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 Mesoamerica. However, many questions about the social and cultural use of its ceremonial spaces, as well as its population’s genetic ties to other Mesoamerican groups, remain unanswered.
Here we present genome-wide data obtained from 64 subadult individuals dating to around 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 showed 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 heroes, but until now they had not been identified in ancient Mayan mortuary contexts. Genetic comparison to present-day people in the region shows genetic continuity with the ancient inhabitants of Chichén Itzá, except at certain genetic loci related to human immunity, including the human leukocyte antigen complex, suggesting signals of adaptation due to infectious diseases introduced to the region during the colonial period.
The ancient Maya city of Chichén Itzá, centrally located in the northern part of the Yucatán Peninsula, ranks among the largest and most iconic archaeological sites in Mesoamerica but much about its origins and history remains poorly understood.
First rising to prominence during the Late Classic period (ad 600–800), Chichén Itzá became the dominant political centre of the northern Maya lowlands during the Terminal Classic (ad 800–1000), a period when most other Classic Maya sites in the southern and northern lowlands underwent a political collapse. Most of the inscribed calendar dates on carved monuments at Chichén Itzá fall between ad 850 and 875 and the northern ceremonial centre of the site, known as New Chichén, was largely constructed after ad 900 and includes the site’s largest structure, El Castillo, also known as the Temple of Kukulkán. A sacbe (limestone causeway) was constructed to connect New Chichén to the Sacred Cenote6, an enormous sinkhole containing abundant ritual offerings, including the remains of more than 200 ritually sacrificed individuals, mostly children. Evidence of ritual killing is extensive throughout the site of Chichén Itzá and includes both the physical remains of sacrificed individuals as well as representations in monumental art. Elite activity at Chichén Itzá declined during the eleventh century ad, with a last inscribed calendar date of ad 998, but the site continued to be a prominent ritual and pilgrimage centre during the colonial period and beyond.
In 1967, a repurposed chultún containing the remains of more than 100 subadults was discovered near the Sacred Cenote. As for cenotes, chultúns (underground cisterns) are associated with water storage and also ritual activity and they share symbolism with caves. Such subterranean features have long been associated with water, rain and child sacrifice and they are widely viewed as access points to the Maya underworld. Given the location and context of the Chichén Itzá chultún, which was also connected to a small underground cave, it has been speculated to contain children sacrificed to support maize agricultural cycles or given as offerings to the Maya rain deity Chaac. Sixteenth century Spanish colonial accounts and early twentieth century investigations following the dredging of the Sacred Cenote popularized the notion that young women and girls were primarily sacrificed at the site but more recent osteological analyses indicate that the bodies of both males and females were deposited in the Sacred Cenote. Systematic investigations of sacrificial assemblages across the Maya region have confirmed that both males and females were subject to ritual killing but, because most sacrificed individuals at Classic Maya sites are juveniles, precise sex distributions cannot be determined using conventional osteological approaches alone. Sixteenth century Spanish sources record that such children were obtained locally by kidnapping, purchase and gift exchange, although recent isotopic studies suggest that at least some individuals within the Sacred Cenote were non-local and may have originated as far away as Honduras or Central Mexico. Nevertheless, despite more than a century of research, much about child sacrifice and the ceremonial use of subterranean features as ritual mass graves at Chichén Itzá remains unknown.
To better understand the origin and biological relationships of the sacrificed children to each other and to present-day inhabitants of the region, here we used a combined bioarchaeological and genomics approach to investigate 64 subadults interred within a chultún near the Sacred Cenote and compare them to 68 present-day Maya inhabitants of the nearby town of Tixcacaltuyub, as well as to other available ancient and contemporary genetic data from the region. The community of Tixcacaltuyub has been collaborating with our research team for many years and their perspectives informed the development of this manuscript. Our analyses, comprising of ancient human genetic data analysis, bone collagen stable isotope analysis of carbon and nitrogen and radiocarbon dating show that all chultún subadults were male and that close relatives were present in the mass burial, including two sets of monozygotic twins. Stable isotope analysis indicates that related children consumed more similar diets and that overall the diet of Chichén Itzá children was comparable to that of other Classic period populations throughout the Maya Lowlands. Genetic comparison to other ancient and present-day people shows long-term genetic continuity in the Maya region but indicates allele frequency shifts in immunity genes at the human leukocyte antigen (HLA) class II locus, specifically an increase in HLA-DR4 alleles which provide greater resistance to Salmonella enterica infection, the causative agent of an enteric fever previously identified in a colonial-era mass grave in Oaxaca, southern Mexico, which was associated with the 1545 cocoliztli pandemic.
Republished courtesy of Nature.