Strange prehistoric drawings found near dinosaur footprints in Brazil

A dashed line indicates petroglyphs made by indigenous people, while a continuous line shows theropod dinosaur footprints. (Leonardo Troiano via CNN Newsource)

Prehistoric humans in Brazil carved drawings in the rock next to dinosaur footprints, suggesting that they may have found them meaningful or interesting, a new study has found.

The rock carvings, which archaeologists call petroglyphs, are at a site called Serrote do Letreiro in Paraíba, an agricultural state on the eastern tip of Brazil. Researchers first observed the marks in 1975. But they are now interpreted as relating to the footprints following recent field surveys aided by drones, which uncovered previously unseen carvings. The tracks belong to dinosaurs from the Cretaceous Period, which ended 66 million years ago.

"People usually think that Indigenous people weren’t aware of their surroundings or didn’t have any kind of scientific spirit or curiosity," said study coauthor Leonardo Troiano, an archaeologist at the Institute of National Historic and Artistic Heritage in Brasilia. "But that’s not true. It’s very clear that they were interested in the footprints. We’ll never know if they knew about dinosaurs, but it is clear that they were curious about the prints and thought they were meaningful in some way."

The Serrote do Letreiro petroglyphs aren’t the first examples of rock art found close to dinosaur prints, but the authors of the study said they believe that the unprecedented clarity of the association between the two at this particular site could have significant implications across paleontology, archaeology and cultural heritage studies.

Geometric shapes

It’s unclear how long ago the petroglyphs were made. But the study — published in March in the journal Scientific Reports — notes that radiocarbon dating has found burial sites in the area to be between 9,400 and 2,620 years old, suggesting the tribes that left them must have lived during that time.

"These people were probably living in small communities, using natural rocky shelters that are very abundant in the area," Troiano said.

"This region in Brazil is like the Outback in Australia — it’s really hot and there’s no shade, so it’s not easy to stand there and carve the rock. It requires a lot of effort, so when they picked this location, they were being very intentional," he added. "They could have used so many other rock outcrops in the surroundings, but they chose this one."

The drawings are varied in style, suggesting multiple artists might have had a hand in them. Some have shapes reminiscent of plants, while others resemble geometric forms, including squares, rectangles and circles. The circles have crosses or lines inside them, which might look like stars, Troiano said. However, what these markings mean remains a mystery.

"They all seem to be abstract, and if they represented something to the people who made them, we don’t know what it is," he said.

The tracks at Serrote do Letreiro belong to three types of dinosaurs: theropods, sauropods and ornithopods. The researchers suspect that the people who carved the rock might have mistaken some of them for the footprints of rheas — large native birds similar to ostriches, which have tracks that look almost identical to those of theropod dinosaurs.

It’s harder to imagine what the prehistoric people could have thought of the sauropod prints, left by some of the largest herbivore dinosaurs that ever lived, and therefore unlike any animal that would have been familiar to them. Probably for this reason, an intentional association between the drawings and these particular prints is less clear, the study noted.

Dinosaur rituals

Troiano said he believes that the marks might have been left during communal gatherings.

"I think rock art creation was embedded in some sort of ritual context: people gathering and creating something, perhaps utilizing some psychotropics. We have a plant called jurema, which is hallucinogenic, and it’s still used to this day," he said. “We can speculate that people were using it in the past as well because it’s so abundant and common in the region. I think they were interested in what the footprints represent, and I suppose they identified them as footprints. They noticed it wasn’t random.”

There are other sites, Troiano said, with petroglyphs in the vicinity of dinosaur footprints — in the United States and Poland — but they are displaying “nowhere near the same level of intentionality,” he said. Intentionality is defined not only by how close the drawings are to the prints but also whether or not they overlap with them. If they don’t overlap, it suggests "thoughtfulness" by the makers, the study suggests.

Troiano added that he’s working on a follow-up paper that will go deeper into the interpretation and the analysis of the Serrote do Letreiro petroglyphs, building upon the findings of the current study.

The direct association of the drawings with dinosaur fossil tracks is unique and may shed more light on rock art importance, meaning and significance, according to Radosław Palonka, an associate professor of archaeology at the Jagiellonian University in Kraków, Poland, who has worked on similar petroglyphs but was not involved in the study.

“The fact that the locations of the rock art panels have been chosen specifically is shown by, among others, the fact that representatives of the communities that created rock paintings or petroglyphs often placed them very close to older images left by other cultures,” Palonka said via email. “This was the case in various parts of the world where rock art was practiced, and it is very clearly visible, among others, in the North American Southwest/U.S. Southwest, where my scientific interests are focusing.”

Jan Simek, a distinguished professor of anthropology at the University of Tennessee, Knoxville, agreed. “The paper provides an interesting new example of how ancient people observed and incorporated fossils on the landscape into their religious experiences and interpretations,” said Simek, who also was not involved with the new petroglyphs study.

“The (Stanford University) historian of science Adrienne Mayor has shown how ancient Greeks and Romans saw fossils as evidence of giants and monsters from their own mythologies and how indigenous North American peoples saw their origin narratives in the fossils they observed scattered across their landscapes,’ Simek said via email. “The Brazil case is another archaeological example of this very human tendency to tie the spiritual world created in the imagination to unexplained things in the world around us.”