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IRA FLATOW, host:

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

Paleontologists are scratching their heads this week trying to figure out what to make of two new fossil finds being announced that threaten to upset the branches on the human family tree.

The new fossils were discovered by scientists from the Koobi Fora Research Project. They work in Kenya under the direction of the famed fossil hunters, Meave and Louise Leakey.

And joining me now to talk about the fossils and what they tell us or what they're going to change possibly about human evolution is one of the scientists on that Kenyan team. Fred Spoor is professor of evolutionary anatomy at University College in London in the U.K. He joins us today from Kenya near the region called Koobi Fora.

Thanks for talking with us, Doctor Spoor.

Dr. FRED SPOOR (Professor of Evolutionary Anatomy, University College London): Good afternoon, for me it's good evening, because we're quite a bit ahead of you, I think, in time.

FLATOW: Thank you for taking time to be with us. Tell us what's - what is so revolutionary about this fossil find?

Dr. SPOOR: Well, as you said, we found two different fossils and both have a slightly separate story to tell. One fossil is a beautifully preserved little braincase of - that we identified as Homo erectus, and what's special about is that it's a really small specimen. It's in fact the smallest adult individual Homo erectus that has ever been discovered. And it points out to us - it showed us that the size variation among the skulls of Homo erectus was really quite large, more comparable to what we see among gorillas today than among modern humans. And that is in itself interesting. This amount of variation usually points at the fact that there might be major differences between male and female individuals of a species.

That and again is interesting to us because it says something usually, at least, among primates large differences between males and females, say, something about behavior. Different strategies of how the group operates. Usually with these large differences it coincides with having a dominant male with multiple females associated with the one dominant male. Your listeners may know about the famous silverback male among gorillas where we have this situation. But among baboons and mandrills, we see the same thing.

FLATOW: Let's talk about a bit more about - the comparison of the two fossils and how they have upset the succession. We thought one was…

Dr. SPOOR: Right. Right.

FLATOW: …descendant of the other.

Dr. SPOOR: So, that's the other story. The other fossil - the second fossil is not as nice, but it's still incredibly informative. A fossil doesn't have to be nice to be very exciting scientifically. The second fossil is a little upper jaw of something that we identified a Homo habilis. And the exciting thing about it is when we asked our geologist how old is this thing, pointing out where we found it, et cetera, they came up with the date of about - just over 1.4 million and that is a good deal younger than we knew that Homo habilis survived. And now, we actually notice Homo habilis survived approximately for the same time that we see Homo erectus here in - on the east side of Lake Turkana here in East Africa.

If fact, Homo habilis and Homo erectus both come in at about the same time, at about 1.9 million. And at about 1.4, Homo habilis disappears, Homo erectus continues then. But it means that they lived side-by-side for about, almost, half a million years and that must surely mean that they really had separate ecological niches to survive in this way for such long time. And then you can ask the question, is it likely that one was actually the ancestor of the other, because classically, Homo habilis has been portrayed as the ancestor of Homo erectus who either gradually or through a rapid speciation gave rise to erectus.

FLATOW: So if he is not - and one was not the ancestor of the other, that you're saying that they lived at the same time, and that means they must have possibly had a common ancestor somewhere there.

Dr. SPOOR: Exactly, exactly. And then the time that this common ancestor lived is - we suspect is between two and three millions years ago. And unfortunately, that is a time period that we have very few Earth layers here in East Africa that produce fossils, and in fact, we only have a handful of teeth and some fragmentary parts of bone from that time period. And so, although we have some candidates that could represent this common ancestor, which could, by the way, be a primitive version of Homo habilis. That cannot be excluded. But we just simply don't know. More research is necessary to find the correct earth layer that link that represents that enigmatic period.

FLATOW: Yes. So what happens many times in science with discoveries is that it doesn't clear up things, it make things murkier.

Dr. SPOOR: To some extent that's true. And brings also things closer to reality. It's always good to remember that if you find five fossils or three fossils, it's very easy to order them usually based on cranial capacity and connect the dots, and, presto, you have a nice linear relationship that represents human evolution from something apelike to humanlike. But as we start finding more fossils, the picture becomes murkier, but life is murky and the reality of the evolutionary process is complex and that's what we increasingly see with human evolution, too.

FLATOW: So would you like - I'm sure it's a self-answering question, but would you like to find fossils from that murky period now?

Dr. SPOOR: Absolutely. And we're certainly targeting in the coming years, particular areas where we know that Earth layers have the right age. Unfortunately, in the past, it has been shown that in those areas, at least where we work here, that it's not very rich in fossils and it will be hard to work to find something. But who knows, we have a great team that's very skilled in finding these things. So, with a lot of efforts - and I should mention with support from National Geographic who has been funding us since 1968 or so, who knows what we will come up with.

FLATOW: Can one fossil find, though, actually cause a change in the whole family tree? Or do anthropologists need to get together and decide amongst themselves to change it.

Dr. SPOOR: No. It's - that question has been asked often - do the schoolbooks have to rewritten, and my answer is no. We - in fact, we know so much already about human evolution that it becomes increasingly unlikely that only one single fossil would overturn everything. To some extent it's our own fault because there's an aspect of marketing where you want to stress how important your find is, but the reality is that even if your find is very exciting it tweaks the picture and it points out that certain things are slightly different.

Sometimes - like in this case where we emphasize that it's not so much a linear pattern of evolution and a more bushy pattern emerges for human evolution, where you have side branches, branches that eventually die out that may be very successful for a long time. That is not necessary completely overturning what we thought before, but it's just adding to the broader picture. So, it's certainly not the case that everything is kind of uncertain and one fossil will do, you know, come up with a completely different scenario. That is not the case.

FLATOW: So where do you go from here?

Dr. SPOOR: Well, as we said indeed, one of the target things that we tried to do here - that is also the strength of this area because it has that period between two and 1.4 million years represented in the Earth layers, we want to investigate what those early phases are of the genus Homo where we absolutely come from, what was going on, and whether there are multiple species, how did they interact, what kind of environments - in what kind of environment did they live, what was their behavior, and of course, and indeed, we would like to know what came before. So over time, we will actually look into that in more detail and try to clear up exactly where our own genus comes from.

FLATOW: Just to put this into perspective a bit. A lot of people are familiar with the Lucy skeleton. Where does she fit into this picture of your findings and in total?

Dr. SPOOR: She lived much earlier on, I should say, around the time periods between her species, Australopithecus afarensis. It is between, let's say, three and three and a half, a little bit older probably three and 3.6 million. So the fossils that we've found, we're talking an age of around 1.4, 1.5. So that is less than half the age. So interestingly enough, the aspects of human evolution between - from 3 million and older to - into 4 million and even a little bit older, we know quite well from some fantastic collections from Ethiopia, and partly from Tanzania, and also a little bit from Kenya.

So we - that older period that we know quite well. And then from 2 million onwards, we know extremely well, as well here from the east side of Lake Turkana and from some other sites. And it is indeed that gap in between that exactly, unfortunately, when all kinds of interesting things happened because, for instance, that is also a period that the first stone tools turned up at about what, 2.6 million both in Kenya and in Ethiopia.

And so we really want - we'd want to know more about that time periods. But fossils - where you find them is dependent on a lot of accidental events. Bones have to fossilize and bones have to come to the surface again by erosion. And you simply cannot choose, you just have to go and look for the right areas and hope for the best.

FLATOW: Do you have to actually dig them, or do you see them lying on the ground or something that sticks out of the ground?

Dr. SPOOR: Well, that's how it starts, indeed. We have a hominid gang, even a, kind of, a young version of the original hominid gang that's worked with Richard Leakey and Kamoya Kimeu. We have a young version of that, although Kamoya is with us here as a great inspiration. And they go around and they look for things and they found, you know, anything up to tiny little mouse teeth -from elephants to mouse, literally. They are fantastic. They observe it. And if we do suspect that there's more and you see things coming out of the rock, you do an excavation. But in first instance, it's a matter of surveying the countryside and follow the layers that have the fossils eroding out.

FLATOW: Well, thank you very much - I know you're busy - for taking time to talk with us, Dr. Spoor. And good luck to you.

Dr. SPOOR: Okay. My pleasure.

FLATOW: Good luck.

Dr. SPOOR: Okay. Thank you.

FLATOW: Fred Spoor is professor of evolutionary anatomy at University College London in the U.K., and he was joining us by satellite phone from Kenya near the region called Koobi Fora where they had made - actually, they discovered these fossils five years ago and it's taken this long to uncover them, clean them off, and actually observe the differences in them.

We're going to take a short break. When we come back, we're going to talk about the energy bill. In the energy bill there's some money for wave research. And companies are already, I guess you could say, farming the seas, getting energy out of the oceans. We'll talk about it. Stay with us after this short break.

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

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