The Olmecs and Mayas, who lived along the Gulf Coast as far back as 3,100 years ago, built ceremonial centers aligned with the stars to keep track of important days in the 260-day calendar, a new study has found.
The oldest written proof of this calendar , found on fragments of painted plaster wall paintings from a Mayan settlement in Guatemala, dates to between 300 and 200 BC, nearly a millennium later. But researchers have long suspected that the 260-day calendar was developed hundreds of years ago among the Olmec groups of the Gulf Coast.
According to archaeologist Ivan Shpraits and his colleagues, astronomical orientation of 415 ceremonial complexes dating from approximately 1100 BC. Most of the ritual centers were located along an axis from east to west, according to sunrises or other celestial events on certain days of the 260-day year, scientists reported on January 6 in Science Advances .
The find points to the earliest evidence of a formal calendar system in the Americas that combined astronomical knowledge with earthly structures. This system used celestial events to determine important dates during the 260-day portion of a full year.
“The 260-day cycle materialized in the oldest known monumental complexes of Mesoamerica [і використовувався] for planning seasonal ceremonies related to sustenance,” says Sprejc from the Research Center of the Slovenian Academy of Sciences and Arts in Ljubljana. “We cannot say exactly when or where it was invented.”
Some of the earliest ceremonial centers identified by lidar clearly belong to the Olmec culture, but others are difficult to classify, says archaeologist Steven Huston of Brown University in Providence, Rhode Island, who was not involved in the new study.
Olmec society dates back to approximately 3500-2400 years ago. The connections between the Olmec and the later Maya culture, best known for the Classic Era cities and kingdoms that flourished from about 1750 to 1100 years ago, are unclear. But Classic Maya inscriptions and documents also mention a 260-day calendar.
Mobile groups in Mesoamerica, the ancient cultural region that stretched from central Mexico to Central America, may have planned large seasonal gatherings around the 260-day calendar long before it gained favor among Classic Maya kings, Spreitz and his colleagues suggest. The same calendar may also mark days of important agricultural work or rituals, since maize cultivation spread to Mesoamerica around 3,000 years ago, they add. Some Mayan communities still use a 260-day calendar to organize corn cultivation and plan agricultural rituals.
Preliminary lidar data showed that ceremonial centers based on a general plan appeared at many Olmec and Maya sites along the Gulf Coast about 3,400 years ago. Only now has the calendar significance of the location of ceremonial centers become obvious.
The most common architectural alignment found in the new study corresponded to the positions of the sunrises on February 11 and October 29, when the complexes were in use, separated by 260 days. These complexes were facing east to the point on the horizon where the sun rose on those two days.
Another frequent orientation coincided with dawns separated by 130 days, or half of 260 days.
A minority of ceremonial complexes aligned with the dates of the solstices (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. Other centers tracked the position of Venus, the star associated with the rainy season and corn farming.
The sunrise and sunset recorded in the ceremonial centers were usually 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 the Maya and other Mesoamerican groups, Spreitz says.
Future excavations at ceremonial complexes uncovered by lidar could investigate whether ancient groups formally dedicated certain structures to certain days in the 260-day year, Houston says.
