Straight lines, geometric patterns and gigantic animal figures – the Nazca Lines in the highlands of Peru are among the most enigmatic testimonies of past cultures. But many more of these geoglyphs are still waiting to be discovered. Archaeologists have now used artificial intelligence to track down even more Nazca geoglyphs in the Peruvian pampas. Of the candidates identified by the AI system in aerial photographs, 303 actually turned out to be new, figurative Nazca geoglyphs during on-site inspections. These geoglyphs, which are on average just under ten meters in size, almost double the number of known figurative Nazca geoglyphs. They also enabled the team to find out more about the motifs and their possible function.
The Nazca lines in the highlands of Peru are world famous – and still mysterious because of their monumental size. The more than a thousand known geoglyphs were created between 2100 and 500 years ago by members of the Nazca culture, who dug these motifs, some of which were several kilometers long, into the stony desert floor. Some of these geoglyphs consist of abstract geometric shapes and lines, others show figures, including images of birds, spiders, cats or monkeys. “The Nazca geoglyphs offer archaeologists a unique window into the culture and beliefs of the peoples who made these geoglyphs at least 2000 years ago,” explain Masato Sakai from Yamagata University and his colleagues. What these sometimes gigantic geoglyphs were used for, however, is still disputed today. Some archaeologists suspect that the abstract lines in particular were aligned according to astronomical reference points and had a calendar function. The figurative representations may have served ritual purposes, but may also simply have been art. Many of the smaller figure reliefs are located on slopes, making them visible from afar.
303 new figure representations identified
Interpreting the Nazca geoglyphs is also difficult because only a fraction of them have probably been discovered so far. Many of the smaller images are barely recognizable even in aerial photographs because the lines have faded over the centuries. The area over which these images of the earth are spread is also huge: “The Nazca Pampa and the surrounding potentially interesting areas cover more than 629 square kilometers,” write Sakai and his colleagues. “It took almost a century to discover 430 figurative Nazca geoglyphs there.” To track down more of these geoglyphs, the researchers have now used artificial intelligence. They used a neural network pre-trained to evaluate aerial photographs and trained it to recognize the typical lines in the desert floor using sections of Nazca geoglyphs. The team concentrated its search on the smaller, only up to ten meters tall, figure motifs of the so-called relief type geoglyphs.
The AI-supported search was successful: The neural network identified 1,309 particularly promising candidates for as yet unknown earth images in the Peruvian Nazca plateau. The archaeologists then checked these candidates on site: Between September 2022 and February 2023, they visited the locations where the AI had tracked down potential Nazca figures. With success: “We found 303 new figurative relief geoglyphs, almost doubling the number of previously known geoglyphs of this type,” report Sakai and his team. In addition, the AI also discovered 42 new geometric earth images. During their field expeditions, the archaeologists did not manage to check all of the candidates on site – 968 remained unchecked. Based on their previous false positive rate, they therefore assume that at least 248 more figurative geoglyphs will be confirmed during future visits.
Primarily human-related motives
The newly discovered Nazca geoglyphs offered the team new opportunities to analyze the motifs of the figurative earth images in more detail. In doing so, they discovered clear differences between the large line-type representations and the smaller relief-type figures. “The line-type geoglyphs mainly show natural motifs such as wild animals and plants,” report Sakai and his colleagues. “In contrast, 81.6 percent of the relief-type geoglyphs depict human figures, as well as motifs that are closely related to humans.” Of the latter, 33.8 percent are humanoid figures, 32.9 percent are heads without bodies, and 14.9 percent are depictions of domesticated camel relatives such as llamas and alpacas. Wild animals, on the other hand, only appear in just under seven percent of the smaller relief-type geoglyphs. Another difference was seen in the location of the earth images: the larger line-type figures are located in a more limited area and are closely linked to the large abstract earth images. The smaller Nazca geoglyphs, on the other hand, are spread over a large area and are often located close to informal paths.
According to the archaeologists, this suggests that the various Nazca geoglyphs also had different functions in the religious life and culture of the Nazca. “It is very likely that rituals were performed on the huge line-type geoglyphs, possibly at the beginning or end of a pilgrimage through the Nazca Pampa,” explain Sakai and his colleagues. The abstract lines and large figures were walked on as part of ceremonies. The smaller, more widely distributed figure images, on the other hand, were created by smaller Nazca groups and were primarily made for viewing. This is why they were often located on slopes and near the Nazca’s informal hiking routes – and showed human-related motifs, as the team explains. “Repeatedly viewing these relief-type geoglyphs from the trails probably made it easier to share information about human activities,” the researchers speculate.
Source: Masato Sakai (Yamagata University, Japan) et al., Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2407652121