'Massive evidence' on evolution: Extinct human species with tiny brains 'used fire' to live underground

Researchers claim to have discovered new evidence of extinct human species who lived in the underground caves of modern-day South Africa.

The archeological findings reveal that Homo naledi, a prehistoric human species used fires to prepare food and navigate in the darkness of underground caves, according to South African paleoanthropologist and National Geographic explorer Lee Berger. 

"We have massive evidence. It's everywhere," said Berger, who reported the findings in a press release and a Carnegie Science lecture at the Martin Luther King Jr. Memorial Library in Washington last week.

"Huge lumps of charcoal, thousands of burned bones, giant hearths, and baked clay" were discovered.

Despite brains one-third the size of humans, the new findings on the primitive species with a chimpanzee-like skull may fundamentally alter how we think about complex behaviors. 

Such conduct was previously believed to only be found in large-brained creatures like modern humans and Neanderthals.

Homo naledi lived approximately 230,000 years ago, averaging 144 centimeters in height and 40 kilograms in weight, according to the new findings. 

With ape-like shoulders, a tiny brain that was a little larger than a chimpanzee's, and teeth, it had an odd blend of primitive and contemporary traits.

"We are probably looking at the culture of another species," Berger told Washington Post (WP) in an interview. 

"There are a series of major discoveries coming out over the next month," said Berger.

Mystery of navigating dark narrow underground passes 

The species' movements through the maze-like network of underground tubes at Rising Star, which are completely dark and require intricate maneuvers through openings in the rock only 17.5 centimeters wide, remain a mystery.

Due to the narrow passes, only 47 persons, all of whom were little and thinly built, had been able to enter the Dinaledi chamber, where the first Homo naledi fossils were found in the last decade.

Berger, who is 188 cm tall, decided to take a chance and enter the labyrinth in August of this year after reducing 25 kg of weight.

"It's not a space made for six-feet-two people like me. I'm by far the largest person who's even been in," he said. 

Aware of the possibility of him getting stuck, he took the risk. "I almost died on the way out," Berger admitted. 

Berger noticed that the granite in the Dinaledi chamber had some darkened spots and soot flecks when he glanced up.

"The entire roof of the chamber is burnt and blackened," he said.

Keneiloe Molopyane, a colleague of Berger's at the University of the Witwatersrand, discovered a huge hearth next to a smaller hearth with burned antelope bones 15 cm below the cave floor at the same time while Berger was still analyzing the ashes.

Berger also discovered a tower of burned rocks with a base of ash and burnt bones in a location known as the Lesedi chamber.

"Body disposal in one space and cooking of animals in adjacent spaces" Homo naledi also seem to have used the space in exciting ways, said Berger. 

"The capacity to make and use fire finally shows us how Homo naledi ventured so deep into dangerous spaces, and explains how they may have moved their dead kin into such spaces, something likely impossible without light. It also hints at a complex naledi culture becoming visible to us." added Berger, who has allegedly disregarded scientific tradition by not reporting the findings first in a peer-reviewed journal. 

Non-peer-reviewed findings - the controversy

The unpublished discovery and new details on humans' evolution have sparked both enthusiasm and skepticism in the scientific community.

The choice to publicize the fire discovery in a seminar on December 1 before the formal scientific investigation was published has proven contentious because the dating of the charred bones is still being done.

"It's impossible to evaluate Lee Berger's claims properly without seeing the full evidence, but apparently that is forthcoming," Chris Stringer at the Natural History Museum in London told New Scientist. 

"With all due respect to Lee and his teams for a series of great finds, this is not the way to conduct science or progress scientific debate about potentially very important discoveries."

The discovery, however, may have provided Francesco d'Errico from the University of Bordeaux in France with information about how they (Homo naledi) handled their dead and how their society was structured.

"If Homo naledi were shown to have mastered fire and used it to gain access to the most remote areas of the Rising Star karst system, this could have very important implications for the interpretation of mortuary practices conducted at the site," he said.

"The control of an artificial light source allows the organization of actions in space and time and, in the case of mortuary practices, facilitates the participation of several members of the group in collaborative and shared actions."

Significance of the discovery

The significance of the fire-use revelation is much more profound, according to Berger. 

If these small-brained, largely ape-like humans were capable of the sophisticated thought processes necessary to create and manage fire, then "we're beginning to see the emergence of a cultural pathway and behavior that we thought, until this moment, was the domain of [Homo sapiens and Neanderthals]," he said.

In 2013, two cave divers in South Africa's Rising Star cave system made the first known discovery of Homo naledi when they entered a previously undiscovered chamber through an extremely narrow route. 

They found thousands of fossilized bones scattered on the ground, which later led to Homo naledi being classified as a new species in 2015. 

However, the dating of its fossil remains in 2017 revealed that it lived relatively recently, between 230,000 and 330,00 years ago. This suggests that it may have coexisted alongside Homo sapiens, which emerged in Africa around 300,000 years ago.

And many scientists who previously thought a small-brained hominid couldn't manufacture and use fire inside a cave system may reevaluate their beliefs in light of the most recent "remarkable discovery."