Since its initial discovery was announced in 2015, an extinct hominid species named Homo naledi (H. naledi) has been making anthropological waves. Now, three new preprint studies published June 5 in the journal eLife and presented at the Richard Leakey Memorial Conference suggest that these human cousins may have buried their dead and carved symbols into cave walls, showing that they were capable of complex behavior despite their smaller brains.
While the research hasn’t been peer-reviewed yet, some outside scientists believe that more evidence is needed to challenge what is already known about how complex thinking evolved in humans. If these new findings are true, it would overthrow the current belief that humans are the only species to bury their dead.
H. naledi’s brain is roughly one-third the size of the human brain. Previously, most scientists believed that the mental capacity behind burial, making marks, and other more complex cultural behaviors required a bigger brain, like those of the Neanderthals and Homo sapiens.
“It’s not how big your brain is, it’s how you use it and what it’s structured for,” study co-author and University of Wisconsin-Madison anthropologist John Hawks said in a statement. Hawks has helped lead the H. naledi team since its beginning.
The fossil remains of the species were first uncovered about 10 years ago in the Rising Star cave system northwest of Johannesburg, South Africa. Since then, team members have descended into the tight underground caves that they say show this species in a new light.
One study describes the potential intentional burial sites that held fossilized remains of children and adults in the fetal position and buried in shallow holes in the ground. One of the other studies describes a series of marks carved into the cave’s limestone walls that include cross-hatched lines, squares, and triangles.
Additionally, H. naledi had a smaller frame based on the skeletons that have been excavated. Archaeologists estimate that the average individual weighed less than 90 pounds and was under five feet tall. This small stature would have helped them navigate the extremely narrow and cramped passageways in this cave system. Some of the cave system’s labyrinth of passages are as narrow as seven inches and are located 300 feet underground.
The bones found in the cave are between 236,000 and 335,000 years old, which is older than the graves at Qafzeh cave in Israel. These 92,000-year-old graves are commonly cited as the earliest known examples of human burial.
“This is a great moment in human history,” Lee Berger, the South African paleontologist and National Geographic explorer-in-residence who co-wrote all three papers, told The Washington Post. Berger said people have wondered, “‘What will we do when we meet another culture as complex as us?’ Well, you just did.”
Berger has drawn criticism in his three-decades-long career for announcing or publishing research before gathering sufficient supporting evidence. He, in turn, has criticized the practice of waiting years to share discoveries with the public, calling it “elitist,” according to The Washington Post.
These new findings show that the caves still have more to offer scientists working to understand human evolution, according to Hawks. The team hopes to have more trained eyes and experts into the caves to search for more evidence.
“We have to approach it like an escape room. We have to study every hidden detail now,” Hawks says. “This whole cave system might be part of some kind of cultural space.”