William Saturno, a Boston University archeologist, excavates a mural in a house in Xultun, massive Mayan ruins in Guatemala. The mural depicts a figure who may have been the town scribe. Excavation and preservation of the site were supported by the National Geographic Society. (Photo by Tyrone Turner © 2012 National Geographic)
William Saturno, a Boston University archeologist, excavates a mural in a house in Xultun, massive Mayan ruins in Guatemala. The mural depicts a figure who may have been the town scribe. Excavation and preservation of the site were supported by the National Geographic Society. (Photo by Tyrone Turner © 2012 National Geographic)

In the rainforest-covered ruins of a Mayan city dating back more than 1,100 years, a Boston University-led excavation has turned up the oldest evidence of that civilization’s mastery of astronomy—a precise lunar calendar scrawled on what appears to be an ancient blackboard.

The calendar, consisting of delicately-painted symbols and columns of numbers, was one of a number of texts found on the wall of a room in a residential area of the massive complex of ruins called Xultun in northeast Guatemala, the scientists reported Thursday in the journal Science. It’s four to five centuries older than previous Mayan calendars, and the earliest found on a wall rather than in books.

The small room where it was found may have been a kind of office for Mayan scribes. With numbers and glyphs scrawled along the wall and over sections of a mural, it suggests scribes had sophisticated knowledge of astronomy and mathematics as early as the ninth century.

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Scholars who study the Maya said the well-preserved room provides insights into the people’s lives beyond those drawn from the more lasting stone monuments and artifacts that archeologists often depend on to reconstruct ancient civilizations. It’s almost as if the researchers can peer over the shoulders of the scribes who were writing and thinking there. The BU-led team reported sections of the wall had been plastered over to make space for new text.

“For me what’s really amazing is people are erasing and changing it and adapting it,” said Charles Golden, associate professor of anthroplogy at Brandeis University, who was not involved in the research. “You get these works in progress that really humanizes this, it kind of demystifies it.”

Another set of numbers painted on a section of wall undermines an idea that has been embraced in popular culture—including the movie “2012”—that the Maya predicted the world would end in “13 baktuns” or about 5,000 years, which works out to the end of 2012. That idea has long been dismissed by scholars, who explain that the Maya calendar is like a car’s odometer that turns over when it reaches that date, not a doomsday prediction. The new find reinforces that the Maya’s conception of time was not finite, because it contains a calendar that extends 17 baktuns, about 7,000 years.

The Maya lived in Mexico and Central America, and were a dominant force in that area, with a written language and an understanding of astronomy and calendars. Their civilization, known for stepped pyramids, spanned from about 2000 B.C. to the arrival of the Spanish about 3,500 years later.

The room was uncovered by a combination of chance and persistence. A determined BU undergraduate, Maxwell Chamberlain, spotted a faded painting on a patch of wall during his lunch break, while exploring trenches dug by looters. William Saturno, an assistant professor of archeology at BU who led the team, began an excavation, and discovered a magnificent, nearly life-sized portrait of a Maya king, adorned with a brilliant blue feather head-dress. Further excavation, supported by the National Geographic Society, revealed a row of mysterious figures and one badly-damaged wall, which was covered with writing.

Eventually, a Sudoku-like analysis, using information about what numbers were visible in the table to calculate what numbers the rest of the table must have contained, revealed that the incomplete table was a 13-year lunar calendar. Another set of numbers, the scientists report, seem to record other astronomical and planetary events.

“We find inside this city that’s been known about for a century, in this little house on the outskirts of town ... all these numbers and writings and calculations that involve both the calendar and astronomy and observations and history and the preparations of texts,” Saturno said.

The modest room has only begun to yield its secrets, with more texts yet to be deciphered. Marc Zender, a visiting assistant professor of anthropology at Tulane University not involved in the research, compared the work to being able to see the notes and scribblings that led to famous mathematical theorems.

“These astronomical tables are written across some figures at interesting angles, only in the part of the room where light falls through the doorway,” Zender said. Most likely scribes were at work in the room, and “they were probably consulting books, but maybe it was getting onerous to flip through the book; they may have simply copied them on to the wall so they didn’t have to keep opening their bark-paper books.”

Zender said he hoped to use the tables to look at monuments left behind by the Maya at other sites, to understand whether mathematical and astronomical understanding and calendars were centralized, or whether they were being derived and calculated in different regions of the Mayan empire.

Saturno said he is investigating whether imaging might be used to reveal what is written beneath areas that have been plastered over. The room has a recessed niche in the back, where the king’s portrait sits, and the archeologists found evidence of a bone rod that would have held a curtain that could cover up the image of the king. On the same wall is a second mysterious figure, a vividly-painted man who holds a stylus in a hand—perhaps a scribe who worked in the room.

“It’s an astonishing discovery,” said Stephen Houston, a professor of anthropology and archeology at Brown University. Such calculations and tables appear in books from about 500 years later, but “here, we see them instead, painted with some care I might add, in what might seem to be an arbitrary arrangement in an elite chamber.” He said the find raises difficult questions about what the scribes were up to, including why they would have written the tables on the wall.