Drawings scratched into a desert
The Nazca Lines are geoglyphs, from the Greek for “earth” and “carving”: images made on the ground itself, on the dry plains of southern Peru, about 400 km south of Lima. Their core area covers some 450 square kilometres. Most were made more than two thousand years ago by the people of the Nazca culture, and some are older still, the work of the earlier Paracas culture.
The technique was simple. The desert is covered with a layer of darker, weathered gravel; remove it, and the lighter ground beneath shows through. Piled along the edges, the removed stones frame each line. Because it almost never rains here and the wind sweeps sand out of the grooves, the drawings have survived for two millennia.
There are three kinds of drawing. Straight lines run for several kilometres across the plain, and geometric shapes, such as triangles, trapezoids and spirals, cover large areas. Then there are the figures: a monkey about 110 metres long, a killer whale of 65 metres, a hummingbird of 50, a spider of 46, a pelican of 285, as well as flowers, plants and humanlike beings. Some of the oldest, humanlike images resemble the earlier petroglyphs of the region.
How the AI found what people had missed
It took nearly a century to find 430 figurative geoglyphs. They come in two styles. The famous line-type figures, like the monkey and the hummingbird, are giant drawings made with a single line, on average 90 metres long, and only 50 of them are known. The other 380 were relief-type figures, made by clearing a patch of ground and piling the stones, on average only 9 metres in size and, after two thousand years of wind and sun, often very hard to see.
Searching 629 square kilometres of desert for faint figures 9 metres across, by eye, on aerial photographs, was hopelessly slow. So Masato Sakai of Yamagata University and a team from IBM Research trained an AI model to spot them, with only a few hundred known examples to learn from. The model flagged thousands of possible sites; archaeologists screened them and kept 1,309 promising candidates, on average one for every 36 suggestions.
Then came the walking. From September 2022 to February 2023, with the permission of Peru’s Ministry of Culture, the team checked the candidates on foot, in 1,440 hours of fieldwork. They confirmed 303 new figurative geoglyphs, all of the relief type, and 42 new geometric ones. Of the 303, 178 had been pointed out by the AI; most of the others belonged to new groups of figures found during the checks. The count of known figures rose from 430 to 733.
What the new figures show
With so many more examples, a pattern appeared. The relief-type figures mostly show people and things people had changed: 33.8% are humanlike figures, 32.9% are decapitated heads and 14.9% are domesticated llamas or alpacas. They lie on average 43 metres from the winding trails that cross the plain, close enough to be seen by someone walking past, so they were probably made and viewed by individuals or small groups.
The giant line-type figures are different. Most of them (64%) show wild animals, and they lie on average 34 metres from the great network of straight lines and trapezoids. That suggests they were made and used by whole communities, for rituals.
Why were they made? The debate goes on
The lines became widely known in the twentieth century, and theories followed quickly. In 1941 the American historian Paul Kosok flew over them and suggested they had astronomical purposes. The German translator María Reiche, who spent years studying the site and fighting for its protection, concluded that it was a huge astronomical calendar, with some animals modelled on groups of stars.
Did the stars explain it? Not as far as anyone has shown. In 1967 the American astrophysicist Gerald Hawkins found no correlation between the movements of the sky and the design of the lines, and the idea that the animals are constellations has been criticised as a Western way of reading the sky. Other explanations link the lines to water, to processions or to sacred paths: the international Nasca-Palpa Project, begun in 1997, found platforms at the end of many lines and, on one of them, fragments of thorny oyster shell (Spondylus), which suggest ceremonies connected with water.
No single theory has won. The 2024 survey leaves the mystery open too. What it adds is a distinction between two kinds of figure: small reliefs along everyday trails for a few people, giant figures along the ritual network for many.
Where to see them
The lines lie on the plains between the towns of Nazca and Palpa, in the Ica region of southern Peru. The large figures are best seen from the air. The Pan-American Highway crosses the protected area and has damaged some lines and figures, but most remain in fair condition.
Sources
- M. Sakai et al., “AI-accelerated Nazca survey nearly doubles the number of known figurative geoglyphs and sheds light on their purpose”, Proceedings of the National Academy of Sciences 121, no. 40 (2024).
- UNESCO World Heritage Centre, “Lines and Geoglyphs of Nasca and Palpa” (700).
- Encyclopaedia Britannica, “Nazca Lines” and “Nazca”.
