully alive", and thus for strict adherents pre-stunning is not allowed. And the meat of the pig is taboo for both Muslims and Jews. But where do these ideas come from and why?  Problem is that for both peoples the stricture comes from their respective holy books and is thus inviolable. But why?  And it seems to me that it almost certainly all started out not as a matter of religion at all, but of public health. Both Muslims and Jews have traditionally lived in the Middle East where the weather is hot, and in such a climate in pre-refrigeration days, you had to be careful when eating meat, which could "go off" quickly and make you ill, if not kill you.  Pork is notorious for this (I remember as a kid and before we had we a 'fridge, we didn't eat pork unless there was an "r" in the month - i.e. not in the summer months).  So in those hot climates, pork was a no-no.  And for other meat it was essential that it was freshly killed and free from disease, and so to ensure this, the killing became a ritual. Whether there is any place for the idea in today's world of refrigeration and strict health controls is the question, but I think the concept is too deeply ingrained in the two religions for any possibility of change.  As has been mentioned before, there are those of both faiths who are prepared to use pre-stunning on the basis that alive does not necessarily mean conscious - after all you are alive when you are asleep - and maybe this is a way of satisfying both camps.