(CNN) – A group of archaeologists working in Peru discovered, with the help of artificial intelligence, 303 previously unknown giant symbols carved in the Nazca desert.
The engravings include birds, plants, spiders, human figures with headdresses, decapitated heads and an orca wielding a knife.
Described in a study published Monday in the PNAS magazinethe discovery almost doubles the number of Nazca geoglyphs known, mysterious works of art formed in the ground by moving stones or gravel dating back about 2,000 years. The researchers’ findings also shed some light on the enigmatic purpose of the symbols.
Located 50 kilometers (31 miles) inland from the southern coast of Peru, the enormous symbols were found in the desert in the early 20th century. About 500 meters (1,640 ft) above sea level, the geoglyphs have survived the centuries because the dry desert region is sparsely populated, unaffected by floods, and unsuitable for cultivation.
The rate of new finds has increased in recent years due to the use of high-resolution remote imaging, with an average of 19 geoglyphs found annually between 2000 and 2020, according to the research. However, the use of artificial intelligence to narrow down the pool of potential candidates has accelerated the pace and, more broadly, promises “a revolution in archaeological discoveries,” according to the study.
A group of researchers led by Masato Sakai, a professor of archeology at Yamagata University in Japan, made the latest discovery of geoglyphs by training an object detection artificial intelligence model with high-resolution images of the 430 Nazca symbols mapped in 2020. The team included researchers from IBM’s Thomas J. Watson Research Center in Yorktown Heights, New York.
Their main challenge was the limited number of images. These models are typically trained using tens of thousands of images, according to the study.
The team decided to focus on the smaller, more figurative symbols of the two types discovered in the desert. Figurative geoglyphs are typically about 9 meters (30 feet) in length and have been more difficult to identify than the larger linear types, which are 90 meters (98 yards) in length and have therefore been detected more easily during aerial reconnaissance.
The AI model was not perfect at all. It suggested more than 47,000 potential sites in the desert region, which covers 629 square kilometers (243 square miles).
The team examined and ranked those suggestions, identifying 1,309 “high potential” candidate sites. For every 36 suggestions made by the AI model, the researchers identified “one promising candidate.”
However, the study authors noted that the use of AI was a game-changer in terms of reducing the amount of work needed to narrow the search. It allowed “the focus to shift to valuable and specific fieldwork in the Nazca Pampa,” according to the study.
Between September 2022 and February 2023, the team tested the accuracy of their model in the Nazca Desert, surveying promising sites on foot and with the use of drones, and finally “field-verifying” 303 figurative geoglyphs.
“Geoglyphs in good condition were immediately recognized for what they were,” Sakai said in an email. “In the case of those that are in poor condition, we are investigating what they are through detailed field work.”
Of the 303 newly discovered figurative geoglyphs, 178 were suggested by the model and 125 were additional finds. Of these, 66 were found as part of a group of geoglyphs discovered by artificial intelligence, while 59 were discovered during field work without any help from AI.
There may be many more geoglyphs waiting to be discovered.
The team was unable to screen 968 of the promising candidates during the field season detailed in the research. Given the initial success rate of field work based on the AI model, at least 248 additional figurative geoglyphs could be discovered, according to one study estimate.
It is “incredible” to have doubled the number of known geoglyphs, especially considering the limited training data, said Amina Jambajantsan, a researcher and data scientist at the Department of Archeology at the Max Planck Institute for Geoanthropology in Jena, Germany. Jambajantsan was not involved in the Nazca research, but uses an AI model to identify burial mounds in Mongolia based on satellite images.
His own work often followed a similar pattern to the Nazca team, he said, with AI-based suggestions often leading to additional discoveries on the ground during field work. “Artificial intelligence is great, but you still need humans,” he said.
AI has the potential to make enormous contributions to archaeology, although the models are not yet perfectly accurate, he said.
“The problem is that archaeologists don’t know how to build a machine learning model and data scientists are usually not really interested in archeology because they can make a lot more money elsewhere,” Jambajantsan added.
Deciphering the purpose of the Nazca symbols
It is not clear why the Nazca people created the symbols. The main hypothesis is that they formed a sacred space that was perhaps a place of pilgrimage. Other theories propose that they had a role in calendars, astronomy, irrigation or in movement, such as running or dancing, or in communication, the study noted.
An analysis of the newly discovered symbols, along with those already known, revealed some interesting trends, Sakai said.
Larger, linear-type geoglyphs, easily visible from above, generally depict wildlife, such as animals or plants, while smaller, relief-type geoglyphs include humans or things involving humans, such as human sacrifice or domesticated llamas.
The study also revealed more clearly a network of roads in the desert, many of which were near different groups of symbols.
The smaller geoglyphs were found along ancient winding paths likely made across the desert by the Nazca people who viewed the symbols in small groups, according to the study. The largest Nazca symbols were near networks of straight lines, squares and trapezoids etched into the earth.
These symbols, according to the study, were probably used for ceremonial activities, perhaps at the end of a pilgrimage, and could be considered planned public architecture.
Sakai said work was underway to decipher the precise meaning of the geoglyphs and their mysterious purpose, which researchers hope to publish in the future.
“Our findings suggest that their meaning is formed through their combinations,” he said, referring to the way the Nazca geoglyphs are grouped.
