A trained AI model scanned aerial photos of the entire Nazca Pampa region and surrounding deserts, ~50 km inland on the southern coast of Peru, nearly doubling the number of previously known geoglyph artifacts in only six months. Once AI tagged a potential geoglyph, archaeologists spent over 2,600 hours in the field inspecting, mapping, and using drone photography to validate the geoglyph as a discovery. This method of AI-assisted aerial survey and object detection, published September 23, 2024 in the Proceedings of the National Academy of Sciences, allowed the research team to be much more efficient and selective in how and where they spent their man-hours. It has taken a century for scientists to catalog the 430 known figurative glyphs in the region. It took this AI-assisted project six months to verify 330, with many more promising leads in the area that have yet to be archaeologically validated with a site visit.
Because of the large addition to the geoglyph database, the researchers team made new deductions about the context, meaning, and purpose of the different drawings and glyph types and their relationship to other known line drawings. These smaller relief-type glyphs were likely built by individuals or local communities to communicate with travelers or record aspects of Nazca life. These works of art were found close to the known walking trails and are mostly composed of human-related depictions like livestock, llamas, fish, birds, ceremonies, and also orcas wielding weapons. In contrast, the large scale Nazca lines and the associated geometric polygons, and larger-scale figure depictions were more likely built to facilitate larger regional gatherings, funneling travelers toward large gathering sites. Although the findings point to spiritual ceremony and cultural record as the main purposes of the creations, a complete map of the glyphs has yet to be obtained and the true meaning behind them may never be known.
The major challenges that the researchers faced included a limited number of existing geoglyphs that could be used to train the AI model to find other geoglyphs, and the difficulty in detecting the faint lines through visual inspection, where the landscape drwaings were usually partially obscured, weathered over time, and located in low-contrast land imagery.
What images are depicted in the landscape artwork?
Nazca Pampa is an extremely arid environment, experiencing only 4 mm of rainfall each year. This climate preserves the rocky, three-dimensional glyphs that decorate the pebbly landscape. The Nazca and antecedent Paracas cultures created four types of geoglyphs dating back to the 2000 B.C. The iconic Nazca Lines are linear geoglyphs that were created by manipulating the rocks and gravel to create straight lines running for several kilometers in some cases. Geometric polygons are another group of glyphs that include trapezoids, triangles, and other shapes. Figurative drawing occurred by two methods – line drawing and relief-style. The 50 identified line-style glyphs are largely represented by wild animal motifs that are almost a football field in length on average. A hummingbird, spider, killer whale, fox, monkey and others have been identified. These are often found near or in relation to the lines and polygons and may be associated with pilgrimages, ceremonies associated with the solstices, larger trade routes, or regional gatherings. They have also been correlated to subterranean water sources, like the underground aqueducts built by the industrious and inventive Paracas civilization.
The 380 relief-style glyphs are smaller, nine meters in length on average, and were found situated on slopes or hillsides. The drawings include human-related subject matter like humans, human heads, domesticated animals, plants, and wild animals. This study enabled researchers to link the distribution of the relief-style figurative landscape carvings and the network of walking trails used by the Nazca people. Archeologists now hypothesize that these were meant for viewing perhaps communicating the local tradition or lore. The drawing could also be the artistic expression of an individual.
How did AI identify so many new drawings?
Researchers deployed an AI model that was pre-trained on natural photographs and then tweaked the object-detection focus to produce a geoglyph probability map at 5-meter resolution. This approach allowed scientists to use cropped segments of existing large glyph photos to greatly increase the number of training glyphs for the model. For examples, instead of one large photo of a hummingbird, the photo was cropped into many pieces, containing only seemingly abstract parts of the line drawing. Each cropped piece could be used individually as a training photo, enabling the object recognition and probability map to more accurately identify faint lines in the rocky landscape that might coalesce into a new geoglyph.
Interestingly, AI did miss some, especially when there were many previously unidentified geoglyphs clustered within 50 m of each other. AI would find one or more of these, but not all of them. It did, however, draw human attention to the area and the researchers could fill in the area that was overlooked by the model, adding to the total of newly discovered artifacts. This was truly a collaborative discovery where credit is shared between human and machine.
The work is not done yet. Out of 968 additional tagged ‘promising candidates,’ the research team expects to add 248 figure-drawing relief-type geoglyphs to the Nazca Pampa UNESCO map in the coming years.
