Archaeologists have rediscovered 143 more enormous drawings called geoglyphs etched on the rocky ground of Peru’s Nazca Desert, with one of the finds coming courtesy of a machine-learning algorithm. The new images emphasize how much ancient art lies on the 450 square kilometer (280 square mile) Nazca Desert and how much of it archaeologists still need to find and document. Masato Sakai, an archaeologist from Yamagata University in Japan, and his colleagues say mapping the Nazca Lines could yield clues about their purpose.

No, it’s not an alien

It’s almost poetic that the first Nazca geoglyph spotted by AI apparently depicts a human—or at least something that looks humanoid. The five-meter-long figure shows up very faintly in aerial photos; if you don’t know it’s there, you’d probably miss it. With a little digital image enhancement, though, the geoglyph is a solid figure in a tall headdress holding a stick. Two thousand years after the fact, archaeologists aren’t yet sure what the stick is for; it could be a weapon or something used in a ritual. For that matter, the figure could turn out to be a god or a spirit, rather than a person.

IBM’s Watson Machine Learning Community Edition learned what Nazca geoglyphs looked like by analyzing aerial photos of the ones archaeologists have already documented. Then Sakai and his colleagues handed the algorithm a massive set of high-resolution aerial photos of the desert floor. It searched for features—shapes, patterns of light and dark contrast, and others—that looked like those of the geoglyphs it had seen before. The algorithm pointed out several shapes that might be geoglyphs, and Sakai and his colleagues chose one—the person in the headdress—to investigate in person.

Aerial and satellite photos make it easier to search vast swaths of the desert for geoglyphs. But those images add up to a daunting mountain of data, and combing through that mountain is a slow process for humans. Sakai and his colleagues hope AI can speed up the process of mapping the Nazca Lines. Although the headdress-wearer is an impressive find, the future of AI in the Nazca Desert depends on how often the algorithm incorrectly identifies a site and how many real glyphs it misses. That’s information that Sakai and his colleagues haven’t shared yet. But this isn’t the first time that machine learning has been used in archaeology, so there’s good reason to be optimistic about its prospects.

Location, location, location

One hundred and forty-two more geoglyph discoveries are the product of many seasons of fieldwork and countless hours spent poring over aerial photos. They include enormous geometric designs, along with stylized alpacas or llamas, birds, cats, fish, foxes, monkeys, snakes, and humans. The largest stretches across 500 meters (330 feet) of desert, while the smallest covers just five meters (16 feet).

The new finds could help archaeologists figure out what at least some of the Nazca’s spectacular landscape-scale artwork was actually for. Between 1,000 and 2,000 years ago, the Nazca people created hundreds of shapes by scraping dark red pebbles away from the desert’s surface to expose the lighter soil beneath. The images of animals, plants, and geometric shapes each stretch dozens or hundreds of meters across the desert floor, and some require a bird’s-eye view to fully appreciate. Archaeologists knew about just 30 of these geoglyphs when the Nazca Lines became a UNESCO World Heritage Site in 1994, but since then, the number has risen to over 900.

Sakai and his colleagues suggest that some of the smaller figures, like the person in the headdress, may once have been signposts or travel markers. The headdress-wearer is part of a whole category of geoglyphs that tend to turn up along paths and on slopes, where passersby on foot can clearly see them from the right vantage point. Like the headdress-wearer, these geoglyphs are mostly animals and people, with solid, filled-in shapes instead of outlines, and they’re usually less than 50 meters (165 feet) long.

The larger geoglyphs, on the other hand, tend to be geometric designs or huge outlines of animals on the desert floor. Most of them are so big—up to 100 meters (330 feet) wide—that people on foot would have trouble seeing the entire shape all at once.

The ground inside and around several of the huge shapes is littered with ancient potsherds, dating between 100 BCE and 100 CE. Sakai and his colleagues suggest that the huge shapes on the ground may have marked places for rituals and gatherings.

To test that idea, Sakai and his colleagues need more information about how the geoglyphs are arranged on the desert landscape. For one thing, if the small, filled-in figures turn up in places that don’t make sense for travel markers, then the researchers will need to rethink that explanation. To get the information they need, the archaeologists plan to keep surveying the Nazca Desert on foot, mapping the ancient geoglyphs.

But they’ll also turn to another AI for help. Another IBM platform called PAIRS will use a decade’s worth of survey data to create a map of every known geoglyph on the Nazca Desert, then search for patterns in their distribution.

Mapping the geoglyphs may also help protect them in the long run. In order to preserve the geoglyphs, authorities first need to know where they all are and which ones are most at risk from vandalism and the growth of nearby cities.

Listing image by Sakai et al. 2019

https://arstechnica.com/?p=1626481