It's been 35 years since anthropologist Don Johanson found the fossilized skeleton of Lucy, the world's best-known ancestor of modern humans, but Johanson says his 3.2 million-year-old "girlfriend" from Ethiopia still has lessons to teach.
"I never thought, when I found her on that November day, that she would turn out to be such an icon in human evolution," Johanson said last week during a visit to the "Lucy's Legacy" exhibit at Seattle's Pacific Science Center.
Lucy has become an icon, of course. In part, that's because Johanson and his colleagues recovered an incredible 40 percent of the complete skeleton, which is laid out in Seattle like a gem collection in a jewel case. The biggest reason, however, is that Lucy came from an era when our ancestors were just becoming human (as Johanson explains on this marvelous Web site).
"Lucy has gone a long way in introducing people not just to the idea of evolutionary change, but particularly to the fact that humans have evolved," he said.
Courtesy of Donald Johanson
|Anthropologist Donald Johanson holds a
cast of the skull of Lucy, one of the world's
best-known hominid fossils.
Today, the 65-year-old Johanson still returns regularly to Ethiopia, balancing field work with his duties as director of Arizona State University's Institute of Human Origins. His latest book, coincidentally called "Lucy's Legacy" as well, is due to come out next month. And as if that's not enough to keep him occupied, he's giving a series of talks this month - not only to reflect on Lucy's legacy, but also to celebrate Charles Darwin's 200th birthday.
I caught up with Johanson just as he arrived at Lucy's jewel case. "I came to see my oldest girlfriend," he told a museum staffer. "She doesn't get out much."
The conversation soon turned to the Darwin anniversary, and the British naturalist's prescient observation that Africa would turn out to be the cradle of humanity. Johanson took a look around the exhibit space and said, "Would this blow his mind to come in and see something like this?" That provided the perfect opening for our Q&A. Here's an edited transcript:
Cosmic Log: What do you think? Would it blow Darwin's mind?
Johanson: Well, first of all, there are a couple of things that would trickle through his mind immediately. One of them is the fact that Lucy is sort of an amalgam: long arms, small brain, but yet bipedal. ... One of the things that Darwin stressed in his model of human evolution was the acquisition of upright walking. We still think that may be the first distinguishing feature that separated us from a common ancestor with the chimps. He would be gratified to see that.
But he would be mostly gratified when he read that Lucy was 3.2 million years old - because that was one of the things that Darwin struggled with, almost more than anything. We all face it today: We need more time, we need more time. For example, you're taking an exam as an undergraduate, and it's time to turn in the exam. But Darwin really meant it: He needed time, and that really bugged him. The world had to be old for all this to have happened for him. So, how gratified would he be that his predictions turned out to be correct?
Q: I understand that Lucy went through a CT scan, and there's now a virtual Lucy.
A: There is.
Q: Do you feel as if Lucy has taught us everything that she could teach, or are there more things that she has yet to reveal?
A: I think there's a lot more that she has to reveal. It's going to be interesting to see if detailed scans of her teeth come up with something about maturation rate – the rate at which enamel is laid down – and give us an idea of whether she died at 11, 12, 13 or 14. And we just don't know what new techniques will come along that will allow us to look at internal structure. That will tell us more about what kinds of forces were exerted on these bones.
Crown Publishing Group
|"Lucy's Legacy," by Donald
Johanson and Kate Wong, traces
the quest for human origins.
Lucy will always be a seriously important comparative specimen for scholars from around the world to compare their discoveries to. ... One of the things that isn't mentioned a lot is that we now have close to 400 specimens of Lucy's species. We've got everything. We've got a hyoid bone now, from "Lucy's child," the Dakika baby. We've got complete sets of hand bones, we've got complete sets of finger bones, we've got upper limbs, lower limbs, we've got a pelvis, we've got a male skull, a female skull.
At Hadar itself, where Lucy was discovered, we have about 500,000 years of time, and we have about 300 specimens in that sequence. So we're beginning to look at some of the things that Darwin would have been interested in, in terms of tempo. There's a rate and a type of evolutionary change over time, and we're just beginning to examine that. ...
I feel that Lucy's species, Australopithecus afarensis, is the reference collection for everyone who makes a discovery of what they think is a new species of human ancestor. ... That's something that has not been stressed enough. Everyone thinks, oh my gosh, there's Lucy. But if you think of the Taung baby that launched all this in 1925, that's just one specimen. It's a wonderful specimen, of course, and it vindicated Darwin because that was the first hominid fossil found in Africa. But the Hadar collection is unique because it does sample every region of the body.
Q: Do you feel as if the framework for understanding human evolution is pretty well set? Are there certain mysteries that you're looking to solve, or do you think we know what that "bush" of human evolution looks like?
A: I think we have the broad outlines of human evolution. We know that things changed from more apelike to less apelike and more humanlike. But what we'd like to know in detail is, for example, what was the effect of climate change at specific times? What was so unique about this incredible combination of biological evolution combined with cultural evolution that unleashed this incredibly creative species, Homo sapiens? We want to know where that happened, under what conditions that happened.
We think that every major innovation along the way happened in Africa. Why was it Africa? We don't have a very complete answer to that, and we'd like to know why Africa was the crucible. Why was it the place where we first stood up? Why was it the place where we first separated from the apes? Why was it the first place where tools were made? Why was it the place where brains expanded? Why was it the first place where depending on a meat diet happened? Why was it the place where we emerged as Homo sapiens?
That's the mystery. I think that origins in general – origins of the universe, origins of the solar system, origins of humans – all have this mystery associated with them.
Whenever a reporter like you comes along and asks, "Well, what do you expect to find this year?" I always say, "The unexpected." When I was a graduate student, did I think that tools went back 2.6 million years? No. Did anybody even fantasize about the hobbits? Homo florensiensis, which is not Homo ... why would you put it in Homo? I predict we'll see it put into a new genus.
Q: Do you really think Flores Man would go into a genus by itself?
A: It could go in a genus by itself, but you know, it might even go into Australopithecus.
I think that while we have the broad outlines, the areas that bug us the most have to do with the common ancestor. What was it, 6 million to 10 million years ago, that prompted our ancestors to leave the trees? And isn't it interesting that Darwin seems to have gotten that right?
Q: Why do you think he got that right?
A: He looked at a number of things. He looked at chimp and gorilla skeletons, and chimps in zoos in England, along with Thomas Henry Huxley. And he said, boy, their skeletons look like ours. They have the same number of teeth. Chimps, in fact, look a lot like us. And if you go back in time ... clearly you get more apelike, more chimpanzeelike. Darwin said, if those are our closest relatives, if they all look alike, then that's the place where they all evolved. So he predicted, on the basis of those similarities, that Africa would be the place.
Huxley had written about that in 1863. Then, in 1871, Darwin really nailed it when he wrote "The Descent of Man." He said, what's so distinctive about us? Big brains. Chimps don't have big brains. That's a real distinction. But the other thing he saw that humans had was upright walking. And he felt what was so important about that was that it freed our hands. We didn't have to use our hands for locomotion, so we could use them to make and use tools. He got that part right. He thought it all happened together. He got that wrong.
Q: So the follow-up question is, why Africa?
A: I think it's going to be a combination of ecological opportunity, climatic change and the great richness and diversity of Africa. The highest concentration of Miocene apes – species that were more than 10 million years old – was in Africa. It was out of that pool that natural selection could work. But what prompted those first ancestors to leave the trees and begin to walk on the ground? I don't know.
Q: Do you think that human evolution is continuing today? Where are we going?
A: It's more difficult to tell where we're going, because no one can predict the future. Certainly every time a sperm and an egg combine, there's evolutionary change. It's a very microevolutionary change, a gradual small step. But as long as humans around the world are continuing to interbreed with one another, we will probably pretty much stay as we are.
The only exception would be if perhaps someday we are successful in space exploration, and send a mission far out into space. You go out for 200,000 years, and when you come back, you've been gone for 400,000 years. There's genetic recombination, drift, mutation. You might not be able to interbreed with the very people who sent you into space.