On 21 July 1561, a crowd of indigenous farmers cried out in the town square of Maní, Mexico, as a Franciscan missionary set fire to dozens of fragile Maya books, or codices. Condemned by the missionaries as "the Devil's trickery," these written texts preserved knowledge gleaned from centuries of Maya science and mathematics. Similar acts of destruction followed, obliterating hundreds of other Maya codices. Today, only a handful of readable, precolonial codices survive.
Now a team of American researchers has discovered a small trove of ancient Maya texts in a surprising place. In a paper published online today in Science, William Saturno, an archaeologist at Boston University, and his colleagues, report finding Maya astronomical tables and other texts painted and incised on the walls of a 1200-year-old residential building at the site of Xultún in Guatemala. The newly discovered astronomical tables are at least 500 years older than those preserved in the Maya codices, giving researchers a new glimpse of science at the height of the Maya civilization. "I think we are all astonished by this find," says Stephen Houston, an archaeologist at Brown University who was not part of the team.
Looters have extensively targeted Xultún, which was once a sprawling Maya city-state. But in March 2010, a member of Saturno's team, Boston University student Maxwell Chamberlain, discovered part of a painted wall exposed by the illicit diggers. Subsequent archaeological excavation revealed three intact room walls within a residential compound: the walls bore paintings of human figures—including an elaborately attired Maya king—as well as vertical columns of numbers written in Maya hieroglyphs.
The team scanned all of the paintings and numbers, digitally stitched them together, and sent the images to epigrapher David Stuart of the University of Texas, Austin, who specializes in studying Maya inscriptions. Stuart's analysis revealed that at least five of the numerical columns were topped by hieroglyphs that Maya scribes once used to record lunar data. These "moon" glyphs, as well as the patterns of numbers below them, suggest that the columns represent astronomical notations similar to the Eclipse Table in the Dresden Codex, a Maya book now housed in a German museum. Other numerical groupings in the recently discovered room appear to represent calendrical cycles involving the planets Venus and Mars.
Maya scribes used their knowledge of astronomical cycles to plan important public ceremonies such as the accession to power of a Maya king or the naming of a royal heir. "The Maya liked to anchor their historic events in cosmic time," says Saturno. So Maya scribes relied on calendrical knowledge to schedule key ceremonies on the most appropriate dates, such as a day when an important mythical event was said to take place or an astronomical phenomenon such as an eclipse occurred.
But why did someone record the astronomical tables on residential walls rather than on bark paper, as Maya scribes generally did? One of the incised texts suggests that the room was in use around 813 C.E., and Houston thinks this date may offer a clue. During the early 9th century, political turmoil wracked parts of the Maya world, with some city-states imploding as others seemed to rise. Perhaps, Houston suggests, the Xultún scribe wished to make a more permanent record of calendrical data. "It could be kind of a drive toward archiving," he says.
All in all, it looks like a remarkably prescient decision given the later loss of most Maya books. And the fresh view that this unusual archive affords into the minds of ancient Maya scientists is a particularly enthralling one, says Houston. "What you are looking at here is a fundamental human drive to make sense of the disparate patterns of nature,  and somehow harmonize them into an elegant mathematical structure."