Lasers reveal 15th-century fortified Zapotec city in Mexico

Lasers shot from an aircraft have revealed the remains of a 600-year-old Zapotec city in southern Mexico, a new study finds.

The technique, known as lidar (light detection and ranging), works by having a machine aboard an aircraft send millions of laser pulses toward the ground and then calculating how long it takes for the lasers to bounce back. With this information, scientists can map the topography of the land.

To learn more about a 15th-century city known as Guiengola, a team led by Pedro Guillermo Ramón Celis, a post-doctoral fellow at McGill University in Canada, used lidar to map out the site in December 2022. The results were published by Celis on Nov. 8, 2024, in the journal Ancient Mesoamerica.

The Zapotecs are an Indigenous people that continue to thrive in Mexico. In the 14th and 15th centuries, some of the Zapotec migrated to the southern Isthmus of Tehuantepec, where they established Guiengola close to the Pacific Ocean. Although its existence was mentioned in historic Spanish texts and archaeologists have conducted work at the site, the city's full extent was not known until scientists used lidar to map it.

They found that "it covered 360 hectares [890 acres], with over 1,100 buildings, four kilometres [2.5 miles] of walls, a network of internal roads and a clearly organized urban layout with temples and communal spaces such as ballcourts, and the elites and commoners lived in separate neighbourhoods," according to a statement describing the research. There is a river that runs near the city.

They also identified a complex that measures about 148 feet (45 meters) from east to west and 164 feet (50 m) from north to south. "I propose that this complex was the residence and seat of power of Guiengola," Celis wrote in the journal article.

It appears that the site was inhabited for about 150 years, between roughly 1350 and 1500, and "was abandoned a few decades before European contact in 1521," Celis told Live Science in an email.

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An uncropped version of the lidar image that shows a complex where the city's rulers may have lived and ruled from.

The "South Palace Complex," as archaeologists call it, appears to have been a residence for elite individuals.

In the city's heyday, it likely had thousands of inhabitants. "I would say that at least 5,000 people were living permanently on the site," he noted.

At the time the city was founded, the Zapotecs were gradually conquering the region. After the conquest was complete, "it was no longer necessary to inhabit the mountains, and they moved 20 km [12.4 miles] south to where the modern town of Tehuantepec is located," Celis said.

Spanish records claim that the Aztecs attacked Guiengola in 1497 but were defeated by the Zapotecs. Celis found archaeological remains that may be from that campaign.

"In the most fortified sectors of the site, which are closest to the river, we have detected what could be accumulations of round pebbles and small river rocks by the thousands," Celis said, noting that they could be from the battle. The Aztecs, among other groups, used stones that were hurled with slings in warfare.

Celis plans to conduct more detailed archaeological research in that area later this year.