Mexico City’s “tower of skulls” could tell us about pre-Columbian life
Last month, archaeologists in Mexico City unearthed the eastern façade of a tower of skulls near the 700-year-old site of the Templo Mayor, the main temple in the former Aztec capital city of Tenochtitlan. It’s a morbidly sensational find, but it’s also a potential treasure trove of information about the people who died at Tenochtitlan in the city’s final centuries. Here’s what the skulls in the tower could tell us if we ask them—and why we’d have to ask very carefully.
Archaeologists found 119 skulls built into the structure, a morbid addition to the 484 skulls found on the northeast side of the tower, which archaeologists rediscovered in 2015. Since 2015, excavations have reached 3.5 meters below modern street level, into the layers of ground once trod by Aztec priests, onlookers, and sacrificial victims. From those excavations, we now know that the 4.7 meter (15.4ft) tall tower was built in at least three phases, starting in the 15th century.
The nearby Templo Mayor once housed important shrines to the war-god Huitzilopochtli and the rain and farming god Tlaloc. Many of the victims sacrificed to the two gods probably ended up as building blocks for the tower, properly known as the Huei Tzompantli, nearby. A tzompantli is a wooden scaffold for displaying skulls (exactly as the name suggests if you happen to speak Nahuatl; the word means something along the lines of “skull rack” or “wall of skulls”). The temple district of Tenochtitlan once boasted at least seven of them.
Spanish conquistadors destroyed nearly every tzompantli they found when they swept through Aztec lands in the 1500s; elsewhere in Mexico City, archaeologists have found the scattered fragments of some of those destroyed walls of skulls. So far, the Huei Tzompantli is the only one found mostly intact in the city. The conquistadors destroyed the most recent phase of its construction when they razed the Templo Mayor, but older parts of the tower remained.
War, debt, and human sacrifice
At first glance, literal walls of human skulls evoke only horror and a deep sadness for the victims. Eventually, though, it’s hard not to think like an anthropologist (mileage may vary, of course). Hundreds of skulls represent the remains of centuries of human cruelty, but they also represent an unusually large glimpse into the people who lived in Central America in the centuries before European colonization, which archaeologists call the Postclassic period.
Even without removing any of the skulls from the wall, it’s easy to tell that many of the people who died at the Templo Mayor had once used boards to modify the shapes of their heads. Some had their heads pressed against cradleboards to flatten their skulls when they were children. Others had tied boards across their foreheads and the backs of their skulls to produce a different shape. That offers some insight into the cultures from which the victims came.
So far, archaeologists at the site say that about 75 percent of the skulls probably belonged to adult men, while the rest probably belonged to women—except for three, whose teeth clearly marked them as young children. Those demographics make sense, since Aztec texts and artwork tell us that sacrificial victims were often captives taken during wars with neighboring states.
For ancient Mesoamericans, warfare was sometimes a kind of ritual written large. Certain conflicts called flower wars were tightly bound by conventions and rules. And some archaeologists speculate at least some of the captives—men, women, and at least three children—ended up as human sacrifices to help the ruling elites of Tenochtitlan pay their debts to the gods and keep the world habitable.
“Although we cannot determine how many of these individuals were warriors, perhaps some were captives destined for sacrificial ceremonies. We do know that they were all consecrated, that is, they were turned into gifts for the gods or even personifications of the deities themselves, for which they were dressed and treated as such,” said archaeologist Barrera Rodríguez in a press release.
According to the Aztec worldview, the world ran on a contract between the gods and the rulers at Tenochtitlan. The gods caused water to flow and crops to grow, but in return, the rulers had to ensure that the gods had enough to eat and drink—and gods like Huitzilopochtli, Tlaloc, and Xipe Totec were literally bloodthirsty. They needed human blood in order to live and do their jobs. To the Aztec, this concept was known as nextlahualtin, or payment of debts.
All fall down
At the moment, we know a lot more about how the nextlahualtin victims probably died than we do about how they lived. Spanish colonizers described sacrificial rituals in alarming but informative detail in their accounts, and Aztec artwork and inscriptions also fill in some information. That’s how we know, for instance, that the skulls of the Huei Tzompantli probably had their flesh removed before being added to the wall.
The victims’ bare skulls could tell us a lot about their lives, however. Ancient DNA sequences could reveal something about who the victims were and how they’re related to modern Mesoamerican people. Radiocarbon testing could tell us when they died and maybe help put together a chronology of large rituals at Templo Mayor, or at least the construction of the tzompantli.
Stable isotopes of the element strontium in tooth enamel could help narrow down where these people came from. Bedrock in most places has a geochemical fingerprint: a nearly unique ratio of the isotopes strontium-86 and strontium-87. Plants take up strontium through their roots, so the strontium isotope ratio in a person’s bones will match the bedrock where most of their food grew. Teeth generally store strontium ratios from the first few years of life, while bone stores strontium from the last decade or so. It’s amazing to consider how much these individuals’ skulls could tell us about how people moved around in the Aztec world.
Measuring isotopes of carbon, nitrogen, and oxygen can also offer clues about where people lived and what they ate. Carbon-12 and carbon-13 ratios can offer clues about the kinds of plants someone ate; nitrogen can suggest how much meat or seafood made up a person’s diet; and oxygen isotope ratios can point to where people got their water and how dry the local climate was.
The only way to get any of that information, however, involves destroying a tiny bit of tooth or bone from each skull you want to study. And deciding when it’s appropriate to do that is complicated. It’s important to remember—as neither the Aztecs nor the Conquistadors potentially did—that the skulls in the walls of the Huei Tzompantli were once real people.
Most of the time, archaeologists and anthropologists who want to study indigenous remains need to work closely with members of indigenous groups related to the deceased, or at least ones who live on the land now. Making a case for destructive sampling requires clearing a very high bar for research questions even under normal circumstances, and these aren’t normal circumstances. There’s a wall of skulls involved, after all. Nothing about this was going to be normal.
“Although these individuals are an important sample of the population of the Postclassic period, each one of these skulls forms an architectural element that is part of the building and its symbolic discourse,” explained archaeologist Lorena Vasquez Vallin in a press release. In other words, destructive sampling of the Huei Tzompantli skulls (or even removing them for a closer look or a 3D scan) could bring down the house—literally.
https://arstechnica.com/?p=1734084