Fossil discovery of new species of human relative fans excitement, controversy

The discovery of 1,550 fossil fragments of a new species of human relative in a South African cave is fanning international excitement and some scientific controversy, with every bone of the species, Homo naledi, included in the find, along with the partial remains of at least 15 individuals.

H. naledi adults on average were shorter than 5 feet with long legs and tree-climbing and tool-using skills. A research team based at the University of Witwatersrand (Wits University) even suggested that H. naledi likely disposed of its dead ritualistically because the fossils were found in a remote chamber in the cave, known as Rising Star, 30 miles northwest of Johannesburg.

The discovery also required some scientific derring-do. Small female cavers were recruited to squeeze through a 7-inch crevice to gain access to the cave’s Dinaledi chamber 100 meters underground, where the remains had lain hidden for millions of years.

“This is a tremendously significant find,” stated Terry Garcia, the National Geographic’s chief science and exploration officer. “That’s why, when National Geographic received a call from (lead researcher) Lee Berger reporting the fossils’ initial discovery, we immediately committed our support to this remarkable effort.”

Researchers from Wits University, the National Geographic Society and the South African government announced the discovery Wednesday with an article scheduled for publication in the October issue of National Geographic magazine and a NOVA/National Geographic television special, “Dawn of Humanity,” scheduled to be broadcast Wednesday on PBS.

National Geographic officials said they learned of the new species “only because a couple of cavers were skinny enough to fit through a crack in a well-explored South African cave,” with Berger noting that the species’ combination of anatomical features “distinguishes it from any previously known species.”

The team speculated that H. naledi, with its relatively large body for a primitive species and small brain the size of an orange still had the wherewithal to dispose of bodies in ritualistic fashion inside the cave chamber. But that’s a point of controversy. The bodies were put there at different times with no evidence of the catastrophic demise of all of the individuals, the team said.

The age of the fossils and H. naledi’s place in the genus Homo aren’t yet determined. But the new human relative is sure to add pieces to the puzzle of human evolution with the big question of how Homo sapiens ended up as the genus’ sole survivor.

Heather Garvin, 32, an assistant professor of anthropology at Mercyhurst University in Erie, Pa., was an early-career scientist who did 3-D imaging to determine H. naledia’s cranial size while working with a team that described its stature. The body was large for a primitive human species, she said, but its small brain counters traditional belief that body and brain simultaneously grew larger throughout evolution.

“Its body size was in the range of modern humans but on the small end of that range,” she said. “The foot looks fairly modern with slight differences. You wouldn’t expect them to walk much differently than we do, but it still had tree-climbing capability,” as indicated by curved finger bones.

“Here you have a small-brain human with tool-making capability that walked on two legs and deposited its dead in a cave. That shows humanlike behaviors. In that way, it is changing the way we are thinking about brain size,” said Garvin, who holds a doctorate in functional anatomy and evolution.

It also adds more evidence that human evolution may have been more like a bush with many species following different evolutionary paths before extinction rather than the upside down tree leading to Homo sapiens.

Noted University of Pittsburgh anthropologist Jeffrey H. Schwartz questions whether H. naledi should even be included in the genus Homo with many characteristics similar to species in the primitive hominid genus Australopithecus. He said one of three skulls discovered in the cave was unlike the other two, suggesting perhaps two new species, with all three representing nothing ever seen to date in any human species.

“Speculation about burial and rituals is a little over the top,” Schwartz said. “Until you sort out the real morphology of this species, it is premature to say anything about it, including why they were in a cave. They are jumping the gun,” he said.

Some fossil specimens seem to be like us, while others are more like Australopiths, he added.

“Why do all belong to the same species? Because they were found in the same cave, but the published images tell a different story,” Schwartz stated in a written response to the discovery. “Even at this stage of their being publicized,” he said, “The ‘Homo naledi’ specimens reflect even greater diversity in the human fossil record than their discoverers will admit.”

(c)2015 Pittsburgh Post-Gazette

Visit the Pittsburgh Post-Gazette at www.post-gazette.com

Distributed by Tribune Content Agency, LLC.