Secrets of ‘Leti’ hidden in the caves

The first partial skull of a Homo naledi child has been discovered from South Africa's Cradle of Humankind. A discovery unearthed deep within the area's Rising Star cave system, the fragments are believed to be from a four-six-year-old who died about 250,000 years ago.

Named “Leti” by researchers after the Setswana word ‘letimela’ meaning ‘the lost one’, the findings consist of 28 skull fragments and six teeth. When reconstructed they show the frontal orbits, and top of the skull with some dentition.

“Finding cranial material is such a rarity, even in this cave system,” says Tebogo Makhubela, a geologist from the University of Johannesburg (UJ) who has been working in the area since 2013.

“Right from the start we knew there was something different about the material we found. And a year and a half later, we confirmed the material as skull fragments from a Homo naledi child.”

The Rising Star cave system has yielded several important fossils finds, notably in its Dinaledi Chamber. It was here that researchers discovered the first ever evidence of Homo naledi, a new species of hominin, in 2013.

Makhubela has been part of the team since that time, first as a master’s student compiling petrographic analyses and geological mapping, and later contributing to evidence dating those early fossils to between 335,000 and 236,000 years ago.

Today, Makhubela is the second author on a paper shedding light on the unusual geology of where Leti’s skull fragments were discovered to suggest the  remains may have been deliberately deposited.

Makhubela is the only Black South African scientist on the paper, which also includes two other Black South African explorers Maropeng Ramalepa and Mathabela Tsikoane, from the Centre for the Exploration of the Deep Human Journey, at the University of the Witwatersrand.

“The opportunity to study the original context in which we find these fossils, the environment where they are discovered, is almost more important than the analytical and laboratory work I was doing when I joined the project,” he says.

Makhubela says understanding the depositional context is very important for understanding laboratory results, but more importantly the interpretation of how the fossils ended up inside the cave. “The petrography or age results alone cannot tell us that the skull fragments were deliberately deposited, which has serious implications for when such a cultural practice of deliberately disposing the dead started,” he says.

Indeed, Homo naledi is a human-like species that, according to dating of existing fossil evidence, lived in Africa at the same time as Homo sapiens. However, its physical features are more consistent with species discovered living 1.5m years earlier.

“It blows your mind,” says Makhubela. “To have this morphologically primitive species living 300-200,000 years ago when other hominins have been identified having more complex features shows evolution isn’t as simple or as clear as we thought it would be.”

With Leti’s discovery, researchers can get one step closer to understanding how Homo naledi developed and learning how it could have lived alongside and with Homo sapiens. Makhubela is excited about finding those answers.

“My journey has taken me from being a runner in the field to being in a position where I’m leading important fieldwork that can only be done by a few specialised people,” Makhubela says. “I’m really happy and proud that my hard work has been rewarded.”

That’s not to say there haven’t been challenges along the way. Makhubela says he has experienced moments of doubt and more than one instance where he was the first or the only person of colour.

“Someone has to be the first, that is what transformation is,” he says. “But we must remember that at some point, things will change.”

That moment may be on the horizon. Makhubela says he is watching the development of young, Black South African students who show great potential for the future of palaeoscience. “In the next few years, these are the scientists who I will be working with, and they won’t be the first or the only ones, they will be part of a team,” he says.