AI discovers hundreds of ancient Nazca drawings in Peruvian desert

Hundreds of ancient drawings depicting decapitated human heads and domesticated llamas have been discovered in the Peruvian desert with the help of artificial intelligence. Archaeologists have previously linked these creations to the people of the Nazca culture, who started etching such images, called geoglyphs, into the ground around 2000 years ago.

These geoglyphs are smaller and older than the Nazca lines and other figures found to date, which portray huge geometric shapes stretching several kilometres or wild animals about 90 metres long on average. The newly discovered images typically depict humanoid figures and domesticated animals around 9 metres long. Some even hint at human sacrifice, portraying decapitated heads and killer whales armed with blades.

“On some pottery from the Nazca period, there are scenes depicting orcas with knives cutting off human heads,” says Masato Sakai at Yamagata University in Japan. “So we can position orcas as beings that carry out human sacrifice.”

Sakai and his colleagues found the smaller geoglyphs by training an AI model to look for them in aerial photos. The high-resolution photos covered an area about 10 times as large as Manhattan, which encompassed the desert plateau called the Nazca Pampa and its surroundings, located on the UNESCO World Heritage Site for the Nazca lines. The AI then produced a gridded map that categorised the probability of each grid square containing geoglyphs.

Researchers still spent more than 2600 hours manually inspecting the highest-probability photos and doing field inspections at the sites. But they estimate the AI helped speed up the screening process by a factor of 50 “by eliminating 98 per cent of low-probability aerial imagery from consideration and providing probabilities for the remaining 2 per cent”, says co-author Marcus Freitag at IBM Research in New York.

The researchers followed up on the AI suggestions and discovered a total of 303 figurative geoglyphs during field surveys in 2022 and 2023. Of these figures, 178 geoglyphs were individually identified by the AI. Another 66 were not directly pinpointed, but the researchers found them within a group of geoglyphs the AI had highlighted.

“The AI-based analysis of remote sensing data is a major step forward, since a complete map of the geoglyphs of the Nazca region is still not available,” says Karsten Lambers at Leiden University in the Netherlands. But he also cautioned that “even this new, powerful technology is more likely to find the better visible geoglyphs – the low hanging fruits – than the more difficult ones that are likely still out there”.

Nearly 1000 AI-identified candidates still await inspection during future field surveys, says Sakai. Such smaller geoglyphs generally appear on hillsides near winding trails and probably featured in the “ritual activities of individuals or small groups”. In contrast, the huge line geoglyphs were more likely to be the focus of community-wide rituals, he says.

The AI screening process also offers hope for discovering geoglyphs in the broader region beyond the Nazca lines World Heritage Site, says David Beresford-Jones at the University of Cambridge. Speed is crucial because many geoglyphs “lie on the cusp of erasure through agricultural expansion, urban development and wind-power generation”, he says.