Primitive hominids may have lived in Africa at the same time as humans, researchers said Tuesday, in new findings that could change the understanding of human evolution.
Fossils found deep in South Africa’s Rising Star cave complex in 2013 have been dated by several expert teams with their findings suggesting the hominids, called Homo Naledi, may have lived alongside Homo sapiens.
It had previously been thought that the hominids were millions of years old.
A team of 20 scientists from laboratories and institutions around the world, including in South Africa and Australia, established the age of the fossils which suggests that Homo Naledi may well have lived at the same time as humans. Their findings have been published Tuesday in three papers in the journal eLife.
The focus of the team’s research has been South Africa’s barely accessible Rising Star Cave system, part of the Cradle of Humankind World Heritage Site, about 50 kilometres (30 miles) north-west of Johannesburg. The area has been an incredibly rich source of artefacts for palaeontologists since it was first discovered.
“There has been a great deal of speculation on how old Homo Naledi was. Everyone who has examined the anatomy of Homo Naledi has suggested that it would be in the millions of years,” said project leader and researcher at Wits University, Lee Berger.
But now, having established the age of the fossils using six independent methods, the team estimates that they are between 236,000 and 335,000-years-old — the beginning of the rise of modern human behaviour, said Berger.
Researcher John Hawks said that the separate discovery of new Homo Naledi fossils — including a pristine skull — in two other caves “confirmed that we’re looking at an anatomical pattern that is very different from any other common species”.
Some experts disputed the findings of the team that discovered the initial fossils and named the new species Homo Naledi, arguing that they were merely early Homo erectus.
“We’re looking at a diversity of species in Africa in the latest stages of our evolutionary history that no one had suspected would be there,” said Hawks, an academic at the University of Wisconsin in the United States.
“That implies that as our species arose, it arose with others, that there were a diversity of hominid species in Africa occupying these environments during what we had considered to be the critical time period of modern human origins.”
Work has begun to also date the latest fossils to be found.
Paul Dirks, a professor at Australia’s James Cook University which is involved in the project, said that Homo Naledi’s hand structure and the more recent era in which it is thought to have lived means it could have been a toolmaker.
The new findings have shown that the history of evolution is far more complicated than a straightforward sequential history, he said.
“We have many different branches on the family tree and it is only fairly recently that there is only one survivor on the landscape. The new dating of the fossils opens up all sorts of possibilities for an interchange of… behaviours between Homo Naledi and Homo sapiens,” Dirks added.
“This will have a profound effect on archaeology… (it is a) critical missing part of what happened in human evolution,” said Berger, who described the findings as “a Rosetta Stone for us”.
Homo Naledi had a tiny brain, about the size of an orange and stood about 1.5 metres (5 feet) tall, weighing around 45 kilogrammes (100 pounds), experts say.
Homo Naledi’s teeth and skull are similar to those of early humans while their shoulders are more similar to those of apes.
They had a brain about a third of the size of a modern human brain and curved fingers that are seemingly well suited for climbing.