New Homo naledi discovery raises questions over origins of humankind
Nearly two years after scientists from Wits University announced the discovery of a new species - Homo naledi - they have managed to determine its age. The fossils were surprisingly young, bringing into question much of what experts in the field previously believed, including the evolution of modern humans.
Scientists at the University of the Witwatersrand have successfully dated the fossils found in the Cradle of Humankind back in 2013.
The previously unknown species - Homo naledi - was first announced in 2015 - two years after the bones were excavated from the Dinaledi Chamber in the Rising Star cave system, west of Johannesburg.
Scientists used various dating methods and were surprised to find that Homo naledi is between 335-and 236 000 years old - a youngster in evolutionary terms.
The finding suggests Homo naledi could have co-existed with Homo sapiens - the first direct ancestors of modern humans - as they made their way to the top of the food chain. "That implies that as our species arose, it arose with others," says lead author Prof. John Hawks. It further raises questions over whether Homo naledi could be directly linked to human ancestry.
Scientists previously believed only Homo sapiens walked the earth during the period known as Middle Pleistocene. "Homo naledi is there, archaic humans are there, the ancestors of potentially the earliest humans are there," says Hawks.
Prof. Paul Dirks worked with 19 other scientists to determine the age of the fossils. He says six independent methods were used as the bones were tested in labs in both South Africa and Australia.
The species is known as a primitive small-brained hominin and according to Prof. Lee Berger, who lead the team in the initial discovery, Homo naledi's anatomy suggest the origin of this species dates back millions of years.
It shares features with some of the earliest known hominins including Homo rudolfensis and Homo habilis.
Both are believed to have lived in Africa around two million years ago. "…Which means that this species… existed down through time to come to a point, at the same time where we suspect there are other species on the continent of Africa," explains
Berger, "and those species are all big-brained and may be the direct ancestor of modern humans." It further suggests Homo naledi co-existed with a number of other hominins other than humans - while scientists previously believed there existed only one species at a time.
This new information also has implications for the study of archeology.
Hawks says Homo naledi's young age also casts doubt over which species made use of the tools and other artefacts found on the continent, which have also been dated back to same period.
The new discovery
Berger's team has also discovered more skeletal fossils, including the remains of a child and two adults. These were found in a chamber located around 100m from the Dinaledi Chamber known as Lesedi.
The skull of one of the adults, believed to be male, has been well preserved and has been named Neo - meaning 'a gift' in Sesotho. It is also considered one of the most complete skeletons ever discovered.
The new fossils are helping scientists get a better understanding of Homo naledi, especially Neo's skull. "So we are for the first time getting a look at the face of this species," says Hawks.
The anatomy of the fossils found in the Lesedi Chamber bear striking similarities to those found in Dinaledi. And while the Lesedi fossils have not been dated, the scientists believe they come from the same period.
While Berger believes there are thousands of other fossils in the Rising Star cave system, they have halted extraction operations. He believes there are decades worth of research potential buried in the area but believe some material should be preserved for future generations, which might have access to more advanced technology.
Regardless, experts in the field might be occupied with the latest developments for some time to come. "Now we face mysteries that we had not suspected," says Hawks.
"We have clearly in Homo naledi a very primitive species in its brain size and in many aspects of its anatomy that is doing very human-like things within that cave system."