Human sacrifice is known to have been an aspect of Aztec culture, although the extent of the practice is debated by scholars. The Spaniards who first met the Aztecs explicitly stated in their writings that human sacrifice was widely practiced in Mesoamerica. For example, Bernal Díaz's The Conquest of New Spain includes eye-witness accounts of the remains of sacrificial victims. In addition, there are a number of second-hand accounts of human sacrifices written by Spanish friars, told to them by native eye-witnesses.

Presently, scholars largely accept that human sacrifice was practiced throughout Mesoamerica, including the Aztec empire. Since the late 1970s, excavations of the offerings in the Great Pyramid of Tenochtitlan, Teotihuacán's Pyramid of the Moon and other archaeological sites have provided physical evidence of human sacrifice among the Mesoamerican peoples.[1][2][3]

A wide number of interpretations of the Aztec practice of human sacrifice have been proposed by modern scholars, both with regards to its religious and social significance. For example, one theory that has been widely discredited is that the Mesoamerican diet was lacking protein and that cannibalism of sacrificial victims was a necessary part of the Aztec diet.[4] Other theories link the practice to special socio-psychological factors or see it as a political tool. Most Mesoamerican scholars however see it as a part of the millennia-long cultural tradition of human sacrifice in Mesoamerica.

Human Sacrifice among pre-Columbian indigenous populations is a controversial topic today. The discussion of human sacrifice is also tied with the classic conflict between viewing indigenous peoples as either "noble savages" or "primitive barbarians" also within modern scholarship, where some scholars tend to romanticize the description of human sacrifice while others tend to exaggerate it.

The practice of human sacrifice was widespread in the Mesoamerican and in the South American cultures during the Inca Empire.[5][6] Like all other known pre-Columbian civilizations of Mesoamerica the Aztecs practiced human sacrifices. The extant sources describe how the Aztecs sacrificed human victims on each of their eighteen festivities, one festivity for each of their 20-day months.[7] It is unknown if the Aztecs engaged in human sacrifice before they reached the Anahuac valley and started absorbing other cultural influences. The first human sacrifice reported in the sources was the sacrifice and skinning of the daughter of the king Cóxcox of Culhuacán, this story is a part of the legend of the foundation of Tenochtitlan.[8] Several ethnohistorical sources state that under the guidance of Tlacaelel the importance of human sacrifice in Aztec history was given extra emphasis.

Sacrifice was a common theme in Mesoamerican cultures. In the Aztec "Legend of the Five Suns", all the gods sacrificed themselves so that mankind could live. Some years after the Spanish conquest of Mexico, a body of Franciscans confronted the remaining Aztec priesthood and demanded, under threat of death, that they desist from their murderous practice. The priests defended themselves by speaking out their Weltanschauung:

What the Aztec priests were referring to was a central Mesoamerican belief: that a great, on-going sacrifice sustains the universe. Everything is tonacayotl: the "spiritual flesh-hood" or "bodily [sacrificial] presence" of the gods on earth. Everything —earth, crops, moon, stars and people— springs from the severed or buried bodies, fingers, blood or the heads of the sacrificed gods. Humanity itself is macehuale, "the dead brought back to life through penance".[10] A strong sense of indebtedness was connected with this worldview. Indeed, nextlahualli (debt-payment) was a commonly used metaphor for human sacrifice, and, as Bernardino de Sahagún reported, it was said that the victim was someone who "gave her service".

Human sacrifice was in this sense the highest level of an entire panopoly of offerings through which the Aztecs sought to repay their debt to the gods. Both Sahagún and Toribio de Benavente (also called "Motolinía") observed that the Aztecs gladly parted with everything: burying, smashing, sinking, slaying vast quantities of quail, rabbits, dogs, feathers, flowers, insects, beans, grains, paper, rubber and treasures as sacrifices. Even the "stage" for human sacrifice, the massive temple-pyramids, was an offering mound: crammed with treasures, grains, soil and human and animal sacrifices that were buried as gifts to the deities. Adorned with the land's finest art, treasure and victims, these temples had become buried offerings under new structures every half a century.

The sacrifice of animals was common, a practice for which the Aztecs bred dogs, eagles, jaguars and deer. Objects also were sacrificed, broken and offered to their gods. The cult of Quetzalcóatl required the sacrifice of butterflies and hummingbirds.

Self-sacrifice was also quite common; people would offer maguey thorns, tainted with their own blood and, like the Maya kings, would offer blood from their tongue, ear lobes, or their penis.[11] Blood held a central place in Mesoamerican cultures. The Florentine Codex reports that in one of the creation myths Quetzalcóatl offered blood extracted from a wound in his own penis to give life to humanity. There are several other myths in which Nahua gods offer their blood to help humanity.[12]

Common people would offer maguey thorns with their blood.[13] Lloyd deMause has argued that, like present-day self harmers, the Aztecs also practiced bloodletting from cuts made with obsidian knives or bone needles on fleshy parts of the body, like earlobes, lips, tongue, chest and calves.[14] This was considered private and a personal act of penitence toward the gods. The thorns were put in a ball of straw called zacatapayoli and later placed in an adoratorium.
Maya Queen "Lady Xoc" draws a barbed rope through her pierced tongue in the Yaxchilan Lintel 24.
Maya Queen "Lady Xoc" draws a barbed rope through her pierced tongue in the Yaxchilan Lintel 24.

During social or environmental stress, the Maya kings would make a wound on their tongue or on their penis, and pass a piece of rope through it.[15] If this supreme sacrifice failed it was believed the entire dynasty could fall.

The cycle of fifty-two years was central to Mesoamerican cultures. The Nahua's religious beliefs were based on a great fear that the universe would collapse after each cycle if the gods were not strong enough. Every fifty-two years a special New Fire ceremony was performed.[16] All fires were extinguished and at midnight a sacrifice was made. The Aztecs waited for the dawn. If the Sun appeared it meant that the sacrifices for this cycle had been enough. A fire was ignited on the body of a victim, and this new fire was taken to every house, city and town. Rejoicing was general: a new cycle of fifty-two years was beginning, and the end of the world had been postponed, at least for another 52-year century. (A similar ceremony is still practiced by small indigenous groups, but without human sacrifice.) The ceremony was older than the Aztecs. While originally it was believed it was a matter of luck to survive, the Aztecs thought that constant sacrifice through the fifty-two year cycle could postpone the end.

According to Miguel León-Portilla, Tlacaelel reformed the original Nahua religion and the Aztecs viewed themselves as the main representatives for feeding the gods. This gave them a new sense of identity, from "people without face" as they were called by hostile neighbors, to the people in charge of the existence of the universe. Thus they began to call themselves "The people of the sun". Other researchers dispute León-Portilla's perspective, pointing to the relative lack of primary sources.

Huitzilopochtli was the tribal deity of the Mexica and, as such, he represented the character of the Mexica people and was often identified with the sun at the zenith, and with warfare.

When the Aztecs sacrificed people to Huitzilopochtli the victim would be placed on a sacrificial stone.[17] Then the priest would cut through the abdomen with an obsidian or flint dagger.[18] The heart would be torn out and held towards the sky in honor to the Sun-God; the body would be carried away and either cremated or given to the warrior responsible for the capture of the victim. He would either cut the body in pieces and send them to important people as an offering, or use the pieces for ritual cannibalism. The warrior would thus ascend one step in the hierarchy of the Aztec social classes, a system that rewarded successful warriors.

Tezcatlipoca was generally considered the most powerful god, the god of night, sorcery and destiny (the name tezcatlipoca means "smoky mirror", or "obsidian"). The Aztecs believed that Tezcatlipoca created war to provide food and drink to the gods. Tezcatlipoca was known by several epithets including "the Enemy" and "the Enemy of Both Sides", which stress his affinity for discord. Tezcatlipoca had the power to forgive sins and to relieve disease, or to release a man from the fate assigned to him by his date of birth; however, nothing in Tezcatlipoca's nature compelled him to do so. He was capricious and often brought about reversals of fortune. To the Aztecs, he was an all-knowing, all-seeing nearly all-powerful god. One of his names can be translated as "We Who Are His Slaves".

Some captives were sacrificed to Tezcatlipoca in ritual gladiatorial combat. The victim was tethered in place and given a mock weapon. He died fighting against up to four fully armed jaguar knights and eagle warriors.

A curious sacrifice was that of a young handsome Nahua. Throughout a year he would be dressed in Tezcatlipoca's likeness and treated as a living incarnation of the God. At the end of the year at the festival of Toxcatl he would climb up the temple's steps voluntarily and offer himself for sacrifice. This was accomplished by recruiting a young volunteer and letting him live a luxurious life for the year. The youth would represent Tezcatlipoca on earth; he would get four beautiful women as his companions until he met his destiny, in the meantime he walked through the streets of Tenochtitlan playing a flute. On the day of the sacrifice a feast would be held in Tezcatlipoca's honor. The young man would climb the pyramid, break his flute and surrender his body to the priests. This was one of the more solemn festivities for the Aztecs. Sahagún compared it to the Christian Easter.

To appease Huehueteotl, the fire god and a senior deity, the Aztecs had a ceremony where they prepared a large feast at the end of which they would burn captives alive. Motolinía and Sahagún reported that the Aztecs believed that if they did not placate Huehueteotl a plague of fire would strike their village. Huehueteotl was believed to have a preference for the bodies of newlywed couples. The sacrifice was considered a double offering to the deity. Just before the victims died in the flames they were removed from the fires to have their the hearts extracted.

Tláloc was the god of rain. The Aztecs believed that if sacrifices weren't supplied for Tláloc, rain wouldn't come and their crops wouldn't flourish. Leprosy and rheumatism, diseases caused by Tláloc, would infest the village. Tláloc required the tears of the young as part of the sacrifice. The priests made the children cry during their way to immolation: a good omen that Tláloc would wet the earth in the raining season.

It has often been claimed by scholars that, the Aztecs resorted to a form of ritual warfare, the Flower War, in order to obtain living human bodies for the sacrifices in time of peace. This claim however has been severely criticised by scholars such as Ross Hassig[22][23]and Nigel Davies[24] who claim that the main purpose of the Flower Wars was political and not religious and that the number of sacrificial victims obtained through flower wars was insignificant compared to the number of victims obtained through normal political warfare.

According to Diego Durán's History of the Indies of New Spain, and a few other sources that are also based on the Crónica X, the Flower Wars were originally a treaty between the cities of Aztec Triple Alliance and Tlaxcala and Huexotzingo motivated by a famine in Mesoamerica in 1450. Aztec prisoners were also sacrificed in Tlaxcala and Huexotzingo. The capture of prisoners for sacrifices was called nextlaualli ("debt payment to the gods"). These sources however are contradicted by other sources, such as the Codex Chimalpahin, which mentions "Flower Wars" much earlier than the famine of 1450 and against other opponents than the ones mentioned in the treaty.

Because the objective of Aztec warfare was to capture victims alive for human sacrifice, battle tactics were designed primarily to injure the enemy rather than kill him. After towns were conquered their inhabitants were no longer candidates for human sacrifice, only liable to regular tribute.

Slaves also could be used for human sacrifice, but only if the slave was considered lazy and had been resold three times.

Most of the sacrificial rituals took more than two persons to perform. In the usual procedure of sacrifice, the victim would be taken to the top of the temple.[26] Then the victim would be laid on a stone slab by four priests, and his abdomen sliced open by a fifth priest with a ceremonial knife made of flint. The cut was made in the abdomen and went through the diaphragm. The priest would grab the heart and tear it out, still beating. It would be placed in a bowl held by a statue of the honored god, and the body thrown on the temple's stairs.[27]

The body parts would then be disposed off: the viscera fed the animals in the zoo; the blooding head was placed on display in the tzompantli, which means hairy skulls.[28] Not all the skulls in the tzompantlis were victims of sacrifice. In the Anales de Tlatelolco it is described that during the siege of Tlatelolco by the Spaniards, the Tlatelolcas built three tzompantli: two for their own dead and one for the fallen conquerors, including two severed heads of horses.

Other kinds of human sacrifice, which paid tribute to various deities, approached the victims differently. The victim could be shot with arrows (in which the draining blood represented the cool rains of spring); died in unequal fighting (gladiatorial sacrifice) or in the bloody Mesoamerican game known as ulama; burned (to honor the fire god); flayed after being sacrificed (to honor Xipe Totec, "Our Lord The Flayed One"), or drowned.

For the re-consecration of Great Pyramid of Tenochtitlan in 1487, the Aztecs reported that they sacrificed about 80,400 prisoners over the course of four days, though they were probably much less. (According to Ross Hassing, author of Aztec Warfare, "between 10,000 and 80,400 persons" were sacrificed in the ceremony.[30]) Four tables were arranged at the top so that the victims could be jettisoned down the sides of the temple. Michael Harner, in his 1997 article The Enigma of Aztec Sacrifice, estimates the number of persons sacrificed in central Mexico in the 15th century as high as to 250,000 per year. Fernando de Alva Cortés Ixtlilxochitl, a Mexica descendant and the author of Codex Ixtlilxochitl, claimed that one in five children of the Mexica subjects was killed annually. Victor Davis Hanson argues that an estimate by Carlos Zumárraga of 20,000 per annum is more plausible. Other scholars believe that, since the Aztecs always tried to intimidate their enemies, it is more likely that they could have inflated the number as a propaganda tool.[31] The real number of sacrificed victims during the 1487 consecration in unknown.

The same can be said for Bernal Díaz's inflated calculations when, in a state of visual shock, he grossly miscalculated the number of skulls at one of the seven Tenochtitlan tzompantlis. According the Florentine Codex, fifty years before the conquest the Aztecs burnt the skulls of the former tzompantli. Mexican archeologist Eduardo Matos Moctezuma has unearthed and studied some tzompantlis.