Scientists say a human-like species discovered in an African cave lived at the same time as early African humans.
The Homo naledi was a combination of modern human-like and less evolved ape-like characteristics, such as having a small brain. Fossil dating showed it existed between 236,000 and 335,000 years ago.
"This is astonishingly young for a species that still displays primitive characteristics found in fossils about 2 million years old, such as the small brain size, curved fingers and form of the shoulder, trunk and hip joint," Chris Stringer of the Natural History Museum in London wrote in an email to The Associated Press.
"Yet the wrist, hands, legs and feet look more like those of Neanderthals and modern humans, and the teeth are relatively small and simple and set in lightly built jawbones."
Scientists say the discovery shows the human family tree still contained greater diversity during that period than previously thought.
"How did a comparably strange and small-brained species linger on in southern Africa, seemingly alongside more 'advanced' humans?" Mr Stinger says.
Other human-like species currently being examined include the 'hobbit species' Homo floresiensis, which lived on an isolated island in what is now Indonesia.
Researcher John Hawks, from the University of Wisconsin-Madison and Wits University, says the next step will be to "sort the relationship of these different species to each other and also their role in our process of becoming human".
While there is no evidence the small-brained species could use fire or use stone tools, scientists hope the Homo naledi discovery will stop racism and intolerance from spreading.
"This research shows that we come from common roots, that we represent a common humanity," says Wits University vice-chancellor Adam Habib.
"If we're going to survive as a species, that's what we need to remember."