Science

Nearly 500 Mesoamerican monuments revealed by laser mapping—many for the first time

Scientists have uncovered nearly 500 Mesoamerican monuments in southern Mexico using an airborne laser mapping technology called lidar. Dating as far back as 3000 years ago, the structures—still buried beneath vegetation—include huge artificial plateaus that may have been used for ceremonial gatherings and other religious events.

“The sheer number of sites they found is staggering,” says Thomas Garrison, an archeologist at the University of Texas, Austin, who was not involved in the work. “The study is going to be the inspiration for hopefully decades of research at these different settlements.”

The team’s effort stemmed from its smaller scale lidar survey and excavation of the oldest and largest Maya structure ever found, reported in Nature last year. The ancient Maya civilization occupied southern Mexico and parts of Central America and is renowned for its striking pyramids, written language, and calendar system. That site, dubbed Aguada Fénix, was dated to 1000 to 800 B.C.E., and contained an artificial plateau 1400 meters long and up to 15 meters high. This plateau had 10 smaller platforms flanking either side for a total of 20—the basis for many Mesoamerican cultures’ number system.

The number 20 is also important in the Mesoamerican cosmology and calendar, and the same pattern of a large plateau flanked by smaller platforms appears at other sites in the immediate region, suggesting a wider cultural pattern. The team wanted to see how common the arrangement was across an even wider area. But lidar studies can be pricey.

So, the researchers utilized publicly available lidar data already collected by the Mexican government to survey roughly 84,500 square kilometers. Such data typically aren’t used for archeology because of the low resolution—lidar produces images at a 5-meter scale rather than the 1-meter or even 50-centimeter scale typical in archeological surveys. However, the researchers were able to compare the government data with higher resolution maps at certain sites, and also visited some of the revealed structures by foot.

The analysis resulted in the discovery of 478 formal complexes—many new to science—the team reports today in Nature Human Behaviour. Several of these monuments had the same layout as Aguada Fénix, including an even more ancient Olmec site in San Lorenzo. Researchers continue to argue over whether the Olmec, which predate the Maya, are more of a mother or sister culture to them. The researchers estimate these Olmec and Maya complexes were built between 1100 and 400 B.C.E., and would have been used for ceremonial gatherings.

A survey covered an 84,500-square-kilometer region containing Maya and Olmec settlements built between 1100 to 400 B.C.E.Takeshi Inomata

This surprising discovery suggests San Lorenzo was the inspiration for the late Maya sites, including Aguada Fénix, says Takeshi Inomata, an archeologist at the University of Arizona who led the study. “People thought San Lorenzo was very unique, and that there was not much connection to what came later,” he says. He adds that the find could push the origin of the base-20 Mesoamerican calendar system hundreds of years earlier than written evidence of calendars appears. “This find forces us to rethink what’s happening during this period,” Inomata says. It’s a “compelling argument,” Garrison adds.

The team also found four additional layout types, representing either different cultural influences or different points in time. “It’s amazing to have missed so many of these complexes,” Garrison says. Some of them, he says, are “so massive that they’re hiding in plain sight.”

These new regionwide data raise some tantalizing questions. The standardized ceremonial center layouts indicate this kind of architecture was formalized earlier than researchers thought. Inomata notes that there is scant evidence for permanent residences prior to about 500 B.C.E. and suggests the cultures in the area were still somewhat mobile when they built these massive monuments.

The lack of evidence for permanent residences—and early appearance of grand monuments—challenges the idea that monuments, kings, and agriculture all appeared in lockstep, Inomata says.

But some caution is needed in interpreting the lidar results, says Timothy Murtha, a landscape archeologist at the University of Florida. San Lorenzo itself may be an old site, but it went through several eras of development. He says more radiocarbon dating of the ceremonial structure will be needed to determine whether the platform itself really predates Aguada Fénix or was a later addition.

Still, the study is “remarkable and innovative,” Murtha says. “It’s a foundational approach that will set off a whole bunch of work.”

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