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GWEN IFILL: Researchers announced a fossil discovery today that some consider one of the greatest in the last 50 years, and one that could provide an important link in the family tree for all humans.
Jeffrey Brown has the story.
JEFFREY BROWN: The bones were found in a deep cave 30 miles northwest of Johannesburg. And the way they were found and then gathered is another incredible part of the story.
In all, 1,500 fossil remains were brought up and contained remains of 15 individuals of all different ages. Scientists named the new species Homo naledi and created this rendering.
The quest is chronicled in the new issue of “National Geographic” and in a special documentary airing on “NOVA” next week called “The Dawn of Humanity.”
Here’s a short clip.
NARRATOR: As the analysis goes on, the bones from the Rising Star cave are finally ready to be presented to the world.
MAN: We have got a new species of early human in the genus Homo, and that’s tremendously exciting.
We have never had anything in that transition period between the late Australopithecus and the earliest members of our genus in any kind of abundance, and, boy, we have it in abundance now.
NARRATOR: To members of the team, the fossils suggest a creature unlike anything ever found before.
MAN: We are looking at creatures that are humanlike in their feet, humanlike in their hands, humanlike in their teeth. Everything that interacts directly with the environment is Homo, and everything that’s sort of central, you know, the trunk, the architecture of the vertebral column, the brain, those sorts of things are more primitive. It’s like evolution is crafting us from the outside in.
JEFFREY BROWN: And joining me now is Jamie Shreeve, executive director for science at “National Geographic” magazine. He’s been involved with this project almost from the start. And Becca Peixotto is a member of the team. She was one of the so-called primary excavators who slipped through the caves’ narrower spaces to reach the fossil chamber.
Very interesting, very cool stuff, huh.
JAMIE SHREEVE, National Geographic: Very cool.
JEFFREY BROWN: Start with Jamie Shreeve .
Set the scene for us. This was an accidental finding.
JAMIE SHREEVE: Yes, pretty much.
A couple of cavers were exploring the cave site that’s been looked at. People train in it. It’s very well known, and they came across a little opening that’s only eight inches wide in some places. One of them took a step down, took another step down, and realized it just kept going down.
So they dropped into this cavern that had never been explored for, you know, who knows how long, and they found the floor of this cave littered with bones, with hominid bones.
JEFFREY BROWN: And, Becca Peixotto, that’s where you come in. Is it true that you were brought in through a social media? There was a call for small people who could do this kind of work?
BECCA PEIXOTTO, Excavation Team Member: There was an ad put out on Facebook, of all things, to find archaeologists, people who were qualified as archaeologists…
JEFFREY BROWN: That’s mind-blowing right there, right, from Facebook to this kind of a find. But go ahead.
BECCA PEIXOTTO: Exactly, yes.
So, small archaeologists who had some technical skills in climbing and caving. And that’s an unusual skill set, to have excavation skills and be comfortable working in a cave.
JEFFREY BROWN: And this is not your usual area.
BECCA PEIXOTTO: It’s true. I am normally an historical archaeologist, so I work on things from the last 500 years, and not things that are in the order of millions of years old.
JEFFREY BROWN: Well, so describe this scene for — the setting in the cave and the small chamber. What was it like to climb down there?
BECCA PEIXOTTO: Well, you drop down through a chute. You climb through a chute.
As Jamie said, it’s about seven or eight inches wide at its narrowest bits, which is quite skinny. And it’s a complicated climb. And there is a small landing zone, where we took off our shoes, and we entered the fossil chamber actually barefoot, because there is so much fossil material on the floor of the cave that, being barefoot, we were more conscious of where we were stepping to help find where the fossils were on the ground.
JEFFREY BROWN: And was it hard work? Was it — what was it like?
BECCA PEIXOTTO: We were working with toothpicks and paintbrushes, so toothpicks, real toothpicks.
And it’s very tedious work, exciting work, but you’re moving the soil away almost grain by grain in an effort to free the fossils from the matrix that they’re encased in without damaging them.
JEFFREY BROWN: So, Jamie Shreeve, what do we know so far about Homo naledi, as we just heard in that clip, humanlike from the outside, primitive on the inside?
JAMIE SHREEVE: Right.
We know this is a really bizarre thing. It’s nothing — nothing like it has been found before in the fossil record. It has a — this strange mix of characteristics that are very much like us.
For instance, the foot is virtually identical to a human foot, and yet the shoulder is more like an ape. Brain is a little pinhead brain. So, it’s a complicated equation that is proposed by this fossil.
JEFFREY BROWN: Researchers don’t yet know the age of it, I gather.
JAMIE SHREEVE: No, that’s the big question mark that’s outstanding, because once you have an age, you can really start telling the story of how this fits in with the story of human evolution.
JEFFREY BROWN: Well, when you say the feet are humanlike, does that suggest it was standing upright?
JAMIE SHREEVE: Oh, there is no doubt that this was an upright biped, and not only an upright biped, but one with — had long legs and feet constructed for probably a very efficient striding gate like ours, so it was definitely walking upright.
JEFFREY BROWN: The cave, I gather, is thought potentially to be, just by the sheer number of bones there and other remnants, to have been a burial site?
JAMIE SHREEVE: Well, the researchers don’t like to use the word burial.
JEFFREY BROWN: OK.
JAMIE SHREEVE: Because it has connotations of ceremony and an afterlife.
But it does seem to be that the most likely explanation for how these bones got into such a remote place was that they put there by other Homo naledi individuals, deliberately disposed of. Now, whether they had some intention of an afterlife or whether they were just getting rid of these bodies, nobody knows.
And, in fact, we really don’t know that’s the explanation, but that seems to be the best so far.
JEFFREY BROWN: You were in this place, whatever it was. What did it feel like to see? I mean, the astounding number of bones is unheard of, I gather, from just in one place like this, in Africa, certainly?
BECCA PEIXOTTO: Absolutely.
We excavated an area that was less than a meter square and about 15 centimeters deep, and from that area, we got more than 1,000 individual fossil specimens. And the density of that assemblage is really dramatic and it’s really unusual in fossil sites anywhere.
JEFFREY BROWN: You — we were talking about the small skull, right? You held the skull?
BECCA PEIXOTTO: I did, yes.
JEFFREY BROWN: What was that like?
BECCA PEIXOTTO: Nerve-racking.
JEFFREY BROWN: You’re taking a deep breath as you say it, right, a big sigh?
BECCA PEIXOTTO: Yes. Yes. It was nerve-racking to be there when the skull was coming out of the ground, coming out of the soil, and very gently trying to place it into some packaging to bring it to the surface without it falling apart, because these fossils are so fragile, particularly when they are first excavated.
I take a deep breath now because I think I held my breath the whole time we were working on the skull.
JEFFREY BROWN: You have a sense of the age of what you were holding, right?
BECCA PEIXOTTO: Yes, definitely, and the uniqueness of it, that here we were with all of these fossil specimens and were coming out with a very large fragment of a skull, which helps build a picture of what this creature was.
JEFFREY BROWN: Well, so, Jamie Shreeve, when you try to think of the importance of this finding, you were saying we still have to learn a lot more to see how it fits into our own evolution, but how would you gauge the importance right now?
JAMIE SHREEVE: Well, I think it’s arguably, you know, one of the most important finds in the last 50 years since Lucy.
And the reason for that is because we do have so much of it. Most of the time, when you find a new hominid fossil, you find a jaw, or a skull or a leg bone. Here, we found 1,500 bones. So you actually know a great deal about this creature that you couldn’t possibly know from just a fragment.
So, there will be a lot of analysis still to come. And the date is extremely important going forward to knowing how this fits. But it seems to be something that is near the beginning to have the Homo lineage, so it may help us inform this sort of black box of how our genus evolved from this more primitive form called Australopithecus.
JEFFREY BROWN: And, very briefly, I understand there are thought to be many, many more bones left in the cave, right, so there is a lot more to do.
JAMIE SHREEVE: Yes, it is littered with bones, if I’m not mistaken, right?
BECCA PEIXOTTO: It certainly is.
We went back a second time for another round of excavation in March of 2014, and recovered a couple hundred more fossil specimens. And we were able to recover some fossils that we were hoping to get, but we certainly did not exhaust the fossil supply in that chamber.
JEFFREY BROWN: All right, amazing.
Becca Peixotto and Jamie Shreeve, thank you so much.
JAMIE SHREEVE: Thank you.
BECCA PEIXOTTO: Thank you.
GWEN IFILL: It is amazing.
The program “Dawn of Humanity” is streaming right now on PBS.org. And it will air next week on “NOVA.”
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