Another species of man lived alongside of us, modern humans, in Africa relatively recently, according to an international study in which LSU participated.
It’s the first time scientists have demonstrated that another species in the family of humans, sharing some of the same traits as our ancestors, lived near the first modern humans in Africa, said Juliet Brophy, LSU Department of Geography & Anthropology assistant professor and co-author of one of several related scientific journal articles published Tuesday. Homo sapiens began in Africa, then migrated around the world.
Homo naledi was a primitive, small-brained hominin whose remains were found in the Dinaledi Chamber of the Rising Star Cave near Johannesburg, South Africa.
Brophy was involved in the discovery of Homo naledi, a newly discovered human species, at the cave in 2015. She said the bone fragments of the species showed a much more primitive structure than modern humans. But the scientists didn't know how old the specimens were.
"If the dating came back as 2 million years old, I don't think any one of us would have raised an eyebrow," she told The Advocate Tuesday.
But a combination of techniques by different scientists, working independently, determined that the specimens were much younger. That put the age of the newly discovered species at somewhere between 335,000 and 236,000 years ago – when modern humans lived in Africa.
“Once modern humans were around, there were no other competing hominid species in Africa, and now there is one,” Brophy said. “When you have two species that share a similar ecological niche, they have to adapt or one of them goes extinct.”
A second room, called the Lesedi Chamber, was discovered in the Rising Cave system that contained additional 131 hominid pieces. These discoveries included a child and a partial skeleton of an adult male with a remarkably well-preserved skull.
Homo naledi had primitive characteristics that scientists wouldn’t have expected in a species living at a time of Homo sapiens, she said.
For instance, the pelvis was shaped to allow walking upright, but not for long distances when compared to modern humans. They had curved fingers and a shoulder girdle, which suggest Homo naledi individuals could climb easily.
But at the same, the species shared some traits with modern humans.
The shape of the Homo naledi skull is very modern, with a large forehead, just like Homo sapiens. But the brain cavity is small – less than half the size of modern humans.
“We used to think that brain size got bigger and the skull shape changed after that. But now it looks like that basically the skull reorganized in shape and then the brain got bigger. Oh, it’s awesome,” Brophy said.
During her earlier visit to Africa, Brophy developed a large digitized database of ancient teeth, which can be used to identify species and track the changes within species.
"My colleagues and I examined the teeth from the second chamber. In particular, we described the lower left deciduous, or juvenile, second molar, or dm2,” Brophy said.
They compared the teeth to what was found in the Dinaledi Chamber as well as with other specimens. “The deciduous tooth is nearly identical to that of the teeth from Dinaledi. Furthermore, the morphology of the juvenile and adult permanent teeth support their taxonomic designation to homo naledi.”
The discovery of the second chamber led the team to take the controversial position that Homo naledi deliberately disposed of its dead in these remote, hard to reach caverns, according to the scientific journal article. Modern humans also dispose of their dead. The remains were dated to a period called the late Middle Pleistocene, when it was previously thought that only Homo sapiens, or modern humans, existed in Africa.
"More critically, it is at precisely this time that researchers see the rise of what has been called “modern human behavior” in southern Africa – behavior attributed, until now, to the rise of modern humans and thought to represent the origins of complex modern human activities such as burial of the dead, self-adornment and complex tools," the study posited.
The research was published Tuesday in three papers in the journal eLife.
The new discovery and research was done by a large team of researchers from the University of the Witwatersrand, or Wits, in Johannesburg, South Africa; James Cook University, Australia; LSU; the University of Wisconsin, Madison; and more than 30 other institutions.
The team was led by Wits Professor Lee Berger, who is a National Geographic Explorer in Residence.