Remains of Child From Mystery Human Species That Lived 300,000 Years Ago Discovered

Researchers have unearthed the remains of a young Homo naledi, the most recently discovered ancient human relative. The authors of the research article, published in PLOS ONE, say the find could improve our understanding of this mysterious species.

The findings belonging to an juvenile individual named DH7 are among the few pre-adult skeletal remains on the fossil record. The majority of those found are from adults, whose bones are tougher, less porous and more likely to survive the hundreds of thousands of years.

DH7's young age offers anthropologists a chance to study the development of young hominids. Bones from this particular individual were among a large collection found in the Dinaledi Chamber of the Rising Star Cave System in South Africa, dating to a period between 335,000 and 226,000 years ago, during the Late Middle Pleistocene.

Though the remains of DH7 are incomplete, they offer clues to how old the individual was when they died. DH7 displays a mix of maturity patterns—specifically, well-developed but unfused bones—indicating the H. Naledi was a late juvenile. However, the exact age is harder to determine because the speed of maturation in the species is unknown.

If H. Naledi matured at the speed of earlier, more ape-like hominids, the maturity patterns suggest it is between 8 and 11 years old. But, the study's authors say, it is possible that it matured at a slower pace, similar to Homo sapiens and Neanderthals—both of which were roaming the planet 300,000 years ago. If that was the case, DH7 may have been as old as 15.

"There are very few pre-adult skeletons in the fossil record," Debra Bolter, Professor of Anthropology at Modesto Junior College in California, and Honorary Researcher, Evolutionary Studies Institute, University of Witwatersrand, South Africa, told Newsweek.

"The ability to associate the remains of an older juvenile H. naledi is a major break-through in paleoanthropology. Immature remains are critical for understanding how an extinct species matured," said Bolter.

Homo naledi skull
Paleoanthropologist Professor Lee Rogers Berger holds a replica of the skull of "NEO" a new skeleton fossil findings of the Homo Naledi Hominin species. Taken on May, 9 2017 in South Africa. Anthropologists have identified the bones of a juvenile H. Naledi. GULSHAN KHAN/AFP/Getty

"The pattern of skeletal maturation seen in the elements assigned to DH7 could be observed in humans and in other apes," Louise Humphrey, a researcher at the Natural History Museum in London, told Newsweek. "It does not exclude a slower, more human-like pace of development or an intermediate pace or a unique pace and pattern of development in Homo naledi, with subtle differences from both humans and other living apes."

She added: "Further research to establish an age at death from the dentition would provide greater insights into the timing of development in this species."

H. naledi is the most recently discovered member of the hominid family. The species, described in 2015, displays a mix of primitive and human-like features, with its hands, wrist and feet appearing more like Homo sapiens or Neanderthal, while its upper body and small brain size appear more primitive.

The bones found in the Rising Star Cave System date H. naledi to a period between 335,000 and 226,000 years ago, overlapping the arrival of modern humans. Neanderthals evolved approximately 400,000 years ago in Eurasia, while the first H. sapiens, or modern humans, emerged in Africa approximately 300,000 years ago.

These fossils place H. naledi relatively late on the evolutionary timeline, a fact that has confused paleontologists given their more primative characteristics akin to australopiths like the Australopithecus afarensi "Lucy." When they were first discovered, many expected the bones to be older and some academics have debated the use of the word "Homo" in their name.

Bolter is hopeful that future research could produce a more accurate reading on DH7's age, thus revealing whether the species was more ape-like or human-like in its maturation. Tooth microhistology, for example, may be used to calculate an age-at-death for immature remains from daily and weekly enamel secretions in a similar way to tree-ring dating.

"H. naledi stands out among other extinct hominin species because of its mixture of primitive australopith features, like a small brain and outwardly flared hip bones, in combination with human-like hands, feet and dentition, plus distinctive traits like heavily muscled thumbs," said Bolter.

"Future research will help us answer the developmental mysteries surrounding H. naledi, whether the pace of growing up and the pattern of dental-skeletal maturity are more primitive, are human-like, or some unique combination of the two."

Homo naledi juvenile remains
Homo naledi juvenile remains offers clues to how our ancestors grew up. Bolter et al. PLOS ONE 2020 CC BY