Genetic analysis of the skeletons of 64 infant boys who are thought to have been sacrificed in the ancient Maya city of Chichén Itzá more than a thousand years ago may shed light on the symbolic role twins played in the myths and rituals of their civilisation.
In 1967, the remains of more than 100 children were found in a repurposed chultún, or underground cistern, near the sacred sinkhole at the ceremonial centre of the pre-Columbian city, which was one of the largest and most influential Maya settlements between AD600 and 1000.
A study of 64 of the children has established that most of them were buried in the chultún on Mexico’s Yucatán peninsula between AD500 and 900. DNA testing showed that all the analysed individuals were male, and that several were closely related, including two pairs of monozygotic twins. Most were estimated to be between three and six years old.
The location of the chultún – which is connected to a small underground cave – has led experts to speculate that it was the burial place for children who were sacrificed to support maize-growing cycles, or given as offerings to Chaac, the Maya rain god.
Twins feature prominently in Maya mythology and twin sacrifice is a central theme in the Popol Vuh, the sacred book of the indigenous Kʼicheʼ, one of the Maya peoples.
“In the Popol Vuh, the twins Hun Hunahpu and Vucub Hunahpu descend into the underworld and are sacrificed by the gods following defeat in a ballgame,” the researchers write in Nature.
“The head of Hun Hunahpu is then hung in a calabash tree, where it impregnates a maiden who gives birth to a second set of twins, Hunahpu and Xbalanque. These twins, known as the Hero Twins, then go on to avenge their father and uncle by undergoing repeated cycles of sacrifice and resurrection to outwit the gods of the underworld.”
Given that subterranean structures were seen as entrances to the underworld, the researchers add, “the twin and relative sacrifices within the chultún at Chichén Itzá may recall rituals involving the Hero Twins”.
The study’s lead author, Rodrigo Barquera, of the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Germany, said that while ritual sacrifice was a common practice among ancient Mesoamerican populations, the biological relationships between sacrificial victims had not been described before.
“We think that the people from Chichén Itzá were trying to symbolically replicate the Maya mythological stories and the representation of the twin heroes in this ritual burial,” he said. “For Maya, and Mesoamerican cultures in general, death is the ultimate offering and, as such, sacrifices bear high importance to their beliefs system.”
The study also contradicts an idea popularised in the 20th century that the ancient Maya preferred female sacrifices.
The researchers extracted DNA from the petrous portion of the temporal bone, which houses the inner ear and has proved optimal in preserving ancient DNA.
“We sampled only the left portion because that would make sure we sampled every individual only once,” said MPI-EVA archaeogeneticist and study co-author Kathrin Nägele.
“From the genetic similarities of two individuals, we can calculate the degree of genetic relationship. In this case, we found two pairs who were so similar they could only be identical twins, and at least three more who were full siblings. They could have also been twins, but fraternal twins, coming from two different egg cells,” she said.
“This is the first time we are able to confidently identify identical twins in the archaeological record.”
The researchers compared the genomes of the boys with those of present-day Maya communities, including 68 people from the village of Tixcacaltuyub, near Chichén Itzá’s ruins. They identified genetic traits in modern Maya that are likely to have arisen from the immune system adaptations their ancestors developed during the Spanish colonisation.
Despite their findings, however, the researchers have not been able to establish precisely how the 64 boys died.
“There are no cut marks or evidence of trauma, which tells us how they did not die,” said Barquera. “But we have not found a cause of death for them yet.”
Sacrifice remains the most likely explanation.
“At that time, children who died of diseases usually died within the first two years of life,” Barquera told El País. “It is rare to find so many dead aged between three and six years old. Also, if it were a burial, we would see a mix of sexes, but here there is a clear pre-selection of males. Many of them were related. And we also found two sets of twins. The possibility of it being a product of chance is practically zero.”
Christina Warinner, a Harvard University biomolecular archaeologist and one of the study’s co-authors, said efforts to eradicate Maya religious beliefs and activities – which included the systematic burning of thousands of Maya books and texts during the Spanish colonial period – had resulted in the destruction of much historical evidence.
“As a result, there are many gaps in our knowledge about the specific ritual practices performed by the ancient Maya – and especially their meaning,” she said. “Among these, human sacrifice remains one of the most misunderstood ritual acts.”