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IRA FLATOW, host:

This is TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow.

Thirty years ago, in a remote part of Ethiopia, paleoanthropologist Donald Johanson discovered what was then the oldest skeleton of an upright-walking human ancestor, the famous Lucy skeleton.

Well, a lot has happened in the last 10 years. One thing, Lucy has a family. The newest member is the recently discovered Dikika baby, a three-year-old skeleton of the same species. And now our family tree appears to go back more than six million years as new fossil finds continue to fill in some of the gaps on that tree, answering some questions and raising others.

We spoke with Don Johanson and science writer Blake Edgar nearly 10 years ago when their book "From Lucy to Language" was first published. And the revised edition of the book is just out, updating with the last decade's worth of findings. And they're here with us today to bring us up-to-date on the ever-changing field of human origins.

And if you'd like to get in on the discussion, give us a call. Our number: 1-800-989-8255, 1-800-989-TALK. And as we did 10 years ago, actually, with pioneering work, SCIENCE FRIDAY actually put photographs on the Web site. It sounds strange that you had a photograph on a Web site, but in those days there weren't many. We put photographs on the Web site of fossil photos, and today we've got them up again. And if you go to sciencefriday.com, there are fossil photos of the newest findings on sciencefriday.com that you can watch along with us as we talk about them.

Let me introduce my guests. Donald Johanson is a co-author of "From Lucy to Language." It's out again, reissued by Simon & Schuster. He's founder and director of the Institute of Human Origins and the Virginia M. Ullman Chair in Human Origins at Arizona State University in Tempe. And he joins us today from KJZZ in Tempe. Welcome back to the program.

Dr. DONALD JOHANSON (Co-author, "From Lucy to Language"): Well, thanks, Ira. It's a pleasure to be back. You shouldn't have waited 10 years.

(Soundbite of laughter)

Dr. JOHANSON: So much has happened I don't know how we're going to cover everything.

FLATOW: We've got a while. Blake Edgar is a co-author with Dr. Johanson of "From Lucy to Language," and he is acquisitions editor in the Science Publishing Group at the University of California Press at Berkeley. And he joins us from the UC Berkeley campus. Welcome back to the program, Blake.

Mr. BLAKE EDGAR (Co-author, "From Lucy to Language"): Thank you, Ira. It's great to be back with you and Don, and from my alma mater no less.

(Soundbite of laughter)

FLATOW: Don, I understand you're just back in the country this week. You were working on something, something good I'm sure.

Dr. JOHANSON: Well, I am just back. I spent two weeks in South Africa, most of it fortunately was a little vacation, long overdue. But of course I was close to all those wonderful Australopithecus sites and had an opportunity to visit with my friend Ron Clarke, who has made a miraculous discovery.

It's been known for quite some time. It's highlighted in our revised edition now. It's probably the most complete - and we hear this a lot - but one of the most complete skeletons of Australopithecus ever found. It's buried deep within one of the caves known as Sterkfontein, and in 1994 Ron found the little ankle bone in a box of antelope bones. And he said, boy, this doesn't look like an antelope. This has got to be a human ancestor.

And he sent his collectors down into this huge cavern and found the exact spot on the wall where the bone had been broken decades ago. And during excavation now he has a complete skull, parts of the backbone, both of the legs, parts of the arms, and a hand which is curled almost as if it's in the death position. And I had a close-up look at this. It's an astonishing find, and it's probably going to turn out to be the oldest, most complete adult Australopithecus.

FLATOW: And where would we place this in relationship to Lucy?

Dr. JOHANSON: Well...

FLATOW: Living the same time?

Dr. JOHANSON: Well, pardon the pun. It's a bone of contention right now.

(Soundbite of laughter)

Dr. JOHANSON: I kind of think that it has affinities to Lucy's species, Australopithecus afarensis. It's been tentatively dated as well over three million years, and it may turn out that Lucy's species actually had migrated as far as Southern Africa at that time. Final diagnosis I think has to await full excavation of the specimen.

FLATOW: There's one other really recent finding that was too new to have made it into your book, and that is the Dikika baby. Tell us about her.

Dr. JOHANSON: Oh, the Dikika baby is just a - I mean who could have a better-looking baby than this?

This is a 3.3 million-year-old, virtually complete child skeleton. And what I mean by that, it was three years old when it died 3.3 million years ago. It has got the entire skull, meaning the brain case; the lower jaw is still attached to the skull. It's got most of the backbone, both shoulder blades, tiny little almost pea-sized kneecaps. It's got parts of arms and legs, and it is going to allow us for the very first time I think to really examine in great detail how a baby Lucy grew up to be an adult Lucy.

It is a female. It's often referred to as Lucy's baby. It's about a 100,000 years older, so it obviously couldn't be her baby, but it's a kind of baby that Lucy would have had. So it expands our understanding of Lucy's species, and there's no doubt that this belongs to afarensis, because in 1975 we did find the first baby skull not far from where Lucy was found, and it looks identical to this specimen.

FLATOW: And according to what I've seen and read about it, it has the hips and legs of a creature that would walk upright but the climbing ability of its ancestors.

Dr. JOHANSON: That's right. We don't have the - there's no pelvis preserved like there is in Lucy, but there is - there are two knee joints. And by looking at the details of how those bones articulate - our shinbone and our thighbone -it's beyond question that this creature went on the ground, was capable of upright walking just as we are.

But there are hints, very interesting aspects of particularly the shoulder blade - something that is almost unknown because it's really paper thin - but the aspects of that are very, very similar to a gorilla. And it suggests from the orientation of where our upper arm bone actually inserts into the shoulder that perhaps it could have really helped them climbing in the trees.

I think they were primarily bipeds on the ground, but why not climb in the trees at night for safety? Why not climb in the trees for fruit, the sort of food that their ancestors were eating? I think we're looking at a species in transition. We're looking at a mosaic set of anatomy very advanced towards us, in being bipedal in the knee and hip, but still retaining ancient ancestral characters in the upper part of the body.

FLATOW: Blake?

Mr. EDGAR: I can remember being here in Berkeley in 1983 at a symposium that Don's institute hosted about the question of how terrestrial or arboreal afarensis is, or was. And it's just interesting to have this specimen now reopen that debate, and we've already seen varying opinions as to whether it's going to close the debate or just provide a new angle on it.

But it's a fascinating specimen. It also reminds me the face and skull and the fact that you have an endocast - a cast of the brain from sandstone - reminds me of the Taung child that Raymond Dart found in the 1920s, which got a very different and much more negative reception but was really the first fossil to point us all toward Africa as the place to look for human ancestors.

FLATOW: On our Web site we have a photo from the book "From Lucy to Language," this revised edition by Donald Johanson and Blake Edgar. If you go to sciencefriday.com and you look at that first picture on the top left.

We have the honor of showing the seven-million-year-old Toumai man. Lucy is no longer the first family.

Dr. JOHANSON: Well, no. Lucy is certainly not the oldest. But the Toumai specimen, as it's sometimes called, was found in Chad, in north central Africa, in 2001. It's a very crushed and distorted skull. It's been estimated to be between six and seven million years.

And opinion is very divided on this. There are some people who think it was an ancestor to a gorilla. There are others who think it might have been an ancestor to the later apes. And the discoverer Michel Brunet and his team in Poitiers, France, think that it was an ancestor to later hominids.

So it's one of those provocative specimens I think about which we really need to know a lot more. Meaning, we need to find some more specimens of that age before we can ascertain whether it is a genuine hominid or an ancestor to later hominids. Because the bimolecular work is suggesting the split between the African apes, chimps and guerillas, and ourselves - humans - was something around five to seven million years ago. So this specimen may be in fact too old for the common ancestor or even an ancestor to hominids.

FLATOW: And then we have - moving closely to us, Blake, we have a bit younger than Toumai man is the millennium ancestor. Why was that such an important find?

Mr. EDGAR: Well, it's a very controversial find, and it was important because it - again, there are several finds now competing for earliest hominid, and it's one of them. You do have - it's mostly post-cranial although you have some dental fossils, but the most important ones are the two thighbones - the femurs. And they indicate that it was likely bipedal, but again this is a controversial point.

And there's been a lot of fractious discussion among and debate among the people involved - Brunet find with Tounai, and in this case with the millennium ancestor, Orrorin - Brigitte Senut and Martin Pickford - that it's interesting that as you get closer to this time period, this node when the human lineage and the chimp lineage come together, as Don was just describing, there seems to be a tendency to come up with not just new species but new genera of these ancestors. So there are lots of new names that we have to wrestle with and figure out how distinctive they really are. And it's going to be challenging to really tease out what were the real features of the earliest hominids other than bipedality, I think.

To me, it points to the fact that we need more ancient chimpanzees fossils as well as. The ape fossil records is really still a black hole. The issue of Nature that described the chimpanzee genome a couple of years ago also had a short paper about the first bona fide chimpanzee fossils from Kenya, and we need more finds like that.

FLATOW: Donald, we've got about a minute till the break, but are we beginning to fill in in these last 10 years a good picture of a straight lineage?

Dr. JOHANSON: Well, I think we're beginning to fill in the time period between say, three and four million years. The work we've continued to do at the site where Lucy was found at Hadar, the work that Meave Leakey has been doing in northern Kenya, is suggesting that there is a single lineage over at least a million years documented by these extraordinary fossils.

The site of Hadar, we have closed to 400 specimens of Lucy's species. And this is the most densely populated fossil species we know of, so it's beginning to reveal something about the tempo and the mode of human evolution.

FLATOW: Talking with Donald Johanson and Blake Edgar, co-authors of the new revised, updated and expanded "From Lucy to Language." It's a terrific book. If you're looking for a gift for the holidays this season, this is just a terrific coffee table book. And I'll tell you it's gorgeous book and a joy to read. And it's educational, believe it or not. Stay with us. We have to take a short break. We'll be right back to talk more about "From Lucy to Language" and take your phone calls. Don't go away. We'll be right back.

(Soundbite of music)

FLATOW: I'm Ira Flatow. This is TALK OF THE NATION: SCIENCE FRIDAY from NPR News.

(Soundbite of music)

FLATOW: We're talking this hour about the filling in the gaps in our human evolutionary tree with Don Johanson, co-author of the revised "From Lucy to Language." Also co-author Blake Edgar. Our number 1-800-989-8255.

How did you get such stunning photographs? I mean taking these pictures are just terrific. I mean the lighting, whatever. You know.

Dr. JOHANSON: That's right. I mean I'm so envious of the photographer. I wish I had the ability to do this. David Brill.

FLATOW: David Brill.

Dr. JOHANSON: Yeah. David Brill is a photographer based in Atlanta who I met way back in 1975. I'll never forget. I was in (unintelligible) in my camp and a light, low-flying aircraft came over my site in the middle of Ethiopia, and I knew it was a National Geographic photographer arriving. And I was late to pick him up, and I arrived, and he was sitting under an acacia bush with all of his equipment waiting for me. He really caught the bug. He really got terribly interested in the subject. And began to look at the kinds of photographs that were available and realized that there was really nothing out there. And David has dedicated his life to working on a method that would bring these fossils literally to life. They're almost three-dimensional.

FLATOW: Yeah. And they're just amazing photos.

Mr. EDGAR: I was just going to say I watched him work in nearly 20 years ago setting up the photograph that appeared on the front cover of the first edition of the book of (unintelligible) and it just take hours for him to get one image as he so meticulous in the use of mirrors to capture and light, highlight aspects of the anatomy.

FLATOW: We don't do them justice. We have some at our Web site at sciencefriday.com. You can see some of the photos but you have to really look at the book "From Lucy to Language."

Let's go to the phones 1-800-989-8255. Let's go to Robin in Boston. Hi, Robin.

ROBIN (Caller): Hi. How are you?

FLATOW: How are you?

ROBIN: Good. Hi, Don.

Dr. JOHANSON: Hi, Robin. How are you?

ROBIN: I'm good. I just want to say I'm a very big fan of you and Lucy and your book. And Ira's right about "From Lucy to Language," the pictures there are just crazy good.

Dr. JOHANSON: Thank you.

ROBIN: I have a question about the Dikika skeleton. You know, she's so gorgeous and she's so complete but it's too bad we don't have those pelvic bones. How certain can you be that everything was excavated?

FLATOW: Did you leave anything there?

Dr. JOHANSON: You know, that's a very good question because that's something that always haunts us, whether we've missed something in the field. I had the great opportunity to be invited by Dr. Zeresenay Alemseged. We call him Zeray. He was a post doc in fact with me here in Tempe, Arizona, at the institute, and made the discovery when he was a post doc at the Institute of Human Origins. And he invited me to come out to see the site, the Dikika site, which is just across a river from where Lucy was found. And I spent a month with him in the field excavating at the baby's site. And I can say that this was one of the most thorough and complete recovery operations I've ever seen.

He's been working at that site almost yearly for several years, extensively collecting all the lose soil, meticulously screening it through several different size mesh screens. I'm pretty darn sure that he has picked up every darn fragment of that skeleton that's out there. Maybe the pelvis is still buried inside the sandstone block that he's working on. But I can certainly attest that this was an extraordinary operation by really the first Ethiopian scientist to organize, lead, and make a major discovery on such an expedition in Ethiopia. He's extraordinarily...

ROBIN: I can quit worrying about it, then.

Dr. JOHANSON: What's that?

ROBIN: I can quit worrying about it, then.

Dr. JOHANSON: Yeah. I wouldn't worry about it. I think that Zeray has done a splendid job and has collected everything that was on the surface.

ROBIN: Thank you.

FLATOW: Good luck. Happy holiday season to you.

ROBIN: Thank you. You too.

FLATOW: 1-800-989-8255. There was a lot of interesting speculation recently, a controversial find about the Flores man. And there was a disagreement over whether this is a new species, or just a small homo sapiens, people called it the Hobbit. Where we stand on that, Blake? What's happening with it?

Mr. EDGAR: Well, talk about the contentious find. It's really interesting. I think the jury is still out as to whether it's a pathological specimen. Robert Martin, who's an expert on the primate brain evolution, has argued this case that perhaps it, the specimen that we have on the book, suffered from microcephaly. As we note in the book, it's a case where facts are stranger than fiction. Really unusual to have something so small, so recent in time, and not unusual to have a dwarf on an island. We know that from pygmy mammoths on the Channel Islands off the California Coast for example; or the opposite, having Komodo dragons, the largest lizards in Indonesia.

But the brain of this one is so small. It's really not significantly larger than the Dikika baby that we were describing earlier, but in an adult and something that overlap with modern humans. So I think more work needs to be done to investigate that. Martin, for example, says that if you shrunk down an average adult homo erectus, which had a brain of about - brain volume of a thousand cubic centimeters, to get something with a brain as small as that in the Flores hominid you'd end up with the individual that stood about a foot high and weighed five pounds. So that's some hobbit.

FLATOW: 1-800-989-8255 is the number. Let's go to the phones. Let's go to Sharon in Michigan. Hi, Sharon.

SHARON (Caller): Yes. Hi, Ira. How are you?

FLATOW: How are you? Go ahead.

SHARON: Good. First, I just want to comment. Dr. Johanson, what an amazing discovery with Lucy. 1992 was the first time I had the chance to see her when I was studying archaeology in Nairobi. I have to say, it gave me chills to see this specimen.

But my comment, or my question actually, for your panel is: With all these discoveries that we're seeing in the last 10 years, I was wondering if you guys thought that over the next 10 or 20 years that we might see some more discoveries that would really shake up our understanding of the evolution of hominids and/or they're dispersion throughout the world? And I'll take my comment off the air.

FLATOW: Okay. Thank you.

Dr. JOHANSON: You know. That's an excellent question, and certainly the specimen from Flores, Indonesia, is an important lesson to us. I agree with Blake that the jury is still out. I've not seen the specimen but I have held in my hand a cast of the skull. It looks astonishingly like a regular human skull that has been shrunk in size. And if this is the case, it challenges a lot of ideas of human brain growth. Because we've always thought that natural selection was selecting only for larger and larger brains, and here was a brain that was about the size of a Lucy brain that was 3.2 million years before.

I suspect there will be a lot of surprises out there. Journalists often ask me when I go to the field, what do you expect to find. And my answer always is the unexpected, because we're just looking at the tip of the iceberg, we've just scratched the surface. I think we're going to see a lot more species out there. I think we're going to find that hominids diversified into a whole series of environmental/ecological behavioral niches. And it's going to get more difficult to sort our ancestor-descendant relationships.

But that's really the charm, the excitement of doing this kind of science, to be in something in a science where you know a discovery can get you to think about things in a totally different way.

FLATOW: Do you ever find fossils from something that's not in your field, like maybe a dinosaur fossil, and you say, hey maybe I have to call Michael Novacek and ask him to come over and take a look at something like this?

Dr. JOHANSON: Well, if I found a dinosaur fossil, I would know that the deposits were older than 65 million years. And since humans didn't get here till, you know, five, six, or seven million years, I certainly would call Michael in to look at it. But we find tons, literally tons. If you were to go to the National Museum in Addis Ababa, you would walk into a huge room filled with literally tens of tons of fossils, and most of them would be elephants and rhinos, and hippopotamus, and monkeys, and giraffes, and antelopes and so on. Hominids are very rare in the landscape, and it's very rare to find them.

So the site of Hadar, where Lucy was found, where we have some 380 specimens or so, is an extraordinary site. It's the richest single place in all of Africa. That's why it's actually so important.

FLATOW: And what makes - what gives it that? What traits about where the finds are located?

Dr. JOHANSON: Yeah. That's an excellent question because when I was a novice in the early 1970 working in southern Ethiopia, the geological deposits were brought there by a large paleo river, so that animals would fall into that river and decay. And because of the power of the moving water they would be broke up and scattered, and sometimes you'll only find tiny fragments or isolated teeth. The site of Hadar is so important, as is Dikika, because it wasn't ancient lake. So it was a very low energy environment.

So a creature like Lucy, who probably died near the edge of the lake, fell into the lake, was floated out into the lake and eventually decayed. The skeleton, still hanging together with the ligaments, fell to the bottom and was covered slowly by sand and silt in clay; and slowly turned from organic material into a fossil-hard stone. So it is the depositional environment, it's the place where you die that - it makes the major difference between dying in a river and dying in a lake.

FLATOW: 1-800-989-8255. Blake, let's talk about the, the oldest known Homo sapiens specimen, Omo 1, correct?

Mr. EDGAR: That's correct.

FLATOW: How far back have we pushed Huwea(ph)?

Mr. EDGAR: Well we've almost doubled the antiquity of modern humans in Africa. And this specimen, Omo 1, we had in the first edition of the book. But since that was published people have gone back to the field, John Fleagle and John Shay(ph), among others, to the site in the Omo Basin of southern Ethiopia.

And very interesting they were able to relocate the original site from the 1960s. And that was an expedition that Richard Leakey and Clark Howell co-led that found the partial skeleton initially. They found some additional bones that matched the specimen that had been found, you know, 30, 40 years earlier.

But most importantly they were able to re-date. They found some ash that allowed them to re-date the sediments and found that this specimen was 195,000 years old. The date had previously been very uncertain due to the techniques that had been applied.

So it's amazing. And we also have it in the book side by side with another specimen from Ethiopia that Tim White and his colleagues had found at a site known as Hairtoe(ph) and that one is more than 150,000 years old.

So animals that and people that looked very much like us were walking around even earlier than we thought in Africa.

FLATOW: Talking with Donald Johanson and Blake Edgar, authors of "From Lucy to Language." Does that older age change then the story of how Homo sapiens evolved?

Dr. JOHANSON: Well if I can jump in here, I think that we're now touching on an incredibly interesting part of the human career and that is the question that most people keep in their mind, you know, where did we come from? Where did I come from? Where did Homo sapiens come from?

When I was a graduate student at the University of Chicago, the finishing school for humanity was Europe. That's where we really became who we were. We painted the caves of Lesko(ph). We were the Cro-Magnons and so on.

And of course that was because Europeans were all writing those books, of course. And as we delve deeper into the past, particularly in Africa, we're finding that unquestionably the origins of our own species, Homo sapiens, supposedly wise man as Lineus called us, is quintessentially African.

We don't know if it's Ethiopia or Kenya or South Africa. But we do know beyond the shadow of a doubt now that our immediate ancestors, the people who came into Europe and replaced the Neanderthals, were not white skinned. They were probably very dark skinned. They brought with them very sophisticated technology that we're beginning to see the earliest traces of in Africa.

They brought with them I think fully articulate symbolic language which was probably a product of their life ways particularly as hunter-gatherers. And when we look for the origins of all humanity today, let's not just look at Europe because I think Africa was the cradle, the crucible that created us as Homo sapiens.

FLATOW: I'm Ira Flatow. This is TALK OF THE NATION: SCIENCE FRIDAY from NPR News talking with Donald Johanson and Blake Edgar, authors of "From Lucy to Language." Our number 1-800-989-8255.

This recent discovery of the genetic material from Neanderthal and the possibility of looking at the genome, does that help you guys in any way?

Dr. JOHANSON: Oh absolutely. I was talking this morning to Anne Stone who is here at ASU at Arizona State University. She worked on the original DNA that was extracted from the very first Neanderthal that was found in 1856. And I asked her this morning what she thought of the new work.

We have some new work coming out of the Max Planck Institute in Leipzig, Germany where Svante Paabo is in the process of extracting not just this mitochondrial DNA that's in the little powerhouses of the cell but actual nuclear DNA from the nucleus of the cell.

And he is predicting over the next four or five years to actually produce a Neanderthal genome. It's certainly - the work is in its infancy. But already we know from the sequences that he's looking at that they are not us or we are not them, that Neanderthals were undoubtedly a different species. We can see it now not only in the anatomy and the behavior, the artifacts, the geographic distribution, but we can see it in the genes.

And this takes us back to 100,000 years ago, which clearly shows that Neanderthal genes are not running around in modern humans.

FLATOW: Do you hold out the hope then that we could find genetic material viable, genes that are even older?

Dr. JOHANSON: Well I think so. I think that it again depends on the process of fossilization. We have a project underway at the moment in southern Africa. One of my colleagues at the institute, Curtis Marion, is looking at the evidence for human modern behavior. He has found ochre pencils. He's found engravings and so on that are as much as 70 or 100 or 150,000 years old.

If he can find human fossil remains there in the caves that have been closed like the Neanderthal cave was we might perhaps be able to get very, very early DNA from Homo sapiens.

Dr. EDGAR: But I should point out that it's very hard-won data. Svante Paabo would be the first to tell you really difficulties he has, along with others, have set up strict protocols to try to avoid contamination and make sure that what you're finding is really DNA from the specimen involved.

FLATOW: Mm-hmm. I want to go to the phones and talk to Ed in Ann Arbor. Hi, Ed.

ED (Caller): Hi there. I just had a question. I've heard that some anthropologists and archaeologists have been somewhat reluctant to share their fossil findings, specific measurements of their fossils and cast to the scientific community as a whole.

I was wondering what your panel thought about if that's holding up the scientific process at all. Is that stopping, you know, people from nailing down some of these origins? And I appreciate it. Take my answer off the air.

FLATOW: Thank you.

Dr. JOHANSON: Yeah, I faced this dilemma just after the discovery of Lucy because the Ethiopian government did not have at that time a laboratory to work in Addis Ababa.

And Lucy and the other fossils from Hadar made the trip to Cleveland where I was a curator at the Natural History Museum. And there they were in my lab in the United States. And everybody came knocking on my door with their calipers. Oh, I want to measure this. I want to measure that. I want to photograph this.

And I realized I had a responsibility to share these discoveries with the greater scientific community. And it paid off big because those people found things in the skeletons and fragments that I had missed.

Some of my ideas were wrong and so on. And it opened up a whole generation of scientists right now. And it was very positive. At the moment there are a number of people in the field who have made discoveries 14 years ago and we still have seen them.

FLATOW: We'll talk about it more, come back and talk more with Donald Johanson and co-author Blake Edgar. Stay with us. We'll be right back after this short break.

I'm Ira Flatow. And you're listening to TALK OF THE NATION: SCIENCE FRIDAY from NPR News.

FLATOW: You're listening to TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow.

We've just got a few more minutes to talk with Donald Johanson and Blake Edgar, authors of "From Lucy to Language."

Donald, it seems like the book now is already sort of out of date. You've got to go back a little further than Lucy. And we need a new book soon I would imagine.

Dr. JOHANSON: Well that makes the publishers happy, I think, that we'll have another - I hope will have another edition. But there will be a lot of...

Mr. EDGAR: We could have called it From To Midal(ph) Language but that's less alliterative.

(Soundbite of laughter)

FLATOW: And so just summing up, this is still an exciting time, Don, for paleontologists.

Dr. JOHANSON: Yeah, I think it's a very exciting time because in spite of all of the acrimony and in spite of all of the in-fighting that goes on among paleoanthropologists, there is a general consensus now that all of the important developments in human evolution, upright walking, a separation from the apes, upright walking, acquisition of large brains, production of stone tools, acquisition of bodies of modern proportions, the appearance of Homo sapiens, are all African events.

And that's something that everybody seems to agree on. And what a vindication for Charles Darwin and Thomas Henry Huxley and others who pointed their finger at Africa as the cradle of humankind long before anybody had ever found a fragment of fossil in Africa.

So I think that that is an important perspective that is uniting the field. And all of us are trying to do our best to find the fragments that will help us fill in the details.

FLATOW: Well we will try not to make it another 10 years before we have you back, Don.

Dr. JOHANSON: Well I'm happy to come back any time.

FLATOW: Thank you. Don Johanson, co-author of the revised, "From Lucy to Language," out this year from Simon & Schuster, founder and director of the Institute of Human Origins and the Virginia M. Ullman Chair in Human Origins at Arizona State University in Tempe. And Blake Edgar, co-author of, "From Lucy to Language," an acquisitions editor in the Science Publishing Group at U.C. Press at Berkeley.

Thank you, gentlemen, for taking time to be with us.

Dr. JOHANSON: Thank you.

Mr. EDGAR: Thank you.

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