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A newly discovered early human ancestor could have used tools and may have even figured out how to bury its dead, scientists said Thursday — a find they said was "unlike anything that we have seen" in the fossil record.

The new species, dubbed Homo naledi for the South African cave where more than 1,550 numbered fossil elements were discovered, was announced in Johannesburg, South Africa, by the University of the Witwatersrand, the National Geographic Society and the South African Department of Science and Technology/National Research Foundation.

A reconstruction of what Homo naledi is believed to have looked like. The newly discovered human ancestor was about 5 feet tall with a brain the size of an average orange. National Geographic Society

At about 5 feet tall and only 100 or so pounds, and with a brain only about the size of an average orange, H. naledi is a startling combination of australopith-like and human-like features that, until now, was entirely unknown to science, researchers said.

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"Overall, Homo naledi looks like one of the most primitive members of our genus, but it also has some surprisingly human-like features — enough to warrant placing it in the genus Homo," said John Hawks, an anthropology professor at the University of Wisconsin at Madison and a senior author of a paper describing the new species.

The most remarkable conclusion from two years of study is that H. naledi may have intentionally and carefully buried its dead — behavior previously thought to be unique to humans.

Parts of at least 15 distinct individuals — infants, children, adults and elderly individuals — have been recovered from a chamber about 100 yards from the entrance to a cave called Rising Star in the Cradle of Humankind World Heritage Site northwest of Johannesburg. ("Star" translates as "naledi" in the local language — hence the name.)

The entrance to the chamber is so small that the team had to recruit specialist scientist-cavers slender enough to fit through the 7-inch-wide opening and retrieve the fragments, the National Geographic Society said. That suggests that the chamber was specifically used to shield the bodies, it said.

Scientist-cavers excavate Homo naledi fossils in a cave called South Rising Star in the Cradle of Humankind World Heritage Site northwest of Johannesburg, South Africa. National Geographic Society

Lee Berger, who led two expeditions to recover the fossils, said numerous scenarios were explored to explain the isolation and preservation of the fragments — "including mass death, an unknown carnivore, water transport from another location or accidental death in a death trap, among others."

"In examining every other option, we were left with intentional body disposal by Homo naledi as the most plausible scenario," said Berger, a research professor of evolutionary studies at the University of the Witwatersrand.

Such a situation, Hawks said, "is unprecedented in the fossil hominin record."

The discovery, which will be featured as the cover story of National Geographic magazine's October issue and on PBS' "NOVA" next Wednesday, represents only a small part of what's believed to be in the cavern, said Jamie Shreeve, National Geographic's executive editor for science.

"This chamber has not given up all of its secrets," Berger writes in the October issue. "There are potentially hundreds if not thousands of remains of H. naledi still down there.

"If we learned about a completely new form of hominin only because a couple of cavers were skinny enough to fit through a crack in a well-explored South African cave, we really don't have a clue what else might be out there," he said.