“It’s not a normal commute,” says paleoanthropologist Marina Elliott, a post-doctoral fellow at South Africa’s University of the Witwaterstrand. She’s talking about the precarious, hour-long descent into Rising Star cave, located in the UNESCO-designated Cradle of Humankind. “It’s a little bit dangerous,” she begins, then revises. “Okay, a lot dangerous.”

Only accessible by a 40-foot-long chute studded with rows of sharp perturbations, like the teeth in a shark’s mouth, her workplace—an active fossil dig—is also nearly 100 yards from the cave entrance. “Even a minor accident would necessitate a huge rescue effort,” she explains. “They can’t send emergency equipment in there. You’d have to live [in the cave] until you are able to get yourself out.” Yet it’s a path she’s taken countless times since 2008. After all, she says, “it’s not a normal job.”

Part of a team of scientist-slash-spelunkers first recruited in 2008 by prominent paleoanthropologist Lee Berger, Elliott was the first of the group to enter the especially difficult-to-access Dinaledi chamber inside Rising Star. Berger’s team of roughly 60 scientists, six of whom who climb in and out of Dinaledi, have unearthed a staggering number—thousands—of early hominid fossils: the most ever found anywhere in Africa. “It’s pretty daunting,” Elliott says, “because we’ve only really scratched the surface.”

Few stories are as compelling—or incomplete—as that of human evolution. Our interest is self-evident: who doesn’t love an origin story, especially when it is our own? Yet this particular narrative is remarkably young. The theory of evolution by natural selection is barely 150 years old. The first evidence than humans evolved in Africa is less than 100. The world has believed it for barely 70.

Berger is almost as famous for his skill as a storyteller as he is for his astonishing discoveries: two new species of early hominids—Australopithecus sediba at Malapa and Homo nalendi at Rising Star—in the Cradle of Humankind. He feels the history of the place keenly; not only that of early humans but of modern humanity’s quest for them. “This is where the search for human origins in Africa began.”

WANT TO SEE SOUTH AFRICA? Take a trip with PopSci editors!

Discovered in 1924 in a lime quarry 30-miles north of Johannesburg, the skull did not—as was first assumed—belong to a baby ape. While apelike, the individual bore human characteristics: the opening at the base of its skull suggested that the Taung child, as it came to be known, walked upright, as no known ape did. Anatomist Raymond Dart declared it a new species, Australopithecus africanus, and proof that humanity evolved in Africa. (Rather than Europe or Asia, as most scientists believed at the time.) Yet it was only when Scottish paleontologist Robert Broom substantiated Dart’s work with a 1946 monograph following a decade of excavating—often with dynamite—adult A. africanus remains in the nearby Sterkfontein caves that South Africa was first broadly recognized as the “Cradle of Humankind.”

But the “cradle” designation shifted. The Leakeys, in 1960, discovered a new species in Tanzania that appeared to fit somewhere in between A. africanus and us, and named it Homo habilis . Donald Johanson discovered Lucy, the most famous non-human hominid ever, in Ethiopia in 1974. In South Africa, nothing new was found for decades.

“A lot of that is tied with the politics of apartheid,” Berger reflects, a history that is depicted in the museums within the Cradle of Humankind. “You get this fascinating blend of the deep history of the science and one of the darkest periods of human history—the end [of which] is celebrated as well.”

It’s no wonder than the political and social context of scientific study affects its results, but that effect is magnified in a field like paleoanthropology, where specimens are few and far between. The discoveries in East Africa, “supported by a dearth of fossils coming out of South Africa,” Berger explains, supported the story that all the critical events in human evolution happened in one, rather than the other, region.

The truth is likely much more complex, and Berger is doing his best to complicate it. “Even a bush or a tree is wrong,” he says, dismissing some of the most common analogies for human evolution. “It’s more like a braided stream that meanders as it melts into a glacial lake.” It’s difficult, if not impossible, to say what water goes where, but there is a central tendency. “That lake is all 7-plus billion people alive today,” he says. “That glacier is the last common ancestor.”

Still, the sheer number of remains found in the Cradle of Humankind, and in Rising Star cave in particular, could support a story that humanity evolved in South Africa, rather than East Africa. What accounts for the outsize wealth of specimens?

“It’s because we’re looking here,” Berger admits. “The world’s not been explored.”

“Africa had animals, and potentially hominids, on it for millennia,” Elliott echoes. “It’s just an accident of circumstance that the geology”—dolomitic limestone, which punctured the landscape with fossil-sheltering caves—“has been exposed in South Africa, and that there was someone in the area in the 1920s to recognize it. There’s a tremendous amount of material that could still be found in places like Botswana, or the Democratic Republic of Congo.”

“We’re comparable for the drunk looking for his keys under the street lamp,” Berger adds. Rising Star is less than a mile from the longest running site in the field of paleoarcheology. “It was right under our noses.” What else could be out there?

Still, Berger says, South Africa is “the only place in the world where these discoveries are being made.” The Cradle of Humankind site makes it possible for visitors to go into Sterkfontein caves, to visit an active excavation, to see the original skeletal remains—an extraordinary level of access for nonscientists.

“To see those Homo nalendi fossils on display is extraordinary and moving,” Berger says. “They are the authentic thing, the largest collection of ancient human relatives.”

“They are out of place in time, out of place in geography,” he says, reflecting on the lack of contextual information in the caves where H. nalendi was found, and the challenges his team has faced in both dating the remains and explaining how they got there. His theory—one that has met much controversy —is that H. nalendi disposed of their dead, that the cache of remains at Rising Star were put there on purpose.

“It’s almost like an episode of Star Trek , where we humans meet an ancient, complex, nonhuman creature. They may be almost as complex as us, yet still fundamentally unhuman. And we don’t understand their relationship to us, if we even have one.”

But the research continues. A new paper in eLife proposes that H. nalendi lived relatively recently—only 335 and 236 thousand years ago—and alongside H. sapiens . “If there is one other species out there that shared the world with ‘modern humans’ in Africa, it is very likely there are others,” Berger explained in a university press release. “We just need to find them.”

Even in Dinaledi, where a decade’s worth of work has yielded record-setting numbers of early hominid remains, “we’ve really only excavated a 20th of the space,” says Elliott. “There’s no lack of work to do.”