Laser mapping shows the surprising complexity of the Maya civilization

A laser-shooting eye in the sky has revealed the previously unappreciated size and complexity of ancient Maya civilization, both before and during its presumed heyday, scientists say.

Maya people in what’s now northern Guatemala built surprisingly extensive defensive structures and roads as part of political systems featuring interconnected cities, starting at least several hundred years before the rise of Classic Maya society, an international team reports in the Sept. 28 Science. Classic Maya sites date to between around 250 and 900.

Aerial laser maps of northern Guatemala obtained in 2016 and map-guided ground surveys and excavations in 2017 compel a reevaluation of traditional assumptions about the ancient Maya, the team concludes. A long-standing idea that Classic Maya civilization, which covered parts of southern Mexico and much of Central America, once contained relatively small city-states ruled by warring kings has drawn increasing skepticism over the last decade (SN Online: 4/17/18). Laser technology shot down that scenario by gazing through forests and vegetation at 10 Maya sites — as well as in two areas with signs of Maya-era activity but no named sites — dating from a couple hundred years before the start of the Classic period to near its end. “Every Maya city was bigger and more populated than we previously thought,” says archaeologist Francisco Estrada-Belli of Tulane University in New Orleans. Estrada-Belli led the investigation along with archaeologists Marcello Canuto, also at Tulane, and Thomas Garrison of Ithaca College in New York.

A small plane carrying light detection and ranging equipment, or lidar, emitted laser pulses that gathered data on the ground’s shape across 2,144 square kilometers of northern Guatemala. Based on the more than 60,000 lidar-identified structures, the researchers estimate that a minimum of 7 million to 11 million people inhabited northern Guatemala near the end of the Classic Maya period.

Lidar views of the ancient Maya’s urban and rural infrastructure are particularly impressive, Estrada-Belli says. Water control was crucial. Much of the unsettled wetlands throughout northern Guatemala contain remnants of crisscrossing drainage channels that form grids within what must have once been agricultural fields. Some channels extend for one kilometer or more. Remains of stone terraces and low walls enclose many cultivation areas.

Drainage channels and terraces controlled water flow and eased soil erosion in heavily cultivated fields. “The ancient Maya were good stewards of their environment,” Estrada-Belli says.

Evidence of carefully irrigated agricultural fields challenges a popular view that Classic-era centers relied on food from soil-damaging, slash-and-burn farming. That practice eventually contributed to Maya civilization’s downfall, some researchers have argued.

Although sustainable cultivation techniques appear to have been standard for the ancient Maya, farmland near the largest Maya cities would not have provided enough food for local populations, the researchers say. Additional food was imported from distant sites belonging to common political networks, the team suspects.

Laser maps show that Maya cities varied substantially in population density and typically included less crowded zones in between city centers and rural areas. Most sites had a surprising number of defensive structures, Estrada-Belli says. Strategically placed bridges, ditches, ramparts, stone walls and terraces suggest military conflicts occurred frequently.

That didn’t stop cities from maintaining long-distance contacts and forming networks of politically aligned sites. Raised roads, or causeways, connected the earliest Maya sites, including three dating to a few hundred years before the Classic period, to nearby centers. These 10- to 20-meter-wide causeways run for as many as 22 kilometers. Later Maya cities primarily contain short causeways that served as entrances to public and ritual areas.

The new study builds on previous, smaller-scale lidar studies in and around Caracol, a Classic Maya city in western Belize (SN: 5/14/16, p. 22). Archaeologists Arlen and Diane Chase of the University of Nevada, Las Vegas directed that research.

“The new lidar data show that interconnected Maya cities go back to at least 300 B.C.,” Arlen Chase says.

Further lidar-guided surveys and excavations are planned, Estrada-Belli says. Some newly identified causeways extend beyond the edges of lidar maps, a sign that Guatemala’s forests hold further Maya revelations, he adds.