Discovery of Homo naledi Raises Questions About Our Evolutionary Past

An international team of scientists, including one from the University of Colorado Denver and another from the University of Colorado Anschutz Medical Campus in Aurora, announced the discovery Thursday of a new species of hominin, a small creature with a tiny brain that opens the door to a new way of thinking about our ancient ancestors.

The discovery of 15 individuals, consisting of 1,550 bones, represents the largest fossil hominin find on the African continent.

“We found adults and children in the cave who are members of genus Homo but very different from modern humans,” said CU Denver Associate Professor of Anthropology Charles Musiba, PhD, who took part in a press conference Thursday near the discovery inside the Rising Star Cave in the Cradle of Humankind World Heritage Site outside Johannesburg, South Africa. “They are very petite and have the brain size of chimpanzees. The only thing similar we know of are the so-called `hobbits’ of Flores Island in Indonesia.”

Homo floresiensis or Flores Man was discovered in 2003. Like this latest finding, it stood 3.5 five feet high and seems to have existed relatively recently though the exact age is unknown.

Caley Orr, PhD, an assistant professor of cell and developmental biology at the University of Colorado School of Medicine, analyzed the fossil hands.

“The hand has human-like features for manipulation of objects and curved fingers that are well adapted for climbing,” Orr said. “But its exact position on our family tree is still unknown.”

The new species has been dubbed Homo naledi after the cave where it was found – naledi means `star’ in the local South African language Sesotho.

One of the most intriguing aspects of the discovery is that the bodies appear to have been deposited in the cave intentionally. Scientists have long believed this sort of ritualized or repeated behavior was limited to humans.

The team of 35 to 40 scientists was led by Lee Berger, research professor in the Evolutionary Studies Institute at the University of Witwatersrand in South Africa. It was supported by the National Geographic Society and the National Research Foundation. The October issue of National Geographic magazine will feature the discovery as its cover story. It will also be the subject of a NOVA/National Geographic Special airing Sept. 16.

Image shows bone fragments of Homo naledi.

Fragments of Homo naledi, a new species of hominin recently discovered in South Africa. Credit: University of Colorado Denver.

Getting inside the Dinaledi chamber of the remote cave system was difficult, requiring the help of six `underground astronauts,’ who squeezed through a 7-inch wide gap to reach the remains.

“The chamber has not given up all of its secrets,” said Berger, a National Geographic Explorer-in-Residence. “There are potentially hundreds if not thousands of remains of H. naledi still down there.”

The announcement coincides with the publication of two studies about the new species in the journal eLife, co-authored by Musiba and Orr.

In it, the researchers try to place Homo naledi in context with other species. Generally speaking, they say, there is an assumption that any new group of fossils must belong to an existing species.

But it’s not that simple here.

“Assigning these remains to any known species of Homo is problematic,” the study said. “While Homo (naledi) shares aspects of cranial and mandibular morphology with Homo habilis, Homo rudolfensis, Homo erectus, MP Homo and Homo sapiens, it differs from all of these taxa in its unique combination of derived cranial vault, maxillary, and mandibular morphology.”

Image of teeth and bone fragments.

One of the most intriguing aspects of the discovery is that the bodies appear to have been deposited in the cave intentionally. Scientists have long believed this sort of ritualized or repeated behavior was limited to humans. Credit: University of Colorado Denver.

The study suggests that Homo naledi most closely resembles Homo erectus with its small brain and body size. Yet it also resembles Australopithecus which highlights its own uniqueness.

Complicating matters is the fact that researchers still don’t know the exact age of the fossil site.

“If these fossils are late Pliocene or early Pleistocene, it is possible that this new species of small-brained, early Homo represents an intermediate between Australopithecus and Homo erectus,” the study said.

That would also make the new species very old.

But if the fossils are more recent, they theorize, it raises the possibility that a small-brained Homo lived in southern Africa at the same time as larger brained Homo species were evolving.

“This raises many questions,” Musiba said. “How many species of human were there? Were their lines that simply extended outward and then disappeared? Did they co-exist with modern humans? Did they interbreed?”

Homo naledi has a chest similar to a chimpanzee and hands and feet proportionate with modern humans, though with curved fingers.

“They would have had great climbing ability,” said Musiba. “The oldest adults were about 45 and the youngest were infants.”

He described poring over the bones late at night as akin to `hitting the jackpot.’

“You just didn’t want to go home because it was so exciting,” he said. “I felt like a kid in a candy store.”

The find represents another milestone in Musiba’s efforts to advance the understanding of our earliest human relatives.

As director of CU Denver’s Tanzania Field School, he takes groups of students each year to gain hands-on experience working in and around the famed Laetoli hominin footprints site and Olduvai Gorge where some of the oldest hominin remains have been found.


Charles Musiba, PhD, was part of a team of anthropologists that recently discovered a new species of hominin in South Africa that may have existed alongside modern humans. The discovery is raising interesting new questions about human evolution.

Not long ago, they discovered ancient footprints of lions, rhinos and antelopes near those of the early hominins.

And last year, Musiba was appointed to an international team of advisors dedicated to building a museum complex in Tanzania to showcase a collection of 70 hominin footprints, estimated at 3.6 million years old. They are considered the earliest example of bipedalism among hominins.

Musiba said the Rising Star expedition was notable for getting so many anthropologists to work together.

“Anthropology can be a cut-throat profession with all these scientists scrambling for limited resources,” he said. “To me one of the most exciting aspects of this research was the collaborative nature of it.”

About this evolution research

Source: David Kelly – University of Colorado Denver
Image Source: The images are adapted from the University of Colorado Denver press release
Video Source: The video is available at the University of Colorado Denver YouTube page
Original Research: Full open access research for “Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa” by Lee R Berger, John Hawks, Darryl J de Ruiter, Steven E Churchill, Peter Schmid, Lucas K Delezene, Tracy L Kivell, Heather M Garvin, Scott A Williams, Jeremy M DeSilva, Matthew M Skinner, Charles M Musiba, Noel Cameron, Trenton W Holliday, William Harcourt-Smith, Rebecca R Ackermann, Markus Bastir, Barry Bogin, Debra Bolter, Juliet Brophy, Zachary D Cofran, Kimberly A Congdon, Andrew S Deane, Mana Dembo, Michelle Drapeau, Marina C Elliott, Elen M Feuerriegel, Daniel Garcia-Martinez, David J Green, Alia Gurtov, Joel D Irish, Ashley Kruger, Myra F Laird, Damiano Marchi, Marc R Meyer, Shahed Nalla, Enquye W Negash, Caley M Orr, Davorka Radovcic, Lauren Schroeder, Jill E Scott, Zachary Throckmorton, Matthew W Tocheri, Caroline VanSickle, Christopher S Walker, Pianpian Wei, and Bernhard Zipfel in eLife. Published online September 10 2015 doi:10.7554/eLife.09560


Abstract

Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.

Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa” by Lee R Berger, John Hawks, Darryl J de Ruiter, Steven E Churchill, Peter Schmid, Lucas K Delezene, Tracy L Kivell, Heather M Garvin, Scott A Williams, Jeremy M DeSilva, Matthew M Skinner, Charles M Musiba, Noel Cameron, Trenton W Holliday, William Harcourt-Smith, Rebecca R Ackermann, Markus Bastir, Barry Bogin, Debra Bolter, Juliet Brophy, Zachary D Cofran, Kimberly A Congdon, Andrew S Deane, Mana Dembo, Michelle Drapeau, Marina C Elliott, Elen M Feuerriegel, Daniel Garcia-Martinez, David J Green, Alia Gurtov, Joel D Irish, Ashley Kruger, Myra F Laird, Damiano Marchi, Marc R Meyer, Shahed Nalla, Enquye W Negash, Caley M Orr, Davorka Radovcic, Lauren Schroeder, Jill E Scott, Zachary Throckmorton, Matthew W Tocheri, Caroline VanSickle, Christopher S Walker, Pianpian Wei, and Bernhard Zipfel in eLife. Published online September 10 2015 doi:10.7554/eLife.09560

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