Ancient genomes reveal which children the Maya chose for sacrifice

In the spring of 1967, workers building a small airport behind Chichén Itzá, the ancient Maya city in Mexico, ran into a problem: their excavations had uncovered human remains in the path of the proposed runway. The airport was set up to serve VIPs who wanted to visit Chichén Itzá. But with the remains so close to a major archaeological site, work had to stop until the bones could be examined.

Any hope of a quick solution was dashed when archaeologists called to the scene discovered a chultún – an underground rainwater storage vessel that, in Maya mythology, was seen as an entrance to the underworld of the dead. Connected to the cistern was a cave containing more than 100 sets of human remains, almost all of them belonging to children. In an effort to complete the airfield, researchers were given only two months to excavate and exhume the bone cache.

Nearly 60 years later, ancient DNA extracted from 64 of the children is providing new insights into ancient Mayan religious rituals and their connections to modern descendants. In a paper published Wednesday in the journal Nature, an international group of researchers found that the children — sacrificial victims killed between AD 500 and 900 — were all local Maya boys who may have been specifically selected to be killed. in sibling pairs.

“These are the first ancient Mayan genomes to be published,” said Johannes Krause, an archaeogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. The DNA work provided an unprecedented glimpse into the identities of the sacrificed children. “He feels very touched by such a discovery,” said Dr. Krause, noting that he himself has a young son.

Research into the Maya boys’ genome did not begin as an exercise in ancient Maya rituals. In the mid-2000s, Rodrigo Barquera—now an immunogeneticist at the Max Planck Institute—hoped to uncover the genetic legacy of Mesoamerica’s deadliest pandemic.

In 1545, an outbreak of Salmonella Enterica spread like wildfire in what is now Mexico. Over the next century, disease killed up to 90 percent of the indigenous population. Pandemics like these often leave a mark on the immune genes of survivors. To discover this genetic inheritance, Dr. Barquera and his colleagues had to compare the DNA from the pre-colonial remains with that of people born after the disaster.

The children found in the chultún were one such pre-Columbian group who probably never encountered the pandemic while they were alive. So in 2015, the team got permission to destroy a small part of their skull to sequence the DNA.

The team first used DNA to determine the sex of the children as part of routine sequencing. Skeletons of people under a certain age do not provide much information about biological sex, so this aspect of the children was a mystery.

It took a year for the first results to come in, and when they did, “Wow,” said Dr. Barquera.

All 64 skulls belonged to boys. “We kept doing the tests because we couldn’t believe they were all male,” he said. “It was just so amazing.”

Early archaeologists studying the Maya had proposed that the culture was preoccupied with the sacrifice of young virgin women. This theory has been challenged in recent decades by the discovery that most of the people sacrificed in the sacred cenote – a natural pit in Chichén Itzá – were children.

“This definitely countered the argument that it was mostly young virgin women jumping into cenotes,” said Jamie Awe, an archaeologist at Northern Arizona University in Flagstaff who was not involved in the study. The obsession with virgins in archaeological circles most likely arose from a combination of colonial ideas and limited data, he said.

Now, DNA confirms that the chultún children were all male, he said, adding: “We wouldn’t know who they were if the DNA study hadn’t been done.”

Subsequent genetic testing also showed that many of the boys were related, with two sets of identical twins among them. Why these boys were chosen for sacrifice is not known, said Dr. Barquera. But it is possible that the siblings, or close relatives, were chosen to reflect the trials of the Hero Twins, key figures in Maya cosmology who underwent cycles of sacrifice and rebirth.

“Rituals from ancient times tend to be special,” said Dr. Wow. “This study shows that for some religious ceremonies, it was important that only male children were chosen for sacrifice.”

The boys are now giving back to the modern Maya living around Chichén Itzá, Dr. Barquera and his colleagues. The team compared the boys’ DNA with that of Maya living in Tixcacaltuyub, a town about an hour’s drive from Chichén Itzá, and found strong genetic continuity between the two groups. As expected Dr. Barquera, the 1545 pandemic left its mark on the Maya, bequeathing the inhabitants of Tixcacaltuyub with at least one genetic variant associated with salmonella immunity.

Dr. Barquera and several colleagues traveled to Tixcacaltuyub to share their findings in local schools and with study participants. They also shared earlier genetic work done by other groups, showing that Mayan ancestors first moved into the region about 9,000 years ago. Taken together, the genetic work suggests that the peninsula’s vast population experienced little migration or genetic exchange since the earliest Mayan ancestors first moved.

The DNA provides “clear evidence that these people are descendants of people who developed one of the most advanced civilizations in the world,” said Dr. Wow.

Dr. Barquera added that study participants were thrilled to receive confirmation that they were genetically related to the builders of Chichén Itzá.

“People who live near these archaeological sites ask, ‘Why do you have so much respect for the people who built these sites and then treat the indigenous people who live around them as inferior?'” he said.

With these DNA results, he added, they can now say, “Look, we’re related to those who made these pyramids. So maybe stop being racist to us.”