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"Would you like to see Lucy?" Johanson asked him, and Kimbel, of course, did very much.
Johanson had the original fossils, set into foam-rubber forms in a couple of boxes. He asked Kimbel to have a seat and then set the open boxes on the desk before him.
"I'm going to a meeting. I'll be back in an hour," he said. Kimbel was a 20-year-old college junior left alone with a priceless scientific treasure.
"I was awestruck," Kimbel says. "It was a defining event of some passion."
Kimbel went on to earn a Ph.D. in anthropology and later to become Johanson's closest associate at IHO.
Johanson had his first encounter with the theory of evolution when he was a boy in Chicago, left to roam the library of his mother's friend, a man he refers to as his surrogate father.
"I remember being intimidated by Darwin's Origin of Species because there weren't any pictures in it," he says. "There was one illustration which was a family tree of evolution, which Darwin also got right. It's a bush. It's constantly branching."
As an adult, Johanson helped fill in the details of the human branches on Darwin's bush.
Two of those branches are two main genera of hominids, Homo, to which modern humans, or Homo sapiens, pertains, and the smaller-brained and more apelike Australopithecus. Tim White is now proposing a third, even more apelike genus, Ardipithecus, but will not reveal details until he has completed study of his fossils.
But the debate between the Leakeys on one side and White and Johanson on the other centered on whether Homo developed out of Australopithecus or whether the two evolved from an earlier ancestor and developed on parallel tracks. In fact, various species of Homo and Australopithecus lived at the same time.
In 1972, Richard Leakey had unearthed a fossil skull of the species his father, Louis Leakey, had already named Homo habilis, or "handy man," because of his apparent toolmaking abilities. At more than two million years old, it furthered the Leakey family theory that man's ancestor was a large-brained Homo.
When Johanson found Lucy two years later, he was not sure what he had. He kept searching and, in 1975, discovered a trove of more than 200 more hominid fossils in Hadar, near where Lucy had turned up. Those fossils belonged to several individuals, as if a family group had died together. Johanson and his colleagues called them "the first family," but because some of the bones were so much larger than others, they were not sure if they composed one species or two. The Leakeys pronounced them two separate species; but a defector from the Leakey camp helped Johanson decide otherwise. Tim White was then a University of Michigan graduate student working with Richard Leakey at Olduvai Gorge in Tanzania. When he examined Johanson's first family, he deduced that they were a single species, but that the males were significantly larger than the females, a trait called sexual dimorphism, which is common among apes.
Johanson re-creates the logic on a recent afternoon in Berkeley, using IHO's extensive collection of fossil casts.
"These are like baseball cards," he quips as he lifts and examines plaster bones in the collection's many drawers. "I'll give you a Lucy jaw for a, you know . . .
"Here's Lucy, the top end of her femur," he says, laying the cast on a table.
He chooses a cast from the first family. "Ah, here's another femur: Look at the size of that!"
It's twice as large.
"Okay, hypothesis number one," he says, lifting the bones in turn. "Species A, species B. Then you start finding a pattern, a whole group of big ones anatomically identical to the small ones."
He lays out several of intermediate sizes.
"Hypothesis two--which you can never prove because we can never go back to see--there is sexual dimorphism like in modern-day apes."
To reinforce the point, he selects a cast of Lucy's jaw, then places next to it a much larger one.
"Was that her husband?" he asks. "They're right there in the same area."
With that logic, back in 1977, White and Johanson opted for hypothesis two, and they chose a name for their species: Australopithecus meaning "southern ape," and afarensis after the region of Afar where they found it. Based on thorough studies of afarensis and Homo jaws and teeth, they decided that the bush of evolution had branched at afarensis, that some dead-end species of Australopithecus had arisen, but also the earliest species of Homo. Lucy, in essence, was man's ancestor, and not just a hominid reject of Nature.
Mary Leakey, Richard Leakey's mother, had found jaw fossils similar to Lucy's in Laetoli, Tanzania, along with two sets of hominid footprints forever preserved in a lava field. White and Johanson offered to include Mary Leakey as an author on their journal article officially announcing afarensis. Both Johanson and Leakey were to speak about the finds at a Nobel symposium in Stockholm that was sponsored by the Royal Swedish Academy of Sciences.
Johanson was in the airport en route to Stockholm when he got the phone call saying that Mary Leakey no longer wanted to be included in the authorship for the paper.