In the spring of 1967, workers building a small airport behind the ancient Mayan city of Chichen Itzá in Mexico ran into a problem. During the excavation, human remains were discovered in the intended runway corridor. The airport is set up to serve VIPs wishing to visit Chichén Itzá. But the ruins were so close to a major archaeological site that work had to be halted until the bones could be examined.
All hope for a quick solution was lost when archaeologists sent to the site discovered the chultún. A chultun is an underground rainwater storage vessel believed to be the entrance to the underworld of the dead in Mayan mythology. The cave connected to the cistern contained more than 100 sets of human remains, almost all of them children. To complete the airport, researchers were given just two months to excavate and excavate the bones.
Nearly 60 years later, ancient DNA extracted from 64 children is providing new insights into ancient Mayan religious rituals and their relationship to modern descendants. In a paper published Wednesday in the journal Nature, an international group of researchers found that the victim children killed between 500 and 900 AD were all local Mayan boys who may have been specifically selected to be killed in brother-sister pairs.
“This is the first ancient Maya genome to be published,” said archaeologist Johannes Krause of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. DNA research has provided a previously unseen glimpse into the identities of the victims. “I was very touched by these findings,” said Dr. Krause, noting that he has a young son.
The search for the Mayan boy’s genome did not begin with the practice of ancient Mayan rituals. In the mid-2000s, Rodrigo Barquera, now an immunogeneticist at the Max Planck Institute, was hoping to discover the genetic legacy of Mesoamerica’s deadliest infectious disease.
In 1545, Salmonella enterica spread like wildfire throughout what is now Mexico. Over the next century, the disease killed up to 90% of the indigenous population. Infectious diseases like these often leave their mark on the immune genes of survivors. To uncover this genetic legacy, Dr. Barquera and his colleagues had to compare DNA from pre-colonial remains with that of people born after the disaster.
The children discovered at Chultun were among a pre-Columbian group that had never encountered an infectious disease in their lifetime. So in 2015, the team received permission to destroy a small section of the skull for DNA sequencing.
The research team first used DNA to determine the children’s gender as part of routine sequencing. This aspect of children has been a mystery because the skeletons of people under a certain age do not provide much information about biological sex.
It took a year for the first results to come back, and when they did, Dr. Barquera said, “Wow.”
All 64 skulls belonged to boys. “We kept re-doing the tests because we couldn’t believe they were all male,” he said. “It was really amazing.”
Early archaeologists studying the Maya suggested that the Mayan culture was preoccupied with sacrificing young virgin women. This theory has been challenged in recent decades with the discovery that most of the victims in Chichen Itza’s sacred cenote, a natural sinkhole, were children.
“It flies in the face of the argument that the people thrown into the cenotes were mostly young virgin women,” said Jaime Awe, an archaeologist at Northern Arizona University who was not involved in the study. The archaeological community’s obsession with virgins likely stems from a combination of colonial ideas and limited data, he said.
DNA now confirms that Chultun’s children were all male, he added. “If DNA research hadn’t been done, we wouldn’t have known who they were.”
Subsequent genetic testing also showed that many of the boys were related, including two sets of identical twins. Dr Barquera said it was unknown why these boys were chosen for sacrifice. However, it is possible that siblings or close relatives were chosen to reflect the trials of the twin heroes, key figures in Maya cosmology who underwent a cycle of sacrifice and reincarnation.
“Rituals from ancient times tend to be special,” Dr. Awe said. “This study shows that in some religious rituals it is important to select only male children as sacrifices.”
Dr. Barquera and his colleagues say the boys are now donating to the modern Maya living around Chichén Itzá. The team compared the boys’ DNA with that of the Maya from Tixcacaltuyub, a village about an hour’s drive from Chichen Itza, and found strong genetic continuity between the two groups. As Dr. Barquera predicted, the 1545 epidemic left its mark on the Maya, leaving Tixcacaltuyub residents with at least one genetic variant associated with salmonella immunity.
Dr. Barquera and several colleagues visited Tixcacaltuyub to share their results with local schools and study participants. They also shared previous genetic research conducted by other groups that indicated Mayan ancestors first migrated to the region about 9,000 years ago. Collectively, genetic work suggests that many of the peninsula’s populations have experienced little migration or genetic exchange since the early ancestors of the Maya first migrated.
DNA provides “clear evidence that these people are descendants of people who developed one of the world’s greatest civilizations,” Dr. Awe said.
Dr. Barquera added that he was very pleased to receive confirmation that the study participants were genetically related to the builders of Chichén Itzá.
“People who live near these archaeological sites ask, ‘Why do we have so much respect for the people who built these sites, and treat the indigenous people who live around them like inferior people?’” he said.
He added that with these DNA results we can now say: “Look, we are related to the people who built these pyramids. So please stop being racist towards us.”
