
About 1,500 fossils were found deep in a cave system outside Johannesburg, hidden in a deep underground chamber only accessible via several steep climbs and rock crevasses.
Experts are uncertain how the "Homo naledi" remains got there, or even how old they are, but the discovery could shed fresh light on the origin of the mankind.
The bones were first discovered in 2013 by Witwatersrand University scientists and volunteer cavers in the Cradle of Humankind, a UNESCO World Heritage Site, 50 kilometres (30 miles) northwest of Johannesburg.
"I am pleased to introduce you to a new species of human ancestor," Lee Berger, research professor at the University of the Witwatersrand in Johannesburg, told reporters at the site.
Ancient human remains have been found in the area since excavations begun in the 1920s.
"The discovery of so many fossils belonging to at least 15 individuals is remarkable," said Professor Chris Stringer, from the Natural History Museum in London, one of the lead analysts on the discovery. ?AFP