Via Tyler Cowen, Peter T Leeson has an interesting article on the economics of human sacrifice. He links human sacrifice to property rights and rational choice theory, but the fundamental idea doesn't depend on these right-wing shibboleths for its validity, IMHO.
It's one of the many disreputable bits of human history, but it seems to be a fact that human sacrifice has been pretty widely practiced at certain stages of human history. Why? Economists have their own fish to fry, but to me a good explanation needs to explain some selective advantage to the practice. Leeson's theory does that.
Besides the libertarian mumbo-jumbo, Leeson cloaks his model in a sort of Rube Goldberg mathematics - some funky algebra where a straight forward minimization would be more to the point - but the key points don't depend on either of those.
His model subjects are the Konds of Orissa India, who practiced a truly gruesome form of human sacrifice in historically recent times. These people lived in a loosely organized hierarchy at the smaller scale but consisted of highly competitive and mutually warring communities at the largest scale. As farmers, they were subject to the vicissitudes of nature as well as predation by their neighbors. In this situation, Leeson argues, the wealthiest communities were the biggest target for predators and hence the most vulnerable. For them, Leeson argues, ritual destruction of wealth was a way of making themselves less vulnerable to attack and hence adaptive.
You should read the paper to see the details of the logic, but the principle is illustrated by another practice of the same people: tattooing their women. According to their own accounts, they did this not because they thought that made them more attractive, but the opposite. It seems that a neighboring power liked to seize their women, so tattooing them uglified them enough to make them unlikely targets.
The British, on discovering their ritual immolations, tried a lot of things to suppress them: violence, bribes, and so on. But when they asked the Kond what they would take to stop the sacrifices which were ostensibly to appease their blood-thirsty gods, they asked for law and order. So the British stopped the inter-community violence and the human sacrifices stopped.