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Humanity’s ancient family tree is set to be shaken up by fossil skeletons found embedded in rock at a site near Johannesburg, South Africa. They could be from another long lost human cousin. “We have another major hominin discovery,” said Lee Berger at New Ů��С��Ƶ Live on Saturday.

In the past decade,  Berger at the University of the Witwatersrand in South Africa and his team has discovered not one but two new species of human ancestor.

In 2010, Berger made the headlines when he (or rather, his then 9-year-old son) discovered the remains of a new species of human in the hills north of Johannesburg. This was Australopithecus sediba, which lived around 2 million years ago and appears to be our closest ape-like ancestor.

Then, in 2013, Berger hit the fossil jackpot again, with the remarkable discovery of thousands of bones deep inside the Rising Star cave system also near Johannesburg. These turned out to belong to a new species of tiny, small-brained hominin called Homo naledi. This fossil hominin is transforming our understanding of human evolution, not least because H. naledi lived very recently, around 250,000 years ago, and has a strange mix of modern and archaic features.

But Berger is on a roll. The new fossil hominin remains he has discovered are located near the Rising Star caves, but the bones haven’t yet been excavated due to the challenging nature of their location. “It’s a difficult site,” said Berger, as the fossils are embedded in very hard rock.

So could this be another new species? “I don’t know. We haven’t got them out of the rock yet,” said Berger. “All I have is a glimpse of several individuals and that they are not very tiny.” The large size of the jaw and teeth means that the skeletons don’t belong to the diminutive H. naledi, and they are not A. sebida either, he said.

One possibility is that they are another species of the ape-like Australopithecus. Another is that they are an entirely new species. Fossil remains of our ancient cousins are exceedingly rare, so either way, these bones will shed new light on our deep family tree.

Buried treasure

But this is just one of many new sites with remains of hominins “known or unknown” awaiting excavation that Berger and his team have discovered. “We have a multitude of early hominin discoveries at different sites,” he said. “Now we’re in this period where it’s exploding, where we’re finding that these things are not as rare as we thought. We were often just looking in the wrong place or with the wrong eyes.”

While we wait for these bone treasure troves to be excavated we can expect new insights into H. naledi too. Although the first attempts to extract DNA from the skeletons didn’t succeed, studies are ongoing and will hopefully reveal where this species fits on the hominin family tree. “Molecular studies are in play,” said Berger.

Early next year we can also expect a study which reveals a relationship between H. naledi and another species, says Berger. “That will be big news,” he said. “These are exciting times.”