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Cave women unearth skull of unknown human ancestor

An all-woman team of spelunking scientists has retrieved hundreds of fossils from a 100-foot-deep (30-meter-deep) cave in South Africa — including the cranium from what appears to be a prehistoric humanlike creature.

Friday's retrieval of the skull was a climactic moment for the three-week expedition to the Rising Star Cave in South Africa's Cradle of Humankind World Heritage Site, just 25 miles (40 kilometers) north of Johannesburg. 

The Rising Star Expedition, backed by the National Geographic Society, was put together after a pair of recreational cavers came upon the trove of bones last month. They alerted Lee Berger, a paleoanthropologist at the University of the Witwatersrand who has been behind a long string of significant finds in South Africa and serves as a National Geographic explorer-in-residence.

Berger was excited to hear that the fossilized bones could represent a new group of hominins. ("Hominins" has become the preferred term for humans and our close extinct relatives, such as Neanderthals. Scientists now use the term "hominids" to refer to those species as well as to gorillas and chimpanzees.)

The call went out for scientists to join the expedition. Some of the top experts in paleoanthropology, such as the University of Wisconsin's John Hawks and Duke University's Steven Churchill, joined the team. But the scientists tapped to go into the cave and bring up the fossils were required to have an almost superhuman combination of talents.

They had to have a master's degree or Ph.D. in paleontology, archaeology or an associated field. They had to be experienced cavers. And they had to be able to fit through a 7-inch-wide (18-centimeter-wide) choke point in the passage leading to the chamber. Fifty-seven qualified researchers applied for the job. Six were chosen: Lindsay Eaves, Marina Elliott, Elen Feuerriegel, Alia Gurtov, Hannah Morris and Becca Peixotto.

"It ended up that the most qualified human beings on this planet to do this very dangerous, very remarkable job were young women," Berger said in a video profile of the "underground astronauts."

The project is already paying off big time. "Wonderful fossils coming out now," Berger tweeted from the site on Friday.

The cranium and a hominin jawbone were among the most-prized specimens. "Cuddled the cranium all morning, then made first run carrying fossils entire way. Getting the hang of this!" Gurtov reported.

By the end of the day, a box containing the cranium was carefully handed up from the depths by a human chain. "Lots of celebration out here. Rising moon, beautiful evening, and twenty celebrating people," Hawks wrote.

Gurtov exulted over the skull's retrieval. "CRANIUM IS OUT! No revealsies until tomorrow, though," she tweeted. "Needs pampering."

Berger said more than 200 hominin fossils have been brought up so far. After coming up to the surface, the bones are taken into a "SCIENCE" tent where they're compared with replicas of previously found hominin skulls and other bones.

For now, the team is holding back on saying where the Rising Star fossils fit on humanity's evolutionary tree. Berger said he expected a scientific paper on the find would be prepared for publication in late 2014. Meanwhile, National Geographic and the "Nova" science documentary team are working on a TV show about the expedition.

In a National Geographic blog posting, Hawks noted that the Rising Star Expedition was atypical for the usually secretive field of paleoanthropology:

"Why are so many projects so secretive? Discovery is hard work — both in the field and in the laboratory. Other scientists can be brutal critics, pointing out flaws in early interpretations. Sometimes they even steal your work. Our field has historically been a shark tank, and sharing makes the sharks start circling.

"We believe that sharing will make our science better. Rising Star is the most open paleoanthropological project that has ever been attempted. We’re experimenting with new ways of sharing the experience. Lee brought together the team of advance scientists by putting out a call on Facebook. National Geographic has been incredibly supportive, with their crew onsite to share updates and video. The senior scientists are sharing updates on Twitter and Facebook, many events as they are happening — follow @LeeRBerger, @RisingStarExped and @johnhawks.

"This three-week expedition is only the beginning of our innovation. As we analyze the fossils, we are going to continue new experiments with sharing and open access. We’ve got some incredible things planned."

More about human evolution:

For updates on the South African adventure, check out National Geographic's Rising Star Expedition blog and YouTube channel.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.