Lasers were used to reveal the locations of America’s oldest known star calendars

The Olmec and Maya living on the Gulf Coast of Mexico first built ceremonial star-aligned centers 3,100 years ago to track the 260 most important days of the calendar, a new study finds.

The oldest written evidence of this calendar was found in painted ceiling mural fragments from a Maya site in Guatemala, dating to between 300 and 200 BC, nearly a millennium later.SN: 4/13/22). But researchers have long suspected that the Gulf Coast Olmecs advanced 100 years before the 260 calendar days.

Now, an aerial laser-spotting technique that uses light detection and ranging, or lidar, has revealed the astronomical orientations of 415 ceremonial complexes that were dated between about 1100 BC and AD 250, say archaeologist Ivan Prajc and colleagues. Most ritual centers were aligned on an east-west axis, corresponding to sunrise or other celestial events on specific days of the 260-day year, scientists report on January 6. Journal of Sciences.

The discovery points to the first evidence of a formal calendar system in the Americas that combined astronomical knowledge with terrestrial constructions. This system of celestial objects was used to determine the exact moments during the 260 days of the entire year.

“The 260-day cycle materialized in Mesoamerica’s early not the monumental complexes” [and was used] to the scheduling of seasonal, subsistence-related ceremonies,” says Šprajc, from the Research Center of the Slovenian Academy of Sciences and Arts in Ljubljana. “We cannot be absolutely certain when and where it was found.”

Some of the oldest ceremonial centers identified by lidar clearly belong to the Olmec culture, but others are difficult to pin down, says archaeologist Stephen Houston of Brown University in Providence, RI, who was not involved in the new study.

The Olmec society lasted from about 3,500 to 2,400 years ago. The connections between the Olmec and the later Maya culture, best known for the Classic-era cities and kingdoms that flourished between about 1,750 and 1,100 years ago, are obscure. However, the Mayan classics and documents also refer to the 260-day calendar.

Mobile groups in Mesoamerica, an ancient cultural region that extended from central Mexico into Central America, using large, seasonal meetings, 260 today’s calendar long before the time it won favor with the Mayan kings, Šprajc and colleagues. The same calendar can also be used to mark the dates of important agricultural activities or rituals such as the farre culture that spread in Mesoamerica, beginning around 3,000 years ago. Some Mayan communities still use the 260 day calendar to organize maize cultivation and agricultural rituals.

Previous lidar data indicated that ceremonial centers appeared on a common blueprint for many Olmec and Maya sites along the Gulf Coast of Mexico by about 3,400 years ago (SN: 10/25/21). It is only now that the significance of the ceremonial centers of “ceremonial alignments” is revealed.

The most frequent architectural nights detected in the new study were the positions of the sun on February 11 and October 29, when the complexes were in use, separated by 260 days. These complexes look east towards the point above the horizon where the sun rose on those two days.

Another orientation equaled the frequent rising of the sun on 130 separate days, or half of the 260 days.

A minority of ceremonial complexes aligned with solstices (the longest and shortest days of the year), quarter days (the middle of each half of the year) or lunar cycles in the 260-day year. The rest of the seat of Friday was examined, the star associated with the rainy season and the country’s corn.

Risings or settings are recorded in ceremonial centers typically separated by multiples of 13 or 20 days. In addition to representing the basic mathematical units of the 260-day year, the numbers 13 and 20 have long been associated with various gods and sacred concepts among Mayan people and other Mesoamerican groups, Šprajc says.

Future excavations at lidar-detected ceremonial complexes may investigate whether groups of ancients formally dedicated any structures on specific days in the 260-day year, Houston says.