This is a book I read 4 or 5 years ago, back in high school. It was in a list of books our teacher gave us; we had to choose one and read it, and then write a paper about it.
When I saw the weird title I knew that would be the book I was going to read, and I'm sure it was a good choice because it really gave me some hours of good reading and kind of blowed my mind.
Have you ever wondered why indians worship cows? Or why muslims and jews are not allowed to eat meat? Well, the author, Marvin Harris, did. And he has this theory that there is a logical reason for people, society, to act that way. He states that every single human social behaviour (as weird or senseless as it can be) is ultimately caused by economic/survival needs or by environmental conditions like climate.
The book tells us that indians worship cows for the simple reason that they something to work/plow their lands with, fuel to keep them warm in winter, milk and flooring material, and a cow provides all that without the unnaffordable cost of buying tractors, gas/oil, etc. Cows are the tractors, fuel and heating. They don't eat beef because they need the cows for those other purposes. But people likes beef...the solution? Cows are sacred. You can't eat them. But yes, use them for whatever other needs you have and make them work so we keep the country running.
About the pig issue, it's pretty silly too. Islam and Judaism started in a desert-like place. Breeding pigs consumes a lot of water compared to other animals like sheeps or goats. For practical, economic purposes, eating pork was banned by those religions (by some smart guy that thought it was a bad idea to waste water in a desert landscape) At least it makes more sense than banning them for "being nasty" as those religions claim, when actually pigs are only that way if you breed them in a crowded, muddy farmyard. Pata Negra pigs prove that.
Concerning wars and witches, things get a bit more complicated. I encourage you to read the book and find out by yourselves! Or I may just re-read that part and write a review. We will see.