Danish linguists have achieved a breakthrough that could finally solve one of archaeology's greatest mysteries by deciphering the writing system of ancient Teotihuacan. The discovery reveals that the mysterious symbols adorning the walls of Mexico's "City of the Gods" record an early form of Uto-Aztecan language, fundamentally changing our understanding of who built this magnificent metropolis over two millennia ago.
Magnus Pharao Hansen and Christopher Helmke from the University of Copenhagen have presented compelling evidence in the prestigious journal Current Anthropology that Teotihuacan's colorful murals and artifacts contain a sophisticated writing system. Their research suggests this ancient script records a language that would later evolve into Nahuatl, the language of the Aztecs, along with Cora and Huichol languages still spoken today.
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The Rome of Ancient Mesoamerica
Teotihuacan flourished as a thriving metropolis from around 100 BC to 600 AD, housing up to 125,000 inhabitants at its peak. The ancient city, located just 30 miles (50 km) northeast of modern Mexico City, featured gigantic pyramids and served as a major cultural center throughout Mesoamerica. Despite its monumental architecture and widespread influence, the identity of its builders has remained one of archaeology's most persistent enigmas.
"There are many different cultures in Mexico. Some of them can be linked to specific archaeological cultures. But others are more uncertain. Teotihuacan is one of those places. We don't know what language they spoke or what later cultures they were linked to," explains Magnus Pharao Hansen in the University of Copenhagen announcement.
The researchers compare Teotihuacan's importance to that of Rome in the ancient Mediterranean world. Just as Rome served as the center of a vast empire, Teotihuacan held enormous cultural significance across ancient Mesoamerica. However, unlike Rome, whose history and people are well-documented, Teotihuacan has remained frustratingly anonymous – until now.
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Examples of logograms that make up the Teotihuacan written language. (Hanson/Helmke/Current Anthropology)
Decoding the Rebus System
The breakthrough came through analyzing the complex way Teotihuacan's writing system operated. The researchers discovered that the ancient scribes used a sophisticated combination of logograms and rebus principles. Some symbols function as direct representations – a coyote image simply means 'coyote' – while others operate as phonetic puzzles where the sounds of depicted objects combine to form entirely different words.
This dual system, which the researchers term "double spelling," required intimate knowledge of both the writing conventions and the spoken language. To crack this code, Hansen and Helmke had to simultaneously reconstruct the ancient Uto-Aztecan language while analyzing the visual symbols – a monumental linguistic archaeology project.
"It would be a bit like trying to decipher the runes on the famous Danish runestones, such as the Jelling Stone, using modern Danish. That would be anachronistic. You have to try to read the text using a language that is closer in time and contemporary," notes Christopher Helmke in describing their methodological approach.
The researchers worked backwards through time, reconstructing what the Uto-Aztecan language family might have sounded like during Teotihuacan's heyday. This linguistic reconstruction proved crucial for understanding how the rebus system worked, as the phonetic puzzles only make sense when you know how words were pronounced in antiquity.
Part of the restored Temple of Quetzalcoatl, the Feathered Serpent, at the Citadel in Teotihuacan in city of San Juan Teotihuacan, State of Mexico, Mexico. (Wangkun Jia/Adobe Stock)
Revolutionary Implications for Mesoamerican History
The implications of this discovery extend far beyond linguistics. If confirmed, this research would fundamentally alter our understanding of ancient Mexican civilizations and their relationships. The traditional narrative suggests that Nahuatl-speaking peoples, including the Aztecs, migrated to central Mexico after Teotihuacan's collapse around 600 AD.
However, the linguistic evidence now suggests that Uto-Aztecan speakers were present in the region much earlier than previously believed. This would make the Aztecs and other later civilizations direct descendants of Teotihuacan's builders rather than foreign arrivals who inherited an abandoned landscape.
"No one before us has used a language that fits the time period to decipher this written language. Nor has anyone been able to prove that certain logograms had a phonetic value that could be used in contexts other than the logogram's main meaning," Hansen explains, highlighting the innovation of their approach.
The research has already attracted significant attention from international experts in Mesoamerican studies. The Copenhagen team plans to host workshops to pool expertise from colleagues worldwide, recognizing that confirming their hypothesis will require collaborative effort from multiple disciplines.
Ancient murals at Teotihuacan contain the mysterious writing system being decoded. (Hanson/Helmke/Current Anthropology)
The Path Forward
Despite their breakthrough, the researchers acknowledge significant challenges ahead. The corpus of Teotihuacan texts remains relatively limited compared to other ancient writing systems like Maya hieroglyphs. "It is clearly a limitation to our research that we do not have more texts. It would be great if we could find the same signs used in the same way in many more contexts," Hansen notes.
Archaeological work continues at Teotihuacan, with new murals and inscribed pottery regularly emerging from excavations. Each new discovery provides additional data points that could either support or challenge the Copenhagen team's hypothesis. The researchers are particularly hopeful that future finds will reveal the same symbols used consistently across different contexts, strengthening their case for a genuine writing system.
The methodology developed by Hansen and Helmke represents a new baseline for approaching undeciphered Mesoamerican scripts. Their combination of historical linguistics and archaeological analysis offers a template that could potentially unlock other mysterious writing systems throughout the Americas.
Christopher Helmke emphasizes the broader significance:
"If we are right, it is not only remarkable that we have deciphered a writing system. It could have implications for our entire understanding of Mesoamerican cultures and, of course, point to a solution to the mystery surrounding the inhabitants of Teotihuacan."
Top image: Panoramic view of Teotihuacan in Mexico showing the ancient pyramids and ceremonial complex that housed up to 125,000 inhabitants at its peak between 100 BC and 600 AD. Source: Christophe Helmke/University of Copenhagen
By Gary Manners
References
Hansen, M. & Helmke, C. 2025. The Language of Teotihuacan Writing. Available at: https://www.journals.uchicago.edu/doi/abs/10.1086/737863?journalCode=ca
University of Copenhagen. 2025. Researchers on the verge of solving Mexican mystery. Available at: https://news.ku.dk/all_news/2025/10/researchers-on-the-verge-of-solving-mexican-mystery/
