Is there a “rational” explanation for human sacrifice? Of course there is; indeed, there are several, depending on which premises are used to construct the culturally relative concept of what counts as “rational.” Anthropologists have put forward several competing explanations for human sacrifice. These are not mutually exclusive. There is no good reason to think any one is definitive or that a mono-causal explanation suffices for a particular case. Competing explanations are usually complementary.
None of this is really news. Most anthropology undergraduates know these things. It is therefore amusing to learn that economists have “discovered” that human sacrifice can be rational. Brian Leesing, a rational-choice theorist at George Mason University, explains:
There is a rational choice and explanation for all forms of human sacrifice. Typically people think of something like the Aztec model. The Aztecs weren’t buying people and throwing them off the sides of pyramids. What they were doing, might make a lot more sense to people today: they were sacrificing prisoners of war, so defeated other guys and criminals. It’s not that hard to imagine why it is, in a society where warfare is endemic, why you’d want to have capital punishment for your enemies and where you’re trying to control crime why you’d capitally punish criminals.
This is one explanation. It may have made “rational” economic sense for the Aztecs to kill captives rather than curate them. There is also a “religious” explanation:
The blood rituals were considered part of a reciprocal relationship between humankind and god; the ultimate gift is blood and is amongst the highest honour one can pay to the gods. Aztec blood rituals were an act of reciprocity for the blood the gods sacrificed of themselves in order to create the sun and the cosmos. Blood sacrifices ensured the gods would remain helpful and they ensured the sun would continue to shine, the fields would grow abundant crops and the wheels of life would continue to turn. Fear of pain and suffering inflicted by the gods in retribution for any lack of blood sacrifice would have been an overwhelming incentive to constantly sacrifice and appease the vengeful gods.
This is an emic explanation that is too idealist for me. There is also a ritual-cohesion (i.e., Durkheimian) explanation that I find more persuasive:
Aztec rituals, as powerful intensifiers of emotion, were singularly effective at producing experiences of the sacred; it makes better sense to say that rituals were for the sake of these emotional experiences than to say that they were for the sake of certain material outcomes (like victory in war, or a good harvest, or the avoidance of natural disasters), though they were obviously rationalized in such ways (e.g., as means to ensure that the sun rose every day, or to prevent the destruction of the world, etc.). At the end of the day, human sacrifice is, instrumentally speaking, pure waste: it only makes sense from the point of view of the intensified emotions (“experiences of the sacred”) that it helps produce in ritual context. In turn these emotions bound together the community and made for a particularly intense kind of social life.
There is also an ecological explanation. This one is particularly tasty:
With an understanding of the importance of cannibalism in Aztec culture, and of the ecological reasons for its existence, some of the Aztecs’ more distinctive institutions begin to make anthropological sense. For example, the old question of whether the Aztecs’ political structure was or was not an “empire” can be reexamined. One part of this problem is that the Aztecs frequently withdrew from conquered territory without establishing administrative centers or garrisons. This “failure” to consolidate conquest in the Old World fashion puzzled Cortés, who asked Moctezuma to explain why he allowed the surrounded Tlaxcalans to maintain their independence. Moctezuma reportedly replied that his people could thus obtain captives for sacrifice. Since the Aztecs did not normally eat people of their own polity, which would have been socially and politically disruptive, they needed nearby “enemy” populations on whom they could prey for captives. This behavior makes sense in terms of Aztec cannibalism: from the Aztec point of view, the Tlaxcalan state was preserved as a stockyard. The Aztecs were unique among the world’s states in having a cannibal empire. Understandably, they did not conform to Old World concepts of empire, based on economies with domesticated herbivores providing meat or milk.
It is undoubtedly the case that all four of these explanations work together to explain ritual human sacrifice in the Aztec Empire. All these explanations are “rational.”
This observation may, in turn, explain why rational-choice models (such as those favored by the Fed) have such a dim reputation among social scientists, historians, psychologists, behavioral economists, moral economists, and political economists. Rational-choice models can be manipulated to explain just about anything, almost always after the fact. They are not very good at predicting the future or for policymaking.