Paleontologists Unearth Possible Pre-Human Fossils

Fossils discovered in East Africa suggest that Homo erectus, the species believed to be humans' direct ancestor, may have shared Earth with two genetically distinct but similar species. Some paleontologists believe that these species may be distant relatives to modern humans, while others need more evidence.

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TOM GJELTEN, HOST:

This is TALK OF THE NATION. I'm Tom Gjelten.

A new fossil has been found in East Africa: A flat-faced skull two million years old of a human ancestor. That discovery suggests that Homo erectus - that's the species believed to be our direct ancestor - may have been on Earth at the same time as two other human-type species, genetically distinct but similar. The discovery sheds new light on the long-standing question considered by evolutionary biologists: How many species in the same biological group as our ancestors inhabited the Earth together? Three? Two? Or did we evolve step by step through one species at a time? How many distant relatives do we have? Or is further information needed?

If you have questions about these findings and what they mean, give us a call: 800-989-8255. Our email address is talk@npr.org. And you can join the conversation on our website. Go to npr.org and click on TALK OF THE NATION. Christopher Joyce is an NPR science correspondent and he joins me now in Studio 3A. Chris, welcome back to TALK OF THE NATION.

CHRISTOPHER JOYCE, BYLINE: Glad to be here, Tom.

GJELTEN: So before we get into all the details of this new fossil finding, let's make sure that we understand the context here. I briefly mentioned that there's, for a long time, been this - been curiosity about how humans evolved, of course. And tell us: What are the big mysteries that we are still trying to figure out?

JOYCE: OK. I'll try, although I must admit that, you know, five minutes from now, it will change. That's the way it works in anthropology.

GJELTEN: Yeah.

JOYCE: For a long time, there was this sort of notion of a linear line of evolution for the human species. Basically, there was this creature that appeared around 2.3 million years ago, small brain, pretty primitive, ape-like, but it had tools with it. So a lot of scientists said, OK that's where we start the human line, tool-making, Homo habilis, the toolmaker or handyman.

GJELTEN: Mm-hmm.

JOYCE: Then around two million years ago, they found another creature arrive in East Africa, Homo erectus. Much more like us, walked erect, obviously, but fully erect and not so ape-like, bigger brain. And this was clearly - we thought, OK, this is where we came from.

GJELTEN: Right.

JOYCE: And then about 250,000 years ago, then we came. Keep in mind also that habilis, the first one, toolmaker, and erectus seemed to overlap some around two million years ago so this...

GJELTEN: So we already knew that there were at least two species at that time.

JOYCE: Yeah, there were two. Around two million - and this two-million-year period is pretty interesting because there seemed to be a lot going on. So that was just this linear idea. So along - about by early 1970s, they found this weird fossil. It was a partial skull, not very much to go on. But it didn't look like erectus. It didn't look like habilis. There's not much of habilis to compare it to, so they didn't know where to put it and it sort of sat there. And some people said, oh, it's a new species. So yeah, you know, we've got this bushiness. We've got yet more species of humans around two million years ago. And other people said, no, it's just a weird Homo erectus. I mean, there's variation in all species. You can see it now. We've got pygmies and big seven-foot basketball players so, you know, it's just an outlier. And so that's been controversial.

So now comes this new discovery - this is Meave Leakey, the famous Leakey family, that really opened up evolutionary studies in East Africa - three fossils, three individuals: a skull and a face, pretty intact, pretty amazing a lower jaw and another partial lower jaw. They do not look like - and they came from two million, well 1.9, and they do not look like erectus. They don't like Homo habilis. They look like this 1470 that was discovered in 1972, this supposed outlier.

And so what she said is, look, it's not just one individual that looks like this. We've got four. So it had to be another species. So in that sense, is it brand-new hypothesis? No, but it's what they say is confirmation that there were then erectus, habilis and now this other one, all contemporaneously living, walking the same walk supposedly around the same place in East Africa.

GJELTEN: So if there were, in fact, three different humanoid-type species living together - I mean, living simultaneously - does that necessarily mean that there were three branches or, you know, what does that sort of suggest?

JOYCE: Hard to say, although I think right now nobody would go beyond saying that, look, it's clear that we came from erectus. It's so similar to us. We have so little to go on on these others. I mean, Leakey's recent discovery is just a few fossils. I mean, you could fit all the fossils from this period into a big suitcase.

GJELTEN: All of the fossils that have been found.

JOYCE: Right. Yeah, one or two big suitcases from this period: habilis, erectus and this other 1470. So, you know, people are going on the most minute amount of information and the difference between, you know, the shape of the crown of a tooth, the shape of a jaw. And so it's pretty tough to tell, you know, what they were doing, whether they were really different, were they competing with each other. All we know is that they were contemporaneous, and obviously, a couple of them - if there were really three - didn't make it.

GJELTEN: Yeah. So what are the alternative scenarios, here? One is that these are sort of branches of the human ancestral family that sort of took off in one direction and then, for one reason or another, came to a halt.

JOYCE: Right. And that, you know, and that isn't - shouldn't be terribly surprising to people. I mean, if you look outside of the human line, that's the nature of almost all species. I mean, you look back at early squirrels or, you know, whatever, other primates. There were lots of experiments, if you will, that didn't make it.

GJELTEN: Experiments that didn't make it, people that just didn't - or species that didn't adapt to the surroundings in a successful way. Travis is on the call - is on the phone. He's got a question from Shasta, California. Good afternoon, Travis.

TRAVIS: Yeah. Thank you for taking my call. I was curious about where you're finding these fossils, say, the layers of Earth. Are these deep down? Are these on the surface caves? Where are these coming from?

GJELTEN: Have you ever been on a dig, Chris?

JOYCE: I have been on a couple of digs of various kinds, more archeological than this kind. I've not been to East Africa, and I'm dying to go, let me tell you. These are buried, but what happens is that they get uncovered by erosion. This is why this is - this area is so hot and so good for finding fossils. And so I believe most of these have been found either on or near the surface. But they know the layers from which they come, and they can date those layers using both the sort of sequence of the layers, knowing how long it takes to lay down a layer, plus something called argon-argon dating, which is a form of updating some of the elements in the volcanic material that gives them a really good, hard date.

GJELTEN: Now, how can scientists, archeologists reconstruct an entire skeleton and even sort of have artists draw a picture of what that individual looked like when they're only working with so few bones? You said all these fossils could fit in a suitcase. How were they able to reconstruct? What distinguished one species from another?

JOYCE: Well, there's a lot creativity involved, you know? You know, I mean, I wouldn't necessarily rely on all the recreations that you've seen. But, you know, the basic form - and you have - so often have a fossil that you have part of the cranium and you might have part of the jaw, and you might have a leg bone and an arm bone. And, you know, we can extrapolate from that pretty much what the size of the organism and the shape of the bone tells you how it walked, that sort of thing.

GJELTEN: Travis, did that answer your question?

TRAVIS: Yes. I'm just curious of, you know, if they're that old, where they're being found and how they're being turned up.

GJELTEN: Right.

TRAVIS: So thank you very much.

GJELTEN: OK. Thank you for the call. Let's go now to Christopher, who's on the line from - well, first, I got to get rid of Travis. OK, Christopher, on the line from Jacksonville, Florida. Hello, Christopher.

CHRISTOPHER: (technical difficulties) for taking my call.

GJELTEN: Yeah.

CHRISTOPHER: I'd like to comment and hear the guest's thoughts about the so-called hobbits that were discovered in recent years in Indonesia, which - I don't think there's a consensus, but I think that there is a fair number of scientists who believe this was a hominid, not an immediate relative of ours, perhaps descendant from something other than Homo erectus. It was living as recently as 18, 20,000 years ago. Does that - I just wonder - it seems to me further evidence, if that's correct, of the idea that there was a bush, like, rather than a direct lineage of various hominids.

GJELTEN: All right. Christopher, thanks. Well, Christopher Joyce, 18 or 20,000 years ago, I mean, humans were well-established by then. So this clearly was not some ancestor. Were there - I mean, how far can we go with this idea that there were other branches that went off for a long, long time perhaps, and produced some interesting creatures? He called this a hobbit. I haven't heard that one before. You probably know about it.

JOYCE: Yeah. That this is also known as Homo floresiensis. It's a really interesting question, Christopher. And I think you pretty much nailed it, although I think the consensus is that Homo erectus left Africa a million or two years ago, and some of them ended up in Indonesia, what is now Indonesia. And there were a pocket of them of living on this island, and they evolved into the hobbit while the rest of the world was taken over by us, or - and by Neanderthals for a while.

But to go back, Tom, to your comment, is that, I mean, you know, this idea of branching, I mean, obviously, Neanderthals were a branch of our own species, quite recent. I mean, we, you know, they didn't die out until the last 40, 50,000 years. And so, you know, there are these experimentations that evolution, you know, I don't want - I don't mean to say evolution has a will, but natural selection comes up with different models of all species, and we're really no different.

GJELTEN: And isn't it true that scientists now think that they may have even been some interbreeding between the Neanderthal and Homo sapiens?

JOYCE: Well, speak for yourself, Tom.

(LAUGHTER)

GJELTEN: Yes. Well, you know Homo sapiens just, you know, incorporate a wide variety.

JOYCE: But there is a point I want to make, very quickly, is that one of the interesting things about this, you know, people may say, OK. So what? So there were three or four versions of us, and they died out. One of the things that this is useful for is trying to determine what made us special. Why did we make it, and why did they fail? And what is it that makes humans humans? And, you know, the more we can look at the different experiments that failed, then we - we take a look at what they look like and take a look at what we look like, what our ancestor erectus looked like, and differentiate and say: What was it about erectus that made it end up surviving to become us, and that the others died out? Was it the, you know, was it the arch of the foot?

GJELTEN: Was it the intelligence?

JOYCE: Could be the intelligence, but intelligence is - doesn't come about all by its own. I mean, some people say, look, the foot gave us our brain because it allowed us to run. We have an arch. Chimps and other apes do not. The arch gave us the ability to run. We could hunt. When we could hunt, we could eat more meat. More calories meant a bigger brain. You know, that sort of hypothesis is widespread. And so when you see these differences between the experiments that failed and us, you get an idea of, gee, you know, this is the course that we took that ended up being successful.

GJELTEN: Well, you've done some really interesting stories in this regard, Christopher, and I can imagine, as a reporter, how fascinating they must be.

Ken is on the line from Memphis, Tennessee. Good afternoon, Ken. Welcome to TALK OF THE NATION.

KEN: Oh, thank you. Chris mentioned in earlier conversation that these three different species were found in the same general area. Is anybody offering the observation that there was an interaction between the various species?

JOYCE: I don't think they are - I don't think they'd be willing to do that because there's just no evidence of saying that. You know, one could assume, but it depends on how different - you know, Homo habilis, Homo erectus and this other one, which they have not named. You know, again, we're talking about tiny bits of bone here. But I think it's an interesting question. You know, what do they think of each other? It's interesting to speculate. Would they even have recognized a difference?

I mean, when a red squirrel looks at a black squirrel, do they know the difference? And yet, you know, these creatures had, you know, brains that were the biggest of the time. And so you have to wonder: Did they compete? Did they breed? It's so far back that, you know, I don't think that people will ever be able to tell that.

GJELTEN: And you say that they live simultaneously, but we're using that term a little loosely, aren't we? I mean, we're talking, give or take, 200,000 years. That's kind of a long time.

JOYCE: Yeah, yeah, yeah. That's true.

GJELTEN: So we - really, there's no way of knowing whether they actually came into contact with each other, you know, exactly at the same time. So this is - do you think, Christopher, that this - I mean, we are so hungry, as consumers of information, for news about, you know, our ancestors that we jump on a new story like this. Do you think that this development this week, this article that was discussed in Nature magazine this week, do you think it's probably getting more attention than it deserves, in a sense?

JOYCE: Well, I agree with you that I think the public at large and people who are interested in science do - are fascinated with this. I mean, this is our story, you know, and that is - what could be more interesting than what makes us what we are? That said, you know, this was something that people thought was true, and so this week's information basically says, well, yeah, we have more evidence. It's not fully accepted. Already, there are plenty of scientists saying, sorry, this isn't enough evidence, maybe like (unintelligible) we don't think that you've got it yet.

GJELTEN: So there's been a bit of (unintelligible) about this?

JOYCE: Oh, yeah. Well, there always is in this field. I mean, you're talking about a field with very few people and very little money. And usually that's, you know, the controversy is in the inverse proportion to the amount of money that you've got. So, you know, these people go at each other a lot and, you know, accuse each other of pushing stuff. I mean, there are people who are conservative and say, let's not call this a new species yet till we have more evidence, or other people leap on it because, face it, I mean, naming a new species is a feather in your cap. It gives you a lot of notoriety.

GJELTEN: No one has come up for a name for this possible new species yet, the one that...

JOYCE: Homo Gjelten, I think, would be a good, I think. What do you think?

GJELTEN: I'm not sure. I'm not sure about that. No. It says it had a flat face. I mean, you know, this is...

(LAUGHTER)

GJELTEN: ...it doesn't look to me like this was a particularly attractive species the way it's been described in the magazine.

JOYCE: Well, certainly not as tall as you are.

(LAUGHTER)

GJELTEN: All right. Daniel is on the phone from St. Louis, Missouri. Daniel, thanks for the call.

DANIEL: Hi. I was actually - well, I am a - I'm a college student, and I'm currently running through my classes trying to become a anthropologist-archeologist, and I was a little curious. How is it that you're able to tell specifically this is a new species instead of it just being another version of an already known species with the compressed face from being stepped on by, like, an elephant or something?

(LAUGHTER)

GJELTEN: Well, you did mention that there are now two skulls that have this stepped-on face.

JOYCE: Well, no. What Meave Leakey found this time is a very nice, fairly complete skull with a face, a lower jaw and a partial lower jaw with some teeth. So, I mean, that gives them a fair number of things. And what - the reason - and that's a good question, because there are scientists who are saying, no, this is not - you don't have enough to say it's a new species. It could be Homo erectus, or it could be Homo habilis or something.

But they're saying it looks really a lot like this mysterious 1470 that was discovered that couldn't be placed, and 1470 and these three all looked to be similar to each other, but different from everything else we have at the time. And so from that, Meave Leakey is saying, we think that this is the species, but not - she's not even sure enough to give it a name.

GJELTEN: Well, I guess we'll see even more hunting in East Africa for new species. NPR's Chris Joyce joined me here in Studio 3A to talk about this new fossil discovery. Chris, thanks for being with us again.

JOYCE: Lots of fun.

GJELTEN: Tomorrow, it's TALK OF THE NATION: SCIENCE FRIDAY with more on Mars rover Curiosity's mission, and your host, Ira Flatow, is going make all that science stuff clear and interesting. This is TALK OF THE NATION, from NPR News. I'm Tom Gjelten, in Washington.

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