In 1519, when Hernando Cortez and his band of conquistadores first arrived at Tenochtitlán, the capital of the Aztec empire, they were stunned by the beauty of the metropolis they saw rising across the lake. A year and a half later, their awe had turned to horror as they watched 62 of their party ritually sacrificed at one of the many temple pyramids that dotted the city. Such occurences ended soon after, with Spanish conquest proper, but in their time the Aztecs practiced human sacrifice on a large scale. Why?
The good riverrun discusses the practice as a religious rite, and there is no doubt that human sacrifice had a deeply resonant religious significance. After all, the sacrifices happened at the top of the temples, and the freshly ripped-out hearts were placed on a special altar for the gods. Maybe the victims even went willingly, as he suggests, though I'd be a little more cautious about romanticizing such practices. But that's just me.
riverrun's story is fine as far as it goes, but it stops with the death. What happened to the bodies of the dead? In Tenochtitlán, at least, we have some idea, for the Europeans who witnessed such sacrifices, Cortez and his compatriats, wrote about what they observed.
The heads were severed and placed on racks in central plazas near the pyramids - I saw stone plynths at Chichén Itzá which were carved all around with skulls, a ghastly echo of the sight that so horrified the Spanish. If the victim was a prisoner of war, as many were, his limbs were the property of the warrior who had captured him on the field of battle. That warrior would later give a feast, serving up the limb meat stewed with tomatoes and peppers. The torso, meanwhile, went to feed the carnivore residents at the zoo.
Some archeological evidence supports these vivid and disturbing claims: unearthed piles of headless rib cages with no limb bones, human skulls stacked nearby.
So it seems likely that cannibalism was a part of Aztec human sacrifice.
But anthropologist Michael Harner has gone much further, arguing that cannibalism was the reason for Aztec human sacrifice. In a famous 1977 article published in Nature magazine, "The Enigma of Aztec Sacrifice", Harner claimed that cannibalism was necessary to the Aztecs because it provided them with essential amino acids and protein that they could not get from any other food sources. (The argument was later championed by Marvin Harris as part of his articulation of cultural materialism, the idea that a "scientific" view of culture must be built from a materialist base - culture as protein, critics charge.) In 1978 Bernard R. Ortiz de Montellano refuted Harner's argument in an equally famous article, "Aztec Cannibalism: An Ecological Necessity?", published in Science. Let's have a look at the arguments.
It is generally accepted in anthropology that civilization (the growth of settlements), agriculture, and population growth all arise together. Though anthropologists quibble about which is the cause and which the effect, all agree that higher population densities require domestication of plants and animals, which in turn require a settled population to tend them.
In the case of Mesoamerica, Harner argues, there were no appropriate herbivores extant for domestication, and thus as the population began to grow the native inhabitants focused on plant domestication - notably "The Three Sisters": beans, corn, and squash. Harner dismisses these as adequate food sources because they need to be consumed together to provide enough protein, but as Montellano points out, that is precisely how they are eaten in much of Latin America today. In addition, the processing of corn with lime to make masa harina, from which tortillas are made, greatly increases the calcium and niacin content of the diet.
Harner argues that instead of domesticating animals, existing wild game - deer, turkey, ducks and so on -was simply hunted to extinction. (Dogs were known, but are considered by Harner to be poor candidates for domestication because, as carnivores, they compete with humans for meat.) Though The Three Sisters provide sufficient protein when eaten together - and remain the staple for poor Latin Americans - Harner argues that meat is a better source of protein and much more prized around the globe, and thus that people will incorporate it into their diet in any way they can, including cannibalism. (It is true that though modern hunter-gatherers like the !Kung gain the bulk of their nutrients from gathered plants, they consider meat the more prestigious food source.)
Harner argues that frequent droughts caused crop failure, and that human flesh was an important food source to avert famine during such hard times. He neglects to mention an ingenious indigenous solution to drought: chinampas, raised beds dug out of the swampy lowlands. Crops flourished in the rich soil of the beds which, because they were surrounded by canals, were immune to drought. And the waterways provided food sources as well: plentiful scum which was dried and formed into notorious (to the Spanish) "scum cakes", as well as myriad small animals. (Small water-dwellers are a valuable food source in much of Asia too, and one reason why the abundant chemicals required for Green Revolution "supergrains" was so counterproductive: it killed off the fish and insects that grew amongst the paddy and on which people depended for protein. If only those biotech guys had consulted with an anthropologist first...but that's another story.)
Valuable food sources that flourished in the swampy environments of the chinampas included fish, frogs, water flies, water beetles, grasshoppers, and worms. Harner considers these insignificant as food sources, but as Montellano points out, that's just ethnocentric. In the poor northeastern areas of Thailand people survive off sticky rice garnished with fantastic spicy salads made from bugs; it's a treat I personally eschewed, but which were much prized by locals. What westerners won't eat is often daily fare for the poor in other parts of the world. The Mesoamericans also hunted armadillo, snakes, salamanders, and wild dogs. The numbers may have dwindled after centuries of hunting, but all these food sources were not eradicated. Wild meat there was.
Montellano and Harner agree that it was only the elite of Aztec society - the adult male warriors and the priests - who actually ate human flesh with any regularity. Harner believes that the goal of the (male) lower classes was to rise up into the elite through bravery in battle, and thus gain access to that much-needed protein. Montellano points out that childhood is the critical time to consume sufficient nutrients, and that if Aztec boys were actually severely protein deficient, they would never grow into men at all - yet grow into men they did. When they became men, if they were able to prove themselves in battle, many more rewards awaited them than an arm or a leg: they alone were permitted to drink chocolate and wear the elaborate sumptuary and ceremonial markers of their status. They enjoyed prestige, wealth, and placement in government office that commoners could only dream of.
Access to human flesh may have been one privilege of rank, Montellano argues, but it was not a particularly important source of protein. He asserts that Harner greatly overestimates the numbers of people actually sacrificed based on biased accounts of the Spanish conquistadores, who were intent on exaggerating their stories to give their king a reason to conquer Mexico. For example, Cortez claimed that the Aztecs were drunken sodomites - a common claim to justify colonization which says little about real practice. And even based on Harner's estimates of population and numbers of sacrificial victims, some quick but gruesome calculations by Montellano reveal that the amount of meat eaten be each warrior or priest would be negligible.
Montellano also points out that Harner completely neglects to mention the enormous importance of tribute to the Aztec economy. Each Aztec battle was effected to gain dominance over a neighbour who would then be obliged to provide tribute in the form of food to the Aztec empire. That tribute, much of which was levied in grains, was far more important to the survival of the Aztec empire than the meat of war captives.
So, why Aztec human sacrifice and cannibalism? Certainly, it resonated with the religious beliefs of the Aztecs, and it was practiced, albeit on a lesser scale, throughout the pre-conquest Americas. In the Aztec case, it could also have been a form of terror exercised on dominated neighbours: submit to us and give us tribute, or we'll fight you, kill your warriors, and you'll end up giving us tribute anyway. But an ecological necessity, as Harner claims? I don't think so.
Harner's article is currently available online at http://www.rose-hulman.edu/~delacova/aztecs/sacrifice.htm
Montellano's is currently available online at http://www.rose-hulman.edu/~delacova/aztecs/montellano.htm