RAY SUAREZ: Last week, the human family tree got a little more tangled. Scientists, seeking clues to mankind's origins, announced they had found a skull that could be an ancestor of modern man. The skull was found in 1999 on the western side of Lake Turkana in Northern Lenya. Approximately 3.5 million years old, it dates from the same period as the famous Lucy skeleton found in Ethiopia in 1974. Until now, most scientists have thought that human descended from Lucy's line. But the new skull, with its flat face and smaller teeth, is considerably different from Lucy, leading its discoverers to declare it a new genus of early human. The head of the discovery team is Meave Leakey, a member of the famous fossil-hunting family who has worked in Africa for decades. She is the head of the paleontology division at the National Museums of Kenya.
RAY SUAREZ: How did you know you had something new, exciting and different when it started to emerge from the sands of Kenya?
DR. MEAVE LEAKEY: We initially just found fragments lying on the surface. And at that point, we didn't know it was new, but we knew it was something exciting. We also didn't know if there would be any more under the ground. So we followed up with a little excavation and found that the entire skull was there. Then when we went to stick the pieces together, that's when we knew that we had something that definitely wasn't like Lucy, so that was extremely exciting.
RAY SUAREZ: Is it a pretty audacious thing to make this an entirely different separate genus and species really separated out from the fossil record so far?
DR. MEAVE LEAKEY: Well, I think "audacious" is perhaps the wrong word. I think it's quite bold. But we wanted to show that this is unlike any other genus known at the time. And to emphasize the differences are really something that are quite significant. And it seems most of our colleagues are relatively happy with the step that we took.
RAY SUAREZ: How do we gradually fit something like this new find, which I guess in Latin is Kenyan man with a flat face, more or less, into the record so far? Do you have to find more individuals in order to really understand better this one?
DR. MEAVE LEAKEY: We always need to find more individuals, and definitely the more you have, the more you understand. We can tell that it's different from Lucy, but we certainly can't say this is definitely the ancestor of us, or that Lucy is definitely the ancestor of us. I think now what this does is emphasize that there are at least two things that could have led to modern humans, and perhaps there are many more that we haven't yet found. I personally think that the more work that we do in that aged deposits that we'll begin to come up with more different genera and more diversity, and then hopefully one day we'll have the answer. Right now we still don't have the answer.
RAY SUAREZ: I guess in the field one of the most exciting aspects of this was that Lucy and this new find are contemporaries. First, how do we know that they were roughly in the same period?
DR. MEAVE LEAKEY: Well, we have very good dates for our deposits. We don't date the bones. We date the deposits, so anything that comes out of certain layers, we know how old it is. And that's really the reason why we were working in that site, because we wanted to know that if we could find evidence of early humans at that age in Kenya as opposed to Ethiopia or anywhere else, that perhaps we would find something different, and as it turns out we did. I'm not surprised that we found something different, because other animals diversify in the same way, and it didn't seem to make sense that humans came from just one lineage. You would have expected that we have a more diverse bushy sort of past.
RAY SUAREZ: But there is only one surviving species of human today. It's interesting to think about a world where there were several at once.
DR. MEAVE LEAKEY: It certainly is, but it's really strange that there's only one left, in fact.
RAY SUAREZ: So how do we extrapolate more about this animal from a skull? Are there things that we can know about how tall it was, how heavy it was, how it used its eyes, or do you... Are you ready for that yet?
DR. MEAVE LEAKEY: There are some things that you can tell. Because the skull is small, definitely it was small. I should think it was about chimpanzee size. To tell things about soft tissue is always difficult with a fossil. But to tell exactly how it moves around is difficult if you don't have the skeleton, because we only have the skull, we can't. But we can tell a little bit about its lifestyle and its diet and those sort of things from the skull. So it had small teeth and so we suspect it probably ate rather softer foods than Lucy's relatives, who have larger teeth. So we can look at things like this and predict certain amount about how it lived.
RAY SUAREZ: Well, what would help you out to find more of right now to understand this animal better?
DR. MEAVE LEAKEY: Oh, if we had some of its skeleton-- its leg bones would be particularly helpful because then we could see how it walked. Its hand would be helpful because then we could see how dexterous its hand was and what it was able to do and these sort of things. Sometimes when I'm asked what I'd most like to find, I say any one of the extremities, either the hands, the feet or the head.
RAY SUAREZ: Why is it that skull bones are more often found and you don't find things like long leg bones or fingers and things like that?
DR. MEAVE LEAKEY: I think most of the things we've found have been chewed by carnivores, because carnivores... our ancestors were food for carnivores. So the carnivores tend to chew up the long bones more than they chew up the skulls, and teeth are very hard so teeth tend to be preserved more than other things.
RAY SUAREZ: Why were you looking there? Did you know what you were looking for?
DR. MEAVE LEAKEY: We always know what we're looking for. We're always looking for evidence of early human ancestors, but we're looking for evidence of other animals as well. In this particular site, it was very fossiliferous; there were a lot of fossils lying around on the ground. So we knew that it was a place that was worth looking, not just for human ancestors but for other evidence, but particularly for human ancestors. We just went there hoping that we'd find something. We were lucky.
RAY SUAREZ: Are we still a long way from knowing whether your new find is a branch of the human tree that just peters out, human tree that just peters out, are we close?
DR. MEAVE LEAKEY: I think we're quite far off, really. One can speculate at this stage. And you can look at the features in the two genera and say, you know, this is more likely to go to us than that one. Some people have looked at the new genus and said perhaps it more likely than Lucy. But I really wouldn't like to say at this point. We're going to now do a great detailed study of the skull, and perhaps that will give us some idea.
RAY SUAREZ: And at the same time, keep looking in that same region of Kenya?
DR. MEAVE LEAKEY: Well, we're looking in the same area but in slightly different sites, trying to look at sediments the same age to see what we can find, yes.
RAY SUAREZ: And I'm wondering how ... When you have the reward of a find that's thought to be so significant, do you go back to the work with a different kind of will?
DR. MEAVE LEAKEY: Well, I think, yes, it definitely is a good boost for morale and helps to be more positive, because it takes a long time to find something like this. And I mean, since I took over the leadership of the field expeditions after Richard, my husband, left to work at the Wildlife Service, I've been looking since 1989 for a skull. So I'm not expecting to find one too soon again.
RAY SUAREZ: Well, Meave Leakey, thank you very much for joining us today.
DR. MEAVE LEAKEY: Thank you very much.