New scientific analysis has confirmed that the Aubin Tonalámatl Codex, an important Indigenous Mexican divinatory manuscript, dates from before the Spanish conquest, with researchers proposing 1494 as its most likely year of production.
Carbon-14 dating has provided new evidence that the manuscript was created during the late 15th century, resolving a long-running debate over whether the codex was genuinely pre-Hispanic or produced during the colonial period.
The findings are presented in the new publication Tonalámatl de Aubin: New Studies on a Divinatory Codex, which was unveiled on 29 August 2026 at the International University Book Fair.
Baltazar Brito Guadarrama, head of Mexico’s National Library of Anthropology and History (BNAH), said the scientific analysis indicates that the manuscript was produced no earlier than around 1450. Taking into account the range generated by radiocarbon dating, researchers have proposed 1494 as the most likely date.
“From a scientific point of view, it is a pre-Hispanic manuscript, which is relevant,” Brito said.
Scientific dating sheds new light on the codex
The dating project was conducted through a collaboration between the BNAH and the University of Colorado Boulder in the United States.
Researchers propose 1424 as the most likely date for the acquisition or preparation of the manuscript’s raw material, with the codex itself subsequently produced towards the end of the 15th century.
The study also reconstructs what may have happened to the manuscript after the Spanish conquest.
Originally associated with divination and the interpretation of destinies, the codex appears to have continued to circulate clandestinely during the colonial era, when Indigenous religious manuscripts faced suppression by Spanish authorities.
In a chapter examining accelerator mass spectrometry carbon-14 dating of the manuscript, Brito and University of Colorado archaeologists Gerardo Gutiérrez and William Taylor argue that the codex may have been deliberately hidden sometime between 1614 and 1648.
Italian historian and antiquarian Lorenzo Boturini is believed to have learnt of its existence and acquired it around 1740.
A manuscript hidden for generations
The researchers suggest that the Aubin Tonalámatl entered the colonial period as a prohibited religious text.
Its concealment may therefore represent more than an attempt to preserve an old manuscript. According to the study, keeping the codex hidden from Spanish authorities can be interpreted as a form of Indigenous resistance to the religious system imposed following the conquest.
Its continued preservation potentially helped sustain elements of the pre-Hispanic worldview for approximately two centuries after Spanish rule began.
The codex’s true age had previously been the subject of considerable uncertainty. Some scholars had regarded it as a roughly executed copy of the Codex Borbonicus, another important Mesoamerican manuscript, while others had raised the possibility that it was a colonial-era imitation.
Certain artistic characteristics also complicated efforts to establish its origins, including the depiction of the “flower” glyph and the layering of colours within its pictographs.
The new radiocarbon evidence now provides scientific support for placing its production firmly within the pre-Hispanic period.
New research into materials, pigments and imagery
The newly published volume brings together research by 16 specialists in physics, chemistry, biology, archaeology and history.
Co-published by Mexico’s Ministry of Culture through the National Institute of Anthropology and History (INAH), together with the National Autonomous University of Mexico, the book grew out of a symposium held in 2023 at the National Museum of Anthropology and the Institute of Historical Research.
Alongside the carbon-dating results, researchers examine the provenance of the materials used to manufacture the codex, the origins and composition of its pigments, and evidence of pentimenti — alterations or corrections made during the manuscript’s creation.
The volume also examines representations of deities and compares the manuscript with the Codex Borbonicus, which shares similarities in its religious and divinatory subject matter and pictographic traditions.
An 18-sheet guide to the 260-day calendar
The Aubin Tonalámatl Codex consists of 18 sheets of amate paper, each measuring approximately 24 by 27 centimetres.
The sheets form a continuous strip approximately 4.86 metres long, folded accordion-style to create a screenfold manuscript.
Unlike some comparable manuscripts, its amate paper does not carry the coating known as chimaltizatl.
Its pictographs record information connected with the tonalpohualli, the sacred 260-day calendrical cycle used in central Mexico. The manuscript depicts deities and other symbols associated with successive 13-day periods within that cycle.
The new dating evidence substantially strengthens the case that these images were produced before the Spanish conquest, making the Aubin Tonalámatl an important surviving witness to the religious, calendrical and divinatory traditions of pre-Hispanic Mexico.
Sources : INAH
