A decade after its discovery in the Historic Center of Mexico City, the Huei Tzompantli of Tenochтιтlan—an immense structure built with human skulls—continues to yield new knowledge about Mexica society and ritual. Uncovered in 2015 by the National Insтιтute of Anthropology and History’s (INAH) Urban Archaeology Program (PAU), the tower remains one of the most spectacular archaeological finds in the capital’s colonial subsoil.
Replica of a tzompantli in the Museo Nacional de Historia in Mexico City. Credit: Raulhdxtrejo / CC BY-SA 4.0
Although excavations at the site on 24 Guatemala Street were finished years ago, the project has entered an intensive laboratory phase at the Templo Mayor Museum (MTM). There, a sample of 214 skulls, carefully cleaned, stabilized, and restored, is being analyzed with the expertise of the Bioarchaeology and Genetics laboratories of the National School of Anthropology and History (ENAH).
Two complementary projects are underway. The first is stable isotope analysis of carbon, oxygen, and strontium in the first molars of skulls that still retain them. Food and drink consumed in early childhood may contain chemical markers capable of providing information about where individuals were born. Eighty-three samples of skulls have been sent to the University of Georgia in the USA, thanks to funding from Mexico’s Ministry of Culture.
The second project delves into ancient DNA. Bone samples are processed at ENAH before being sent to the Max Planck Insтιтute (MPI) in Germany, a global leader in paleogenomics. Under an INAH–MPI agreement, Mexican biochemist Rodrigo Barquera, a graduate of ENAH and now a member of the MPI staff, is collaborating with physical anthropologist Víctor Acuña to help rebuild the genetic profiles of the individuals.
Model of the Tzompantli (skull rack) of the Tenochтιтlan Ceremonial Center, National Museum of Anthropology, Mexico City. Credit: Gary Todd
It is necessary to preserve the in situ structure. MTM conservation specialists and physical anthropologists also monitor the tzompantli closely in order to detect deterioration and initiate long-term protective measures.
Addressing the structure was difficult. Unlike European ossuaries—where skulls are arranged decoratively, such as in Portugal’s Chapel of Bones or Paris’s Catacombs—the Huei Tzompantli incorporated skulls into its construction system. Before studying intact examples, the team removed around 11,000 bone fragments related to the tower’s five building phases.
Initial analysis indicates that 46.3% of the skulls are male, 37.4% female, and the rest are incomplete or belong to children. The fact that there are no parietal perforations on child skulls implies different treatment, since drilling would have destroyed them. For adults, the question remains: how were mandibles retained in place after soft tissues were removed as part of ritual preparation?
Preserved and untouched by post-burial animal disruption, the skulls bear witness to a highly skilled process.
