A faded decades-old black-and-white photograph was the only lead Johny Isla had when he set out on the trail of a sea monster. The Peruvian archaeologist spotted the image at a 2014 exhibition in Germany about the Nazca Lines, the vast and intricate desert images which attract tens of thousands of tourists every year. The photograph taken in the early 1970s showed a mysterious killer whale deity carved in an arid hillside. The figure bore some resemblance to others he knew but he had never seen this one before. Isla, now Peru’s chief archaeologist for the lines, spent hours poring through archives, before returning to Peru – armed with a drone and a lifetime of local field experience – to find it. After several false starts, it took just two weeks to find the 25-by-65-metre image which had been hiding in plain sight in the hills of Palpa, about 30 miles north of Nazca, in a huge expanse of desert in southern Peru. The design carved into the hillside depicts a terrifying mythological beast, part orca but with a human arm holding a trophy head and several more heads inside its body. New research with drones has helped uncover hundreds of such figures carved in the desert near the lines in Nazca but which predate them by as much as 1,500 years. The archaeologists leading the effort now believe that the anthropomorphic orca figure fills in a missing link between hundreds of older geoglyphs and the Nazca culture’s desert etchings. The smaller forms were etched on hillsides in nearby Palpa by the Paracas and Topará cultures between 500BC and AD200. “This orca was made at a time of abundance and population growth in a moment of change from one society to another,” said Isla. Isla believe that the Topará crafted the orca figure during a period of dynamic transition. “The Nazca Lines are the culmination of a process of experimentation and improvement in technique which follow on from these older geoglyphs,” said Isla. Dating from AD200-700, the lines were given Unesco World Heritage status in 1994. More than a thousand of them – vast geometric patterns, and zoomorphic figures such as the monkey, the hummingbird and the whale – stretch across more than 400 sq km of the Nazca plateau. They were created by removing the top layer of pebbles to reveal the lighter-coloured material beneath. The newly discovered geoglyphs’ location on hillsides, however, marks a key difference, said Luis Jaime Castillo, a Peruvian archaeologist working on the Nazca-Palpa project with Isla. “Placing these geoglyphs on the slopes means that, in contrast with the Nazca Lines, you can see them if you are standing in the valley below where life and agriculture is taking place,” he said. “If the Nazca Lines were made by humans for the gods, these figures were made by humans for humans,” explained Castillo, a former minister of culture for Peru. “They are clearly representations of identifiable people. They are demarcating territories.” By contrast, the larger and more sophisticated geoglyphs further south in Nazca can not be viewed completely from the ground. According to Isla, the latest research indicates the Nazca Lines were “made with the purpose of asking the Gods for water and fertility in this desert area”. But archaeologists are still trying to understand the transition between the Paracas culture’s depiction of largely human figures intended to be viewed by other people to the Nazca iconography in which humans are all but absent. As the society grew larger the images may have been appropriated by the elite and given a sacred status, Castillo believes. It was a transition from drawings made by households or villages to grand designs made by an organisation closer to a state, he argues. On one hillside, a warrior wearing a headdress and carrying a staff or spear stands close to a female figure. Between them is a mythological creature with a mass of tentacles or snakes. The figures are believed to symbolise fertility. From the ground, the designs are now hard to see. But the drone’s eagle-eye reveals the full design on a monitor viewed by Castillo, who has long promoted aerial mapping techniques to register Peru’s estimated 100,000 archaeological sites, of which only a fraction have been excavated. Drones are being used not just to find geoglyphs but to “cover kilometres and kilometres and take thousands and thousands of pictures, which are then processed in very large computers”, Castillo said. “The images are so detailed that we can see a stone half an inch across.” The result of the process, known as photogrammetry, is highly detailed three-dimensional mapping of large areas, which in the case of the Nazca and Palpa Lines is a huge boost for their protection. The funding to discover these new geoglyphs came, ironically, as a result of an international scandal, when Greenpeace activists left damaging footprints next to the famous hummingbird, during a publicity stunt aimed at the 2014 UN climate change summit in Lima. Outrage over the incident prompted the US to give Peru a grant which helped fund Isla and his team. Registering and geo-referencing the geoglyphs is the best way to protect them from the spread of agriculture or urban encroachment, Castillo says. But just a few of the sites will be made known to the public so as not to make them a target for vandalism. Many of the hillsides, cut through by the Pan-American highway, are already covered with modern-day etchings ranging from brands of fertilizer to graffiti tags. Castillo believes that in the Nazca and Palpa area – already described by Unesco as having the “most outstanding group of geoglyphs anywhere in the world” – new discoveries may yet outnumber older ones. While the team have discovered hundreds of geoglyphs in Palpa, Castillo expects to find many more. “We’ve registered maybe just 5% of what there is,” he says.