Ancient genomes reveal insights into ritual life at Chichén Itzá

The ancient city of Chichén Itzá in Yucatán, Mexico was one of the largest and most influential Maya settlements during the Late and Terminal Classic periods (AD 600-1000), and it remains one of the most intensively-studied archaeological sites in Mesoamerica1–4. However, many questions regarding the social and cultural use of its ceremonial spaces, as well as its population's genetic ties to other Mesoamerican groups, remain unanswered2. Here, we present genome wide data obtained from 64 subadult individuals dating to ca. AD 500-900 that were found in a subterranean mass burial near the Sacred Cenote (sinkhole) in the ceremonial centre of Chichén Itzá. Genetic analyses revealed that all analysed individuals were male, and several individuals were closely related, including two pairs of monozygotic twins. Twins feature prominently in Mayan and broader Mesoamerican mythology, where they embody qualities of duality among deities and heroes5, but until now they had not been identified within ancient Mayan mortuary contexts. Genetic comparison to present day people in the region reveals genetic continuity with the ancient inhabitants of Chichén Itzá, except at certain genetic loci related to human immunity, including the HLA complex, suggesting signals of adaptation due to infectious diseases introduced to the region during the colonial period.