In 2015 it was a discovery described as "unlike anything we have seen." Now even more so. A second chamber in a South African cave system has produced bones belonging to Homo naledi, a species scientists now believe may have existed around the same time as Homo sapiens and that the Washington Post describes as "an enigma." Per new research published Tuesday in eLIFE, the newly found bones in the Lesedi Chamber of the Rising Star caves belong to at least three individuals but have not been dated. Those of the 15 individuals unearthed in 2013 in the Dinaledi Chamber have now been determined to be 236,000 to 335,000 years old—which shocks some scientists, as that would place the species as existing around the time of early modern humans.
The bones reveal so little stress or disease that scientists wonder if H. naledi was the area's dominant species. "They are the healthiest dead things you'll ever see," study author Lee Berger tells the Guardian. And they're raising a lot of questions, like whether H. naledi could have fashioned some of the tools found in the area, and, as the Post puts it, whether "paleoanthropologists shift their focus from East Africa to the continent's less-studied southern regions." The Dinaledi Chamber is so hard to access that an all-female team of tiny spelunkers was used; there's no route from it to the Lesedi Chamber, which is 100 feet underground. Some speculate the bones' presence in two chambers means the species buried its dead. Outside scientists are doubtful; one expresses the possibility that a sinkhole or some undiscovered entrance may still be found. (Did humans live in California 130,000 years ago?)