WALKING BACK IN TIME AUGUST 14, 1997 TRANSCRIPT

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The National Geographic Society has announced a "miracle of preservation": fossil footprints made by a modern human 117,000 years ago. Paleo-anthropologist Lee Berger demonstrates the science behind the find and explains what it says about human history.

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A RealAudio version of this interview is available. May 30, 1997: The bones of a boy who lived 800,000-year-old ago may provide clues to the origin of humans. January 23, 1997: Scientists discover 2.5 million-year-old stone tools dating back may date back to the origin of humans. December 13, 1996: Scientists find that Neanderthals may have lived as recently as 30,000 years ago. The complete NewsHour coverage of science issues. OUTSIDE LINKS: The National Geographic Society announces the discovery of 117,000-year-old footprints. Real Audio is available.

PAUL SOLMAN: These are really old footprints--for an anatomically modern human being, the oldest ever found. Here to explain them and how they relate to the origin of our species is Lee Berger, the paleoanthropologist from the University of Witwatersrand in Johannesburg, South Africa, who discovered them--or announced the discovery--sorry--at the National Geographic Society today. It was somebody else who actually discovered them.

LEE BERGER, Paleoanthropologist: That's right.

PAUL SOLMAN: Okay. Well, anyway, welcome. The first question, I guess, is: What have you found?

LEE BERGER: Well, it's really spectacular. Thanks for having me here tonight. What we found is most remarkable find in paleoanthropology.

PAUL SOLMAN: These are not footprints.

LEE BERGER: No. This isn't a footprint I've got in front of me. This find is tremendous because it's from a period of time where we know little or nothing in Africa. It's from a period between about 100,000 and 300,000 years. It is the rarest of the rare. The early hominid fossils you're used to, the Australopithecuses, the ape-men, are common compared to the number of fossils we have from Africa during this time period in the last million years or so.

More anatomically modern than Lucy.

PAUL SOLMAN: Sort of like Lucy that I've seen exhibited. That's from further back.

LEE BERGER: That's right. Lucy dates to about 3 million years ago or so, and to give you an example, there are probably three or four thousand of those early Hominid fossils dating beyond 2 million years in the fossil record. Between about a million years and about a hundred thousand years there's probably less than three dozen from all of Africa. It's that rare, yet, it's one of the most critical periods. These are the kind of fellows that we're finding there. This is, in fact, an anatomically modern human from Border Cave in South Africa. It dates to about 110,000 years old. And you can see that beautiful, anatomically modern outline. But that's not actually what we're here for.

PAUL SOLMAN: Well, let me just understand. But that's which part of the skull, the brown part, the white part?

LEE BERGER: Yes. The brown part is the skull, itself. The white part is a reconstruction. But you can see that beautiful profile of a rounded cranium that's an anatomically modern.

PAUL SOLMAN: Okay. So what about the footprints?

LEE BERGER: The footprints are over here. Can I get up and show you?

PAUL SOLMAN: Yes.

LEE BERGER: This is a fantastic set of footprints. And I know when you first look at this, it, in fact, looks just like a bunch of holes in a cast. But, in fact, this is the best preserved set of footprints from this period. It is, in fact, the only set of footprints from this period, 117,000 years old. These are anatomically modern.

PAUL SOLMAN: These aren't the footprints, themselves. This is a cast of some sort.

LEE BERGER: That's right. This is a cast that we made, sponsored by National Geographic, of a set of footprints in a sand dune about 100 miles north of Capetown on the West Coast of South Africa at a place called Longabon Lagoon. And what you have here is a situation that its preservation is remarkable in and of itself. But here you have where a person walked down a dune onto the beach of that lagoon 117,000 years ago, over 60,000 human generations in the past.

PAUL SOLMAN: But a modern human being anatomically?

LEE BERGER: Anatomically modern human being related to that type of skull that I just showed you a moment also from South Africa. What we have in this situation is--as I oriented--a right-left-right footprint series and then the trail goes back into the dune this way. And if you'll watch as I do what has happened here is this person's walked down the dune. The heel has struck right here, creating this beautiful round impression. The arch goes over, and this is where the foot has actually fallen. You can see that the foot has fallen here and that the toe, the big toe is here, and then these small lunar outlines are where the toes have dragged down through the sand. These big rings are where the sand was pressed away from the interior of the footprint as the foot laid down.

A step by step guide to making footprints.

PAUL SOLMAN: Wait a second. You mean, this is wet sand. You take a step, and it's like you see that little earthquake around where you step in the sand, and that's that circle around it.

LEE BERGER: Just exactly like you would have at the beach today. Now, why is it an angle here? Because this footprint track is on an edge of a dune. It's on that tilting surface, so the right foot is on its edge, just as you might imagine. And as the person takes the next step, they transfer their whole weight to the lefthand foot. And this is where you really get a beautiful look at this fossil. If you'll look here on the ground, you can see this magnificent heel print. Here is the heel print as it soaked down and the full weight of the body was transferred through. The arch went over and right down here on the ground you'll see where the toes went in and this person even 117,000 years ago curled their toes in, in this harsh sand as they put it into the wet, curling their toes away.

PAUL SOLMAN: So this is--now who was this? I mean, what happened here? Can you recreate it at all for us?

LEE BERGER: It's actually a tremendous event, and almost one of the rarest events you could ever see. And I think we've got a picture from National Geographic that was a--

PAUL SOLMAN: A reconstruction, a drawing.

LEE BERGER: --reconstruction they did of this event. If we can have it on screen, what happened was a rainstorm came through here, and it hyper saturated this dune with water. And that storm blew by and then this person came walking along, walked down the edge of that dune, in the wet sand, creating the tracks that you saw. The person then walked on along the lagoon. The wind changed direction, drying the back of the dune, blowing dry sand into the prints, and this miracle of preservation occurred, something that could almost--well, it's only happened four times that we know of.

Was this the genetic Eve?

PAUL SOLMAN: So who was this? I mean, I know you didn't know the person personally, but roughly speculate.

LEE BERGER: This person was a member of this group. This skull was found nearby of an anatomically moderns. As we understand it, according to genetic evidence, humans evolved--modern humans evolved out of Africa between a hundred and three hundred thousand years ago. We call this person the genetic Eve. Every single human being on this plant is descended from a single African who lived in a single population of humans between a hundred and three hundred thousand years ago.

PAUL SOLMAN: You don't mean this person was the genetic Eve. You mean the person from whom we're all descended?

LEE BERGER: This person is not necessarily the genetic Eve, but this person was at the right place, i.e., it was in Africa, and in particular in South Africa, where the very best fossil evidence for the origin of modern humans is. And this person is at the right time. A hundred and seventeen thousand years is within that narrow window. And even more so it's from South Africa, where the best fossil evidence is. It could have been Eve, although that's kind of a whimsical association.

PAUL SOLMAN: The odds have to be fantastic that that's actually the footprints of the genetic Eve, the theoretical--

LEE BERGER: Absolutely. But the odds are quite good that this person carries the genetic potential of living humans.

The implications for racial differences.

PAUL SOLMAN: But if it's 117,000 years ago that we're all descended from the same person, then racial differences as we define them now are that recent?

LEE BERGER: Racial differences are far more recent than that. Racial differences that we see today--as the diversity we see today--are very recent. The last thirty-five, the last forty thousand years, or even younger than that--this person was a black African. We know that because they're from Africa, and that's what color people are. But the fact is that this person was where people radiated from. Racial groups would only develop after people entered Europe, Asia, other areas tens of thousands of years--fifty, sixty, seventy thousand years after these footprints were made.

PAUL SOLMAN: I thought there was a big debate about out of Africa versus multi-regional evolution and--that is groups evolving the--humans evolving in different parts of the world. Is that not still a controversy?

LEE BERGER: No. I think the out of Africa people won. Combined genetic evidence--combined with the evidence that humans all originate from African population I think there's a large consensus among geneticists that's true. And with the fossil record, which clearly indicates so far that humans evolve out of Africa, then the multi-regional idea seems dead in the water.

PAUL SOLMAN: So, briefly, what's the significance of this for you? I mean, this is thrilling, but larger significance.

"We are all Africans."

LEE BERGER: There's a few points. One, that this is only one of four sets of footprint ever known from Africa. It is the rarest of rare finds. It is from a critical time period, and to me, the emotive situation is it represents an ability to touch one of our own ancestors. You can place your hand or foot in this matter in what is living evidence of one of our ancestors, not dead evidence. A fossil is, in fact, in a way unfortunately dead evidence. It's graveyard evidence. That is evidence of a living, breathing human being who walked on a beach 117,000 years ago.

PAUL SOLMAN: And so it's your ancestor and mine? I mean, you think that's a lineage--that's our lineage there?

LEE BERGER: We will learn from this that we are all Africans. And that is a fact.

PAUL SOLMAN: That we're all Africans?

LEE BERGER: We're all Africans.

PAUL SOLMAN: Did this person think like a modern human being? I guess that's the last question I have. Do we know? What do we know about how this person--

Just how modern?

LEE BERGER: What we know is while this person would have looked like a modern human being, this person did not think like a modern human being.

PAUL SOLMAN: You have more things here.

LEE BERGER: I've brought along some little toys in my top to show you the magnificent tools, the magnificent and beautiful tools that this person would have made. And as beautiful and complex as these were 120,000 years ago--and these are 120,000 years old--as complex as they are, they were not very diverse. It would be another fifty to seventy-five thousand years before humans would develop the infinite tool kit, develop burial of the dead, develop complex artwork. This human didn't think like humans.

PAUL SOLMAN: Okay. Well, thanks very much. It was really interesting, I appreciate it.

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