Carbon-14 Dating Suggests Popotla Map is a 1950s Copy, Not 16th-Century Original 1

Preliminary radiocarbon dating results for the Popotla Map, an artifact held at the National Library of Anthropology and History (BNAH), indicate a significant revision to its assumed age, suggesting the analyzed skin material dates to approximately 1950. This finding challenges the long-established attribution of the document to the 16th century, a view largely based on the 1947 description by archaeologist Alfonso Caso, who characterized it as a pre-Hispanic codex. Anthropologist Isabel Bueno, leading the current investigation, confirmed the preliminary 1950 result, noting that scholarly consensus has historically relied on Caso’s earlier designation.

Bueno began her engagement with the pictographic codex in 2010, and physical analysis permits were secured from the National Institute of Anthropology and History (INAH) in July 2025. The comprehensive, multidisciplinary study employs codicological methods, including forensic lighting, chemical pigment analysis, and microscopic fiber structure examination. Chemical assessment of the map’s coloration revealed the presence of lead and arsenic, substances often incorporated into modern paint formulations, which lends credence to the more recent dating. This evidence strongly implies that the material examined is a contemporary reproduction of an original document whose current location remains unknown.

Research led by Bueno suggests the original codex should have been cataloged in the National Museum by 1866, following an order from Emperor Maximilian for its creation. Historical records indicate that Dominik Bilimek, who directed the National Museum after Maximilian’s execution in 1867, may have been responsible for transferring certain copies to Europe. The ongoing study, which includes specialists from the National Autonomous University of Mexico (UNAM) and the University of Warsaw, is projected to conclude in early 2026.

The investigation has already documented at least three versions besides the analyzed skin: a tracing from 1720 by Gómez de Orozco on semi-transparent paper, and a third version on 20th-century albanene paper, potentially commissioned by Caso in the late 1940s. Furthermore, two additional copies are documented as being held in Vienna, specifically within the Map Department of the Austrian National Library, which is recognized as a major global institution for cartographic collections. Bueno views this result as an opportunity for scholarly correction, suggesting that indigenous cartography requires a reading fundamentally different from the one assumed by Caso, necessitating a reinterpretation of the depicted spatial relationships.

To seek a definitive resolution to the provenance mystery, the team has requested a contrasting sample from INAH to compare with the initial radiocarbon measurements. Progress is scheduled for dissemination at a colloquium organized by INAH for Friday, November 28, 2025, at the National Museum of Anthropology. The Viennese copies, noted for superior preservation, have aided the research by revealing subtle nuances lost in the Mexican reproductions. Bueno theorizes the original map may derive from a "primordial title," a legal instrument used by the inhabitants of Popotla to assert land claims.