Professor Lee Berger kisses the skull of a Homo Naledi , a newly-discovered human ancestor, during the unveiling of the discovery Sept. 10 in Maropeng.

Professor Lee Berger kisses the skull of a Homo Naledi , a newly-discovered human ancestor, during the unveiling of the discovery Sept. 10 in Maropeng.

Deep in a South African cave, scientists have made an astonishing discovery that could be millions of years old: the skeletons of at least 15 individuals, sharing many human characteristics. Experts say it’s evidence of a new species of human ancestor: “Homo naledi.” This find may be the most significant of its kind in half a century, helping to point us to the origins of genus Homo. But there’s a lot left to uncover: the age of the bones, how and why they were deposited in the cave, and how they fit in to the human family tree. We look at Homo naledi and a new piece of the evolution puzzle.

Guests

  • Jamie Shreeve Executive editor for science, National Geographic magazine; author of the October cover story for National Geographic magazine
  • Rick Potts Paleoanthropologist; director of the Smithsonian’s Human Origins Program; curator of anthropology, the National Museum of Natural History
  • Becca Peixotto Archaeologist; Ph.D. student, department of anthropology at American University; one of the primary excavators on the team that collected the fossils
  • John Hawks Paleoanthropologist, University of Wisconsin-Madison; senior author of the paper describing the new species

Q&A: What We Know (And Don't) About Homo Naledi

Q&A: What We Know (And Don't) About Homo Naledi - The Diane Rehm Show

Scientists from the University of the Witwatersrand, National Geographic Society and eLife answer questions about the newly-discovered, human-like species.

Watch: How Scientists Discovered Homo Naledi

Paleoanthropologist and National Geographic Explorer-in-Residence Lee Berger led a team of scientists in comparing the newly-discovered Homo Naledi fossils with those of other early hominins. (Video courtesy of National Geographic).

 

Photos: A New Human-Like Species

Transcript

  • 10:06:53

    MS. DIANE REHMThanks for joining us. I'm Diane Rehm. The newly discovered human ancestor, homo naledi, has teeth, hands and feet reminiscent of our own, but smaller brains, shorter frames and a host of other differences from modern man. Where the species fits into our evolutionary history is up for debate. Here to talk about what homo naledi could mean for our understanding of human origins: Jamie Shreeve of National Geographic magazine, Becca Peixotto of American University -- she's a primary excavator on the team that collected the fossils -- and Rick Potts, director of the Smithsonian's Human Origins Program.

  • 10:07:43

    MS. DIANE REHMOn the line from South Africa, John Hawks of the University of Wisconsin at Madison and senior author of the paper describing the new species. I know many of you will want to join the conversation. Give us a call at 800-433-8850. Send an email to drshow@wamu.org, follow us on Facebook or send us a tweet. Welcome and congratulations to all of you.

  • 10:08:17

    MR. RICK POTTSThank you very much, Diane. Great to be here.

  • 10:08:18

    MS. BECCA PEIXOTTOThank you, Diane.

  • 10:08:19

    MR. JAMIE SHREEVEThank you very much, Diane.

  • 10:08:21

    REHMJamie Shreeve, I'll start with you. Give us a little background on this. I gather it goes back to 2013.

  • 10:08:31

    SHREEVEThat's right.

  • 10:08:32

    REHMWhat was going on then?

  • 10:08:34

    SHREEVEWell, a couple of cavers in South Africa, in a system -- looking in a system called Rising Star -- they were just exploring, recreational cavers -- when they encountered at the top of a prominence called the Dragon's Back, about 100 yards into the dark of this cave, an opening -- a very narrow opening, about 8 inches wide. And Steve Tucker, one of the cavers, took one step down and then took another step down and then took another step down and it just kept going. And it was a chute that about 40 feet down emptied into another chamber. And that had another chamber next to it and it was littered with hominine bones -- bones of an early ancestor of some kind.

  • 10:09:21

    SHREEVEThis is a remarkable discovery. They knew it was strange -- you don't find human bones lying around in a cave 100 yards into the dark. And they contacted a paleoanthropologist named Lee Berger who had told cavers to be on the lookout for this sort of thing. Lee immediately saw that this was something extraordinary and mounted an expedition that National Geographic helped support to get into the cave and start excavating the bones. And I would say, what happened next, I might turn to Becca just because she was a part of it.

  • 10:09:55

    REHMIndeed. And, Becca, how did you become a part of this?

  • 10:10:02

    PEIXOTTOLee Berger put an ad out on Facebook, so it was a social media call for archeologists who had caving and climbing experience and were good excavators. And I felt like I met that combination of skills so I sent off my CV. And Just a couple weeks after interviewing over Skype, I was on a plane to South Africa, meeting the five other women who were chosen -- five other archeologists who were chosen to excavate these fossils.

  • 10:10:29

    REHMAnd, in part, you were chosen because...

  • 10:10:33

    PEIXOTTOLee was looking for folks who could fit through the chute, who could manage to get through this 18-centimeter gap that's vertical -- it's a climb down. So not only did we have to be qualified archeologists and good excavators, we had to quite literally fit in the cave.

  • 10:10:51

    REHMFit in the cave.

  • 10:10:53

    PEIXOTTOYeah.

  • 10:10:53

    REHMAnd you had to be really, really tiny to get into that cave. Tell us what it was like to really get in there.

  • 10:11:07

    PEIXOTTOThe chute itself is very jagged, it's not a smooth 18-centimeter gap. It's about 12 meters long, the chute itself, and there are teeth of rock that stick out in amongst it. And so, as you're climbing down this very narrow space, you're looking out for places to put your hands and your feet and trying to figure out how to squeeze your way around. It's not a straight line going down there. It's quite complicated.

  • 10:11:33

    REHMI gather you had never suffered claustrophobia.

  • 10:11:38

    PEIXOTTONot too often.

  • 10:11:41

    REHMNot too often. But, I mean, that is pretty narrow going isn't it?

  • 10:11:47

    PEIXOTTOIt is narrow going. And the caving helmets we all were wearing were all about the same size and there's a spot in the chute where there's only one way your helmet's going to go through, so you have to make sure you turn your head the right direction at the right time.

  • 10:12:01

    REHMWow. I would have been very frightened. Did fear enter your brain?

  • 10:12:13

    PEIXOTTOFor the caving part, I knew that we had a really good support system and I knew that safety was paramount for the expedition. We had Rick and Steve and other members of their local caving society there providing support for us. And so I knew that if there was something that went wrong, that we would -- we wouldn't be alone down in the cave.

  • 10:12:35

    REHMSo when you got down in the cave, what did you see?

  • 10:12:43

    PEIXOTTOAs you come out of the chute, there's an opening where we would take off our shoes so that we would walk barefoot into the final fossil chamber. There's a narrow slot that you turn sideways to walk through for a few feet and then it opens up. And the floor of the fossil chamber, the Dinaledi Chamber, was just covered in fossils. And, myself, when I walked in there the first time, you know, you could see a few fossils sitting on the surface. And as my eyes adjusted to the light and to the color of the sediment and the color of the cave and the color of the fossils, more and more just appeared on the surface.

  • 10:13:18

    PEIXOTTOAnd as we were cleaning the surface, we'd think we'd cleared a space of fossils and then you'd turn your head and look back to it and then there's more there. It's just a matter of getting used to seeing them in that sediment.

  • 10:13:29

    REHMWhat did they look like?

  • 10:13:32

    PEIXOTTOSome of the ones that were broken are whitish on the ends, so that makes them stand out a little more under our headlamps. The others are various shades of brown, stained by the sediment and by the process of fossilization. Some of them look like bones -- you could recognize teeth, you could recognize other parts of bones, and some of them, as we cleared the sediment away, then you could realize what skeletal element they were.

  • 10:14:01

    REHMWas there an actual skull that you came across?

  • 10:14:06

    PEIXOTTOThere was. It was fragmentary, so it wasn't a whole skull sitting there but there was. And that took us several days to excavate.

  • 10:14:16

    REHMAnd to you, John Hawks, in Johannesburg, tell me what those bones say to you.

  • 10:14:27

    MR. JOHN HAWKSThanks, Diane. You know, I think that everybody should appreciate that when we find any fossil hominine bone in a cave or anywhere, you know, it's hugely significant to us. You know, the evidence of our direct ancestry is so rare that, you know, everything -- it justifies mounting a big effort to recover. And in this case, we really thought that we were going to encounter probably part of one skeleton in this cave and that would be a huge discovery for us. Because you think of very famous fossils, like Lucy -- Lucy is a partial skeleton, she's about 40 percent complete. That's enormous evidence about the biology of an extinct hominine species.

  • 10:15:09

    MR. JOHN HAWKSSo the bones in the Dinaledi Chamber that we have, you know, subsequently named as a new species, homo naledi, they are more than 1,500 pieces of bone. They assemble into parts of at least 15 skeletons. We have the entire anatomy of the body represented, multiple times. We have, you know, 190 teeth. So it's a sample that is really unparalleled especially at this time, in the African fossil record, when, you know -- we have a couple of large assemblies in Europe like this, that are very late in our evolutionary history -- for this kind of primitive hominine in Africa, it is a unique sample. So, when you ask, what is it telling me? This sample is like shouting to me. It's like, here's our biology. Please, please, tell everyone.

  • 10:16:04

    REHMJohn Hawks, you sound pretty excited about the whole thing.

  • 10:16:10

    HAWKSYou know, it is a life-changing event, I mean, for everyone that's involved in it and it's been such a privilege. We have a team of more than 60 scientists around the world who have been engaged in analyzing the bones that Becca and the others brought out of the chamber. And the, you know, the scope of the work ahead of us is enormous. This is the sort of thing that the description of one skeleton takes teams years to accomplish. We have now published our description of this species and, of course, we have many, many years yet ahead of us. We are, you know, we are just thrilled to be able to share it now with the whole world.

  • 10:16:51

    REHMIndeed. And to you, Rick Potts. So are there definite similarities between homo naledi and us?

  • 10:17:06

    POTTSYes. Yes. Well, first of all, I want to also emphasize how awesome this discovery is and the process of bringing these bones to the light of day, to the surface, is heroic. It's just -- it's fantastic, it's great. And yet, at the same time, there are so many interesting questions there about how old the material is, how old the skeletons are, how they got into the cave. But there's no doubt in my mind that this is a new species, that this is something we've never seen before. And it combines traits that characterize earlier species, older species in our family tree, so to speak, our evolutionary tree, with traits that look like us, like later species, including homo sapiens, our species.

  • 10:17:56

    REHMRick Potts, he's a paleoanthropologist, director of the Smithsonian's Human Origins Program. Short break here. We'll be right back.

  • 10:20:02

    REHMAnd welcome back. We're talking about the astonishing discovery made in a South African cave of skeletons that could be millions of years old. Here in the studio, Jamie Shreeve, he's at National Geographic magazine as executive editor for science. Becca Peixotto is an archaeologist, Ph.D. student at American University, one of the primary excavators on the team that collected the fossils. Rick Potts is an anthropologist. He is curator of anthropology at the National Museum of Natural History. And joining us by phone from Johannesburg, South Africa, John Hawks. He's also a paleoanthropologist at the University of Wisconsin-Madison and senior author of the paper describing this new species.

  • 10:21:20

    REHMOne of these first questions that we've gotten from a listener in Boston, Alex. He says: How did these bodies get into this cave? And, Rick, that's what everybody wants to know.

  • 10:21:39

    POTTSIt's one of the great mysteries of this discovery. It's extraordinary, 15 individuals. From what I understand so far about the discovery, that there are no cultural artifacts associated with the bones so far. Usually when we think of a burial, we think of it in symbolic terms of an act, a gesture of respect, a ritual, where bones are actually -- bodies are buried. And, indeed, these bones may have been buried originally through natural processes, but there's nothing to indicate something symbolic -- a symbolic burial.

  • 10:22:20

    POTTSAnd so the question is, in my mind, is this disposal of remains? And I think that the papers that have been published so far are very careful in talking about the disposal of remains. But how did they get so deep into a cave? That's one of the big questions.

  • 10:22:37

    REHMWell, John Hawks, on that very issue, can't we assume that the entire landscape has changed dramatically since those bodies were buried. Perhaps it was not even a cave at the time. Assuming plate tectonics have done what they normally do, can't we assume that perhaps they were on the surface rather than in a cave?

  • 10:23:17

    HAWKSWell, we know that the bodies haven't been moved very far and that's because we have articulated hands and feet, the kinds of things that, if the bodies had been exposed or had been disturbed, they would rapidly disarticulate -- you'd never find those things together. So we know that these bodies got into this chamber at some point and, when they did, they were probably whole. We know that the cave could very well have changed over time. And one of the big questions that we have on our team right now is, how difficult was it in the past to get to the entrance to this chamber?

  • 10:23:53

    HAWKSThe chamber, itself, we can tell from the sediments inside of it, has been quite isolated from nearby chambers in the cave and we can tell that it has never been open to the outside.

  • 10:24:03

    REHMHmm.

  • 10:24:04

    HAWKSWe don't have the sand grains, the gravel, the organic stuff that would have fallen in if it had been exposed directly. So we know that this cave was not accessible to other animals, you would find their bodies in it. We know that it was probably -- it had a dark entrance to it. So probably homo naledi was, you know, doing something a little bit special when they got to the entrance of this. But what we don't know is how difficult it was. It might very well have been much easier than it is for our current team. But how difficult it was is one of those big factors as to understanding how homo naledi could have transported bodies to this place.

  • 10:24:46

    REHMBecca Peixotto, as an archeologist and Ph.D. student here at American University, all this has got to be just over-the-top exciting for you.

  • 10:25:03

    PEIXOTTOIt certainly is. It certainly is. It -- there are so many exciting things about this project, from the find itself to the way that the excavation was conducted, the way that the excavators and the scientists that did the analysis were found, the emphasis on incorporating early-career scientists and early-career folks into the project from the beginning...

  • 10:25:27

    REHMHmm.

  • 10:25:28

    PEIXOTTO...that stuff's all very exciting. And just all of the questions that these fossils raise is also very exciting. There's so much more for us to learn...

  • 10:25:39

    REHMOf course.

  • 10:25:39

    PEIXOTTO...and we need to go and look in places that we don't -- we wouldn't normally think to look, to find answers to our questions.

  • 10:25:47

    REHMAnd here's an email from Richard in Tallahassee, Fla. He wants to know, is there any evidence of the use of fire? That is, had this species mastered control of fire to explore these caves? Does it make sense for anyone, anything to navigate these caves in total darkness? Jamie Shreeve.

  • 10:26:18

    SHREEVEWell, to answer that last question first, no. I don't think you can navigate these caves in darkness. Becca would probably support me on that. So if the entrance to the cave was similar than it is -- as it is today, or even had some amount of darkness that had to be crossed, it does bring up the question, how were these very tiny-brained creatures going about negotiating in the dark? It brings up the possibility that they were using fire to light their way.

  • 10:26:51

    REHMHmm.

  • 10:26:52

    SHREEVEThough, as far as I know, there is no evidence that they did so. There's no sign of charred side to the cave or anything like that. But -- and this is a case for Sherlock Holmes.

  • 10:27:03

    REHMYeah.

  • 10:27:04

    SHREEVEI mean, this is not something that's going to be resolved that easily. And it's just circumstantial, but how else could they have gotten in there?

  • 10:27:10

    REHMHow do you know that these brains were so tiny, and how tiny?

  • 10:27:17

    SHREEVEWe know that because we have skulls of both females and males and we can measure the endocranial -- I should say, they can, I'm not part of the team, I'm just a journalist -- but they have done a good job at estimating the volume of the brain of both the females and the males. I believe the male's is about 560 ccs, which is less than half the volume of a homo sapien's brain, like ours.

  • 10:27:46

    REHMLess than half. Rick.

  • 10:27:48

    POTTSYeah, that's right. At the same time, we've -- over the last 10 to 15 years, we've become aware that the earliest member that would be assigned to the genus homo -- in other words, our evolutionary group -- had started out with rather small brains. And sometimes small brains express themselves in particular environmental situations -- for example, if the group was particularly isolated. There's a famous example of that from island, Southeast Asia, known as the Hobbit of human evolution, homo floresiensis, which is much late -- very quite late in time. And so what -- the brain size is not necessarily a clear indication of its age...

  • 10:28:37

    REHMHmm.

  • 10:28:38

    POTTS...or necessarily that it is something other than the genus homo, our evolutionary group. I think that's pretty secure, that homo naledi was part of our evolutionary group.

  • 10:28:49

    REHMSo, John Hawks, how large would you estimate the brain of the species that has now been discovered?

  • 10:29:02

    HAWKSWell, we're talking about a brain that's about a third the size of a human brain. The female's about 460, male's about 560 milliliters. It's comparable to the brains of earlier hominines that we call australopithecus. It is one of the features that we hesitate, you know, we say, wow, homo -- it looks like it's homo in the shape of its skull, it's homo in its feet -- they're very modern looking -- you know, homo in its hands. But we look at that brain, we look at the pelvis, we look at the shoulders, very curved fingers, it's one of those features that strikes us as being very primitive. And therefore, you know, makes it a bit more difficult to say exactly where this species fits on our family tree.

  • 10:29:45

    HAWKSIt's most comparable to species that we regard as being very early members of our genus -- species like homo habilis, early homo erectus. But that's sort of just a, you know, the overall picture. When you look at different features in detail, they're each telling you different stories. And that's one of the exciting things about finding a complete representation of the anatomy. Because we're used to dealing with a skull, a jawbone, some teeth -- we're used to dealing with these fragments. And we have a pretty good picture, we thought, of how fragments go together.

  • 10:30:22

    HAWKSBut once you start looking at the rest of the skeleton, you start to realize things don't always have to go together the way that you anticipated. And if they don't, it's a signature of the way that different members of the human family are adapting to their past environments. For homo naledi, the cool thing is that we don't know yet what that past environment was because we have no idea how old it is. We can -- we can -- yeah, go ahead.

  • 10:30:50

    REHMWe have no idea, Rick Potts, how old the cave itself is, do we?

  • 10:30:56

    POTTSThat's right. Well, the researchers -- the research team suggests, I think, largely on the basis of how these bones look, how the skeletons look, that the cave may have been there going back to perhaps two to three million years before the present. And one of the things that's interesting to me, with all the different fields of science that are involved in this kind of work, it's really pretty amazing that you can actually look -- that there are these drip stones or flow stones, dissolved calcite that occur in the caves -- and Becca could perhaps talk about this a bit more -- but my understanding is that the calcite doesn't cover the bones, maybe some of them.

  • 10:31:41

    REHMHmm.

  • 10:31:41

    POTTSBut if the bones had been in the cave for a long time, that long...

  • 10:31:45

    REHMWhy wouldn't they?

  • 10:31:45

    POTTS...why wouldn't they be covered with the kinds of stuff...

  • 10:31:46

    REHMYeah.

  • 10:31:48

    POTTS...you usually expect in caves and that you see in this case.

  • 10:31:50

    REHMSo what do you have, sort of stalactites and stalagmites?

  • 10:31:57

    PEIXOTTOThe cave -- the whole Rising Star system has absolutely amazing cave formations. There are stalactites and stalagmites, like you'd think of. There are these very fine little formations on some of the ceilings that look like little starbursts and, when you shine your headlamp up on them, they kind of sparkle.

  • 10:32:16

    REHMHmm.

  • 10:32:17

    PEIXOTTOIt's a really beautiful cave. And in the Dinaledi Chamber, when I sit on the floor of the chamber and look up at the ceiling that's several meters above, you can just see these enormous stalactites and other kinds of cave formations hanging down from the ceiling and it's really, really beautiful.

  • 10:32:35

    REHMCould you stand tall in that cave?

  • 10:32:39

    PEIXOTTOIn parts of it, yes.

  • 10:32:40

    REHMIn parts of it.

  • 10:32:41

    PEIXOTTOIn parts of it. Unfortunately, the part where we were working most often, there's a shelf of rock -- a fin of rock that comes out above where we were working. So most of the time, when we were working, we couldn't stand up. But if you stepped away from that a bit, you certainly can.

  • 10:32:58

    REHMHow many men, how many women in that cave? Do we know?

  • 10:33:04

    POTTSWell, it's a mixture.

  • 10:33:05

    HAWKSAmong the bodies?

  • 10:33:06

    PEIXOTTOYeah.

  • 10:33:07

    REHMSorry, John Hawks.

  • 10:33:08

    HAWKSNo. No problem. If you're asking about the bodies...

  • 10:33:11

    REHMYeah.

  • 10:33:12

    HAWKSWe don't know precisely. We know that we have at least eight children of different ages and at least six adults. One is a little difficult to tell if it's an older adolescent or a younger adult. We know that we have some females and some males but we don't know the precise numbers.

  • 10:33:29

    REHMInteresting. And you're listening to "The Diane Rehm Show." And it's time to open the phones. People are clearly very interested in this subject. Let's go first to Paducah, Ky., and to Jay. You're on the air.

  • 10:33:52

    JAYThank you very much.

  • 10:33:53

    REHMSure.

  • 10:33:53

    JAYGood morning. One of the questions that I had, is you talked about these cave explorers, the folks that discovered the bones. And one of the first things that it seemed like they did was they contacted an expert on this. My question, I guess, is -- as far as the legal ramifications and the legal issues associated with this -- first, is there some requirement that these folks would have had to contact law enforcement? All of a sudden, you walk in a cave, you discover all these bone (word?)

  • 10:34:20

    JAYDo you contact law enforcement? Two, is there some requirement that you contact some sort of antiquities agency or organization in South Africa about this discovery. And, three, what do you have to do once you make this discovery? Do you have to go through this incredible process? What happens to the bones during the course of this excavation?

  • 10:34:40

    REHMOkay. You've got lots of questions there. Rick, talk about the legal factors first.

  • 10:34:47

    POTTSWell, in every place around the world that I've ever excavated, which has mainly been focused in East Africa as well as China and a number of other countries, it's always important, of course, first to contact the landowner. Or sometimes the landowner contacts the scientists. And, of course, there are always laws governing antiquities in all countries. And it's the responsibility of the archeologists to make sure that they are abiding by the laws. And one thing I do know is that Dr. Lee Berger, the director of the Rising Star project, has a terrific relationship with all of the authorities and landowners involved in this kind of work.

  • 10:35:32

    REHMBut does that mean, John Hawks, that you have to go to the South African government before you begin to delve? And then once you delve and you discover, then what happens to those bones? Whose property are they?

  • 10:35:56

    HAWKSWell, in South Africa, the South Africa Heritage Research Agency is the governing body over this. They're a governmental organization. We're digging at a site that's in the -- that's in a UNESCO World Heritage Site, the Cradle of Humankind World Heritage Site. So we also have regulations associated with the World Heritage that we have to comply with. It's a permitted process. It is for any kind of resource, underground or culture resource work in South Africa. And so there is a permit holder. In this case, it's Lee Berger. Everything that we do is conditioned on conserving the site and making sure that the bones are secure where they are.

  • 10:36:37

    HAWKSThe bones, themselves, are the property of the people of South Africa. And once they're excavated, they're curated at the University of Witwatersrand. They're held in a big vault alongside of many other famous bones. I do want to say, the conservation part of this is an important part of our story. Many people want to know, why didn't you expand the hole so that people could go in there more easily? The reason why is that we're working with local people, the local cavers and the heritage authorities to make sure that we're conserving the contours of these caves as they are, in their natural state.

  • 10:37:09

    HAWKSYou know, we have skilled teams who can get down into difficult places and do this work. And so, as long as we can do that, it's our priority to make sure that the bones are safe. And that's why we immediately responded when they were found. But it's also our priority to make sure that they remain conserved and their environment remain conserved. So, you know, a lot of people don't think about the management sort of consequences...

  • 10:37:32

    REHMRight.

  • 10:37:33

    HAWKS...that come with a major site like this.

  • 10:37:35

    REHMAll right. John Hawks, paleoanthropologist at the University of Wisconsin-Madison, thank you so much for joining us. And, short break, we'll be right back.

  • 10:40:02

    REHMAnd welcome back. We're going to go right back to the phones. I know many of you have questions. We'll try to get to as many as possible. To Gleen in Manassas, Virginia. You're on the air.

  • 10:40:21

    GLEENYes, good morning, Diane.

  • 10:40:22

    REHMHi there.

  • 10:40:23

    GLEENWell, I'm glad that you're back on the radio.

  • 10:40:26

    REHMThank you so much.

  • 10:40:28

    GLEENI enjoy your show so much. My question, I can be taken off, but I think maybe you've either answered it or come close. My question was, this new discovery. Does it fall between the homo erectus and the Australopithecus africanus? That during your discussion, I gather maybe it could be a parallel development or something. Anyway, when you start talking about the size of the brain, you gave me the impression that this brain was smaller.

  • 10:41:02

    REHMYeah.

  • 10:41:02

    GLEENThan the African -- the Australopithecus africanus. And I was wondering, is it possible now they might do some DNA testing? Is that possible?

  • 10:41:15

    REHMWhat a good question. Rick Potts.

  • 10:41:17

    POTTSRight. Yeah. Well, this is indeed a combination of brain size and the shape of the bones of the hand and feet and of the whole body that is unlike anything that we have seen before. One of the things that the scientific team has shown is that the variation, the amount of the range of variation in the bones is quite small. In other words, if you measure the bones, if you look at the different characteristics of the bones, and you take any two individuals, or any 15 individuals from the present day human population, the variation is very small in the new finds.

  • 10:41:59

    POTTSAnd that suggests to me that we may be dealing with an isolated group. They're -- the combination of features looked like those of earlier species combined with later species, but could they have persisted for a long period of time, kind of like in their own lost world? A world of isolation that then they may not be two to three million years old, as suggested from the bones, but might actually be, as the papers do indeed suggest, as one possibility, later than one million years, perhaps after the use of fire becomes known in the archaeological record? That would also help tie some of this information together.

  • 10:42:45

    REHMRyan, on Twitter, is asking what Homo Naledi features most resemble us as modern humans. We've talked about feet, hands, what else? Jamie.

  • 10:43:03

    SHREEVEWell, the interesting thing is that the parts of the anatomy that are interacting most with the environment are the ones that are most like us. Hands, feet, long leg bones, probably indicating a creature with a striding gait, very much like ours. As you get more and more interior in the body, it becomes more and more primitive. Now, what does that mean? I don't know. It's one of the many mysteries involved, but the shape of the skull, as I understand it too, is very much similar to a more modern skull. Though its size is the primitive part, so...

  • 10:43:44

    POTTSYeah, I would agree with everything Jamie said. I would add, though, that one part of the body that interacts a lot with the environment are the fingers.

  • 10:43:54

    SHREEVERight. Absolutely.

  • 10:43:54

    POTTSAnd the fingers are long and curved.

  • 10:43:57

    REHMReally?

  • 10:43:57

    POTTSSuggesting some -- a creature that part of our own evolutionary tree that was actually climbing trees, climbing physical trees. And so, that is really interesting. You have a hand that's, overall, shaped like ours, but with a hand of a tree climber. And so, again, this is a little bit of a unusual aspect to these finds.

  • 10:44:19

    REHMAnd an email from Frank in Gainesville, Florida. Has anyone considered the remains in the cave are there because they are part of a mass execution? What do you think, Becca?

  • 10:44:38

    PEIXOTTOThe -- when the geologists have looked at the caves and when the researchers have looked at the caves, they've gone through a lot of different possibilities in looking at this. Is this a mass catastrophe? Was there a sinkhole that opened up and this group of creatures fell in? Did they wander in? Did they get drug in by predators? Those kinds of things. And one by one, those kinds of possibilities have been sort of ticked off the list. There are teeth marks on the fossils, suggesting that they were drug in by a predator, that there's no indication of predation.

  • 10:45:11

    PEIXOTTOThe geology does not appear to indicate any kind of other opening in the ceiling of this cave through which these creatures could have fallen through. And so, we're left, at this point, with the possibility of deliberate body disposal and what happened prior to the bodies becoming no longer alive, we don't know and we don't have -- we haven't really looked at that yet.

  • 10:45:36

    REHMBut when did burial become part of the human process? Rick?

  • 10:45:43

    POTTSRight. This is a big question, both about the burial, as well as the fire. With regard to fire, the earliest known evidence of hearths, of campfires, goes back to about 800,000 years ago. Still a long time ago. And in, actually, in a cave close by, there is evidence reported last year about a million years old. And then, the oldest known symbolic burials are about 100,000 years old in our own species. And both our species as well as our evolutionary cousins, Neanderthals, buried their dead. But relatively recently.

  • 10:46:24

    REHMAnd a lot of people are asking the same question that Michael is asking. Do we know for sure that they did not enter the cave alive?

  • 10:46:42

    POTTSI don't think we know anything for sure. That sure, but it seems highly unlikely that 15, at least 15 individuals, including, by the way, babies, infants. I've seen these bones. There are vertebrates the size of thimbles included in this collection. And elderly people, as well. The notion that they would be somehow sort of lured into or called upon to descend into a cave, crawl down a little chute that's eight inches wide and leave themselves there on purpose seems easily, more easily eliminated than the one that the one hypothesis that they're going with.

  • 10:47:25

    REHMAll right. And to Grand Rapids, Michigan. Hi there, Brian. You're on the air.

  • 10:47:32

    BRIANGood day, Diane.

  • 10:47:34

    REHMHi.

  • 10:47:34

    BRIANSo glad to have you back.

  • 10:47:36

    REHMThank you.

  • 10:47:36

    BRIANMy question is from the teeth, were they able to determine what type of diet they may have been eating at the time? And the second question I have is did they have a tail?

  • 10:47:53

    REHMDiet.

  • 10:47:54

    PEIXOTTOI think the research on the teeth is ongoing. The initial analysis of these fossils was really focused on describing them and determining whether or not this was a new species. And the analysis, of course, has shown that it is. And evidence for diet and further studies -- that's just ongoing.

  • 10:48:15

    REHMSurely, nobody's talking about a tail.

  • 10:48:18

    SHREEVENo, there's no evidence of a tail.

  • 10:48:20

    REHMOkay.

  • 10:48:20

    SHREEVEThere hasn't been a tail, at any point, in our own direct evolutionary tree.

  • 10:48:26

    REHMAll right.

  • 10:48:26

    SHREEVEBut it connects with much earlier, earlier ancestors.

  • 10:48:29

    REHMLet's go to Orlando, Florida. Edward, thanks for calling.

  • 10:48:35

    EDWARDWell, good morning.

  • 10:48:36

    REHMHi.

  • 10:48:36

    EDWARDAnd your guests are really asking some terrific questions. I'm excited. I'm going to have to follow up on this. I'm a retired archaeologist.

  • 10:48:45

    REHMGood. Good.

  • 10:48:48

    EDWARDBut that's enough on me. I only have one question, because it seems like a lot of people need to ask more. And I'm trying to keep the proper academic decorum here with my excitement. How many teeth have you found? Is it 28 or 32?

  • 10:49:04

    REHMDo we know?

  • 10:49:06

    SHREEVEWell, the human jaw and the jaw of, the jaws of upper and lower of all humans and human ancestors have 32 teeth. All the way back to the third molars, the molars that come in. And we share that characteristic with other higher primates. With other fossil apes and with modern apes, and so, and also with the monkeys that come from the old world. This is part of our primate, our very deep primate evolutionary heritage. 32 teeth.

  • 10:49:39

    REHMAll right. And to Norfolk, Virginia. Sandy, you're on the air. Go right ahead.

  • 10:49:46

    SANDYFirst of all, I have to say my little family loves you, Diane.

  • 10:49:49

    REHMThank you.

  • 10:49:51

    SANDYAnd your show. Now, my only question is, has, or could there be some connection between Pygmies in Africa and the Homo Naledi species?

  • 10:50:02

    SHREEVEWell, if I could take that one. I doubt very much that there's any direct connection. The Pygmies in Africa are a central African group, a popular, several populations of -- and they are Pygmies because they have adapted to a particular environment. That environment, as far as I know, was probably not existing at the time these creatures were alive. So, their stature size, really, has nothing to do with modern Pygmies.

  • 10:50:32

    REHMJamie Shreeve. He is the author of the cover story of National Geographic's October issue. And we have a question on that very point. A tweet from Matt who says, for this study authors, you could have had a cover at Nature or Science. Why did you choose an online, open access journal in which to publish? Jamie.

  • 10:51:11

    SHREEVEThat's a very good question. And, in fact, the authors did originally intend to publish their work in Nature, the journal Nature. The process of science publication, of a fossil like this, though, is immensely complicated. When you're doing just -- when you've found just one skull or something equivalent to that, it can take a long time to describe it and go back and forth with reviewers at a publication like Nature. In this case, we had 1500 bones. And as I understand it, I was not, of course, directly involved with the publication.

  • 10:51:49

    SHREEVEThe process of reviewing and revising the papers in the traditional sense that a science publication like Nature, was just too long and complex, given the team's desire to get this information out quickly. So, they chose, instead, to switch focus and put their papers in an online journal, E-Life, which is a very reputable new journal, founded by a Nobel Prize winner. They decided to put them there and get the information out more quickly.

  • 10:52:20

    REHMIsn't that kind of risky, however? Suppose that it turns out that these relics are less authentic, less valuable, less elderly than we think they are?

  • 10:52:38

    POTTSWell, I think that we have to realize that an enormous international scientific team has been involved in this study, and the authentication of these, of these remains. And so, there's no doubt in the scientific community, from the community of paleontologists who study fossil bones and archaeologists and geologists and so on. That these are very important remains.

  • 10:53:09

    REHMRick Potts is a paleoanthropologist. He is curator of anthropology at the National Museum of Natural History. And you're listening to The Diane Rehm Show. A number of people are asking, is there a way to get DNA from these bones? What do you think?

  • 10:53:38

    PEIXOTTOThat is something that the researchers have put off doing until the papers were published, until the fossils were described. Now that the fossils have been described, the process of extracting DNA, for example, from the teeth of these fossils, is a destructive process. You have to destroy a small part of it in order to do that. So now that the fossils have been described, now the analysis team will be looking at ways to extract that other information.

  • 10:54:10

    REHMAnd will the US scientists be working right along with South African scientists, Rick?

  • 10:54:15

    POTTSWell, indeed. And in fact, with regard to the DNA studies that will occur, one of the best labs in the world is in Germany, and so there will be labs in America, in Germany, South Africa, and many parts of the world.

  • 10:54:31

    REHMWait a minute. What you're saying is that these parts are going to be distributed to various labs.

  • 10:54:38

    POTTSNo, not necessarily. The parts will stay conserved in South Africa, but the destructive part, which will take maybe sacrifice a tooth to get at the fragments of DNA that may be preserved can be studied by multiple labs. And so, that way, the different labs can compare their results and look at the relationship of any existing, preserved DNA to the DNA...

  • 10:55:03

    REHMDescribe how that's done.

  • 10:55:05

    POTTSWell, how, what's done is that the tooth itself, for example, or maybe another part of a skeleton is ground up and it's -- through quite a complicated process that would be similar to getting DNA out of a bone of a modern human. That pieces of DNA can be gotten, and then it's amplified. In other words, it's replicated over and over and over again through a technique, a complicated technique called PCR. And that can -- through that process, the DNA code can be mapped and studied by a variety of labs.

  • 10:55:45

    REHMAnd how long would you think that process might last?

  • 10:55:50

    POTTSIt can take -- well, I have, actually, recent familiarity with bones from the Smithsonian, of a Neanderthal, or what we thought was a Neanderthal. Went to Germany for analysis and that analysis took about three months. We found out that the bone wasn't that of a Neanderthal.

  • 10:56:09

    REHMReally?

  • 10:56:09

    POTTSIt was actually a bone of a much later individual, modern human who was buried into layers that had included Neanderthal bones.

  • 10:56:20

    REHMAnd is that a possibility here?

  • 10:56:23

    POTTSWell, this is going to be one of the great parts of the detective work.

  • 10:56:26

    REHMYeah.

  • 10:56:27

    POTTSI mean, it really is a detective story.

  • 10:56:30

    REHMYeah.

  • 10:56:30

    POTTSA who done it. As well as a -- what exactly happened here and who is Homo Naledi? Who are these individuals? And DNA may help us.

  • 10:56:40

    REHMAnd one person says, with the world in religious turmoil, what significance does this discovery have for modern man or woman? Very briefly.

  • 10:56:56

    POTTSWell, very briefly. This is the story of all of us. It is a world that we live in, a world of division, that exists through not just religious or nationalistic boundaries. But for all the ways in which we think about one another. And to be able to study the common ancestry and relatives of all humankind is marvelous.

  • 10:57:18

    REHMGreat answer. Rick Potts, Becca Peixotto, Jamie Shreeve. He is the author of the October cover story for National Geographic Magazine. Thank you all so much.

  • 10:57:36

    POTTSThank you, Diane.

  • 10:57:37

    SHREEVEThank you.

  • 10:57:37

    PEIXOTTOThank you.

  • 10:57:37

    REHMAnd thanks for listening. I'm Diane Rehm.

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