Almost 60 years ago, archaeologists discovered a cache of human bones in an underground cistern in Chichén Itzá, one of the most powerful cities of the ancient Maya. The cistern was connected to a cave located only a couple hundred feet from the Sacred Cenote, a water-filled sinkhole filled with the remains of hundreds of human sacrifices.

  When the discovery in the cistern, or chultún, was made on Mexico’s Yucatán Peninsula in 1967, archaeologists determined that young adults and children had been deposited there over a span of eight centuries and assumed that most of them were and young women; at the time, it was thought that the Maya preferred female victims for their ritual sacrifices.

But now a new DNA study has turned that assumption on its head, by revealing that all of the 64 sets of human remains sampled from the cave are from male victims, many of them brothers and cousins between the ages of three and six years old—and an unlikely number of identical twins.

“We were not expecting this to be the case,” says archaeogeneticist Roderigo Barquera of the Max Planck Institute for Evolutionary Anthropology in Germany and the lead author of a new study describing the analysis just published in the journal Nature.

“Traditionally, these kinds of burials are associated in Mesoamerican archaeology with fertility offerings, and fertility offerings usually feature females only.”

Mass burial

  In recent years, Barquera and his co-authors have taken another look at the bones recovered from the chultún and cave in 1967, which are now stored nearby.

Their new analysis suggests that the location was used for more than 100 burials between A.D. 500 and the 1300s.

  Most of the people buried there were interred before the 900s—roughly when Chichén Itzá was the dominant city of the northern Maya lowlands, which covered what are now Mexico’s Yucatán Peninsula, northern Guatemala, and Belize.

Earlier anthropological studies had revealed that the victims were mostly toddlers and young children; but this is the first time that their DNA has been analyzed, Barquera says.

As well as learning that only boys had been buried in the cave, the researchers were surprised to find that many had been closely related: At least a quarter were a brother or cousin to another boy buried in the same cave, and the burials included two pairs of identical twins.  

Identical twins occur only in about 0.4 percent of births, so finding two pairs of such twins among 64 burials is much higher than would be expected by chance, Barquera notes.

Hero twins

It’s not clear how widespread human sacrifice was among the Maya, although there are many Spanish reports of practice after they arrived in the Maya territories in the early 16th century.

It now seems the Maya mainly practiced human sacrifice in the later stages of their civilization, to seek favor from their gods for the fertility of their crops, or for rain, or for victory in war.

Twins feature prominently in Mesoamerican mythology and are a central theme in the Popul Vuh, a sacred narrative of the Kʼicheʼ Maya people thought to date from the earliest stages of Maya civilization.

According to the Popul Vuh, twins named Hun-Hunahpú and Vucub-Hanahpú descended into the underworld to play a ball game, but were sacrificed by the gods after they were defeated.

Despite his death, the head of one of the twins impregnated a maiden with the “Hero twins” Hunahpú and Xbalanqué, who went on to avenge their father through repeated cycles of sacrifice and resurrection.

Barquera notes that subterranean structures, such as the cave where the children were buried, were seen as entrances to the underworld; and it could be that the sacrifices of boy twins and close relatives—perhaps when true twins were not available—were part of rituals involving the Hero twins that were intended to ensure bountiful harvests of maize.

New questions for old bones

The new Nature study raises additional questions for archaeologists to answer. The first is the causes of death, since there are no visible human-made marks on the bones from the cave, unlike remains from the nearby Sacred Cenote.

“We couldn’t find any cut marks or any lesions that would point to specific methods of sacrifice,” Barquera says. “This indicates that the sacrifice did not involve, for example, heart extraction or decapitation—so maybe it was a different kind of sacrificial method.”

Further ancient DNA analysis could establish whether any of the children buried in the cave were from multiple generations of the same family, which may indicate that the honor—or curse—of providing sacrificial victims may have been an inherited privilege among certain families, Barquera says.

Disease immunity

The new analysis also involved analyzing blood samples from modern Maya who live near Chichén Itzá today; the results show a “genetic continuity” between the children buried in the cave and the modern people of the region.

Barquera says this indicates that the sacrificial victims came from the local population and not more distant communities across the Maya empire.

The researchers also saw distinctive differences between ancient and modern DNA sequences involving immunities to diseases, suggesting that the local Maya have adapted to certain infectious diseases, such as Salmonella enterica, introduced during the Spanish Colonial period, Barquera says.

Archaeologist and National Geographic explorer Guillermo de Anda, a researcher with Mexico’s National Institution of Archaeology and History, wasn’t involved in the latest study but has spent decades researching human sacrifices at Chichén Itzá, including numerous dives into the Sacred Cenote.

He recently went looking in the nearby jungle for the cave where the mass burial was discovered in 1967, but it seems to have been covered by what’s left of an airstrip built a few years later—but then abandoned—near the vast city ruins.

  “We would really love it to be there, but it looks like it’s gone forever,” de Anda says.

De Anda says that the proximity of the cave to the Sacred Cenote raises questions about why two different places so close to each other were both used to dispose of sacrificial victims; and the lack of visible causes of death on the bones from the cave burials is also a mystery that needs to be addressed.

This seems to be the first time that ancient DNA analysis has been used on any remains from Chichén Itzá, and De Anda hopes such techniques will now be used on the bones of sacrificial victims from the Sacred Cenote.

“This is a new thing for Chichén Itzá,” he says. “We are looking forward to doing it.”