January 23, 1997
Some tools that are 2.5 million years old were found in Ethiopia by a group of scientists from Rutgers University and reported on in the journal Nature. Here to tell us about it is Richard Potts, director of the Human Origins program at the Smithsonian Institution.
JIM LEHRER: How many--first of all, the basics. How many of these objects have been found?
RICHARD POTTS, Smithsonian Institution: There were nearly 2,000 stone artifacts uncovered by excavation, by digging into the ground in Ethiopia at the site called Gona.
JIM LEHRER: Now, how big are each one of these? What's the average size?
RICHARD POTTS: Well, I have brought, in fact, some examples here, not of the artifacts from Gona.
JIM LEHRER: You didn't bring them directly from Ethiopia?
RICHARD POTTS: Not from Ethiopia.
JIM LEHRER: But they are similar?
RICHARD POTTS: They're very, very similar.
JIM LEHRER: All right.
RICHARD POTTS: And they're almost as old. For example, this particular one right here is a stone tool from Northern Kenya, not too far away, which is a little bit over 2 million years before the present. And you can see that it fits nicely in the hand, and this is one kind of tool that was found. Then there were the sharp flakes that came off, that flew off a rock like this when it was struck. And they are of a size like this also. They sit nicely in the flake and are very sharp and used for a variety of purposes.
JIM LEHRER: Now, how do they know these, or the ones that were found, are tools? They look like rocks. They look like rocks.
RICHARD POTTS: Indeed, they are rocks. They began that way.
JIM LEHRER: Right.
RICHARD POTTS: The great finding of rocks that are 2 ½ million years old that were modified by humans is that it's the beginning of a human--of the human technological venture. How we know is that there is a particular pattern. Again, on this one you can see that there's a pattern to the scoring on the rock, which is a kind of pattern that does not occur in nature, unless you have a whole lot of other rocks around it that are all jumbled together, such as in a river. The rocks that were excavated of this age are all made in the ancient past that was a much more gentle environment. There weren't any other rocks around, and so all of the rocks were modified in a patterned way, indicating human activity.
JIM LEHRER: Human activity. What kind of uses were these tools put to?
RICHARD POTTS: That's also a good question. There has been some research done on that in tools that are a bit later but of the same kind of technology. And it turns out that we used to think that it was this kind of rock, this kind of tool that was used, the one that would flake. It now appears that the kind of wear we see on the edges that it was the actual flakes, the slivers of rock that were used, and they were used for a variety of things like butchering animals, perhaps sharpening sticks to dig up plant or foods that were underneath the ground, and a variety of tasks like that.
JIM LEHRER: How do the scientists know that these rocks, the 3,000 rocks, are, in fact, 2.5 million years old?
RICHARD POTTS: Indeed, there is a way of dating the dirt around where the rocks were found. There's a volcanic layer above the rock which can be dated through a technique called argon technique. It's like a clock, a radioactive clock, and the geologists are able to measure the amount of potassium, the amount of argon, and are able to look at the ratio between the two. And we know the rate at which one decays into the other. And it's a clock. It tells us 2 ½ million.
JIM LEHRER: And it's not a debatable subject anymore, right?
RICHARD POTTS: That's not a debatable--
JIM LEHRER: Nobody disagrees that these rocks are 2.5 million years old.
RICHARD POTTS: That's right. It's quite firmly established by today's report.
JIM LEHRER: Okay. Now today's report does jar some previous thoughts about when humankind began, is that right? Explain that. Why is this so significant?
RICHARD POTTS: This is the beginning of technology, and we've long considered this to be a major hallmark of our evolutionary history. And, indeed, it is. It's interesting because these stone tools are slightly older than the oldest fossils that belong to our branch of the family tree, the genus Homo as it's called as in homosapiens. The oldest fossils of our biological genus are about 2.4 million years old, a couple of hundred thousand years, or one hundred thousand years later than the earliest tools. Well, it opens up a big mystery. Who was the tool maker? We have earlier members of our family tree. The genus name is Australopithecus. And they were known for having an ability to not only walk around on two legs--
JIM LEHRER: There we go. We've got pictures of--they look kind of similar from here.
RICHARD POTTS: They look pretty similar, but the one known as Australopithecus had an ability to climb in the trees. The one known as Homo had a slightly larger brain. While we have always been thinking that stone tool-making was a pretty complicated activity--
JIM LEHRER: You had to think about it.
RICHARD POTTS: You had to think about it.
JIM LEHRER: You invented it, kind of.
RICHARD POTTS: That's right. But as you can see right before you with these tools that this kind of technology is actually pretty simple.
JIM LEHRER: Yeah. But is there any--does this mean that there's going to be a whole new search for the answer to that question you just posed, who these people were, what size their brains were, and all that?
RICHARD POTTS: There must be. The time period between two and three million years before the present is a real mystery. I mean, we have quite a few fossils and quite a few stone tools, but it's not--not the density of fossil evidence that we normally would like.
JIM LEHRER: For those of us--explain what fossil evidence is for somebody like you.
RICHARD POTTS: Sure. For example, the bones of our ancestors, when those ancestors died, the bones were--in some cases--were buried. You're very lucky if you get buried, and just by natural processes, and then the minerals from the dirt, the soil, begin to infuse the bones, harden them up, make them basically just like rock but preserving the look of the actual bone, itself. But we also have fossil behavior once you have stone tools. The ability of these early humans to make tools is fossilized in the ground in the form of these tools.
JIM LEHRER: So for somebody in your line of work this was an exciting day.
RICHARD POTTS: Tremendously exciting indeed.
JIM LEHRER: Thank you for sharing it with us.
RICHARD POTTS: Thanks.