Solving the Human Mystery

Nobody knows for sure where we came from, but folks at Berkeley have more clues than most

The most famous fossil in modern history was given her nickname — “Lucy”— after the in-the-sky-with-diamonds Beatles song that played over and over on a tape recorder, during a drink-enhanced all-night celebration at a campsite in the barren wilds of Ethiopia. The year was 1974.

At three and a half feet tall, Lucy was the oldest little lady in the world, a hominid, or two-legged primate apelike human relative, who had lived about 3.2 million years ago. Her remains, or the 40 percent that were found on that historic occasion, told the world details of a new stop along the path to modern humans. She walked upright, yet her brain was small, like an ape’s. She was a new species, Australopithecus afarensis, and perhaps the mother of us all. The press loved her.

TWO DECADES later, in a badland moonscape just 46 miles away from where Lucy had lain, Yohannes Haile-Selassie, an Ethiopian-born Berkeley graduate student spotted a piece of bone from the palm of a hominid hand. That find led to over a hundred more pieces of the disarticulated, scattered skeleton of one individual creature, a female, and eventually parts of at least 36 other individuals from the ancient floodplain.

Determining what they truly were, in the cautious way of science, took 17 years of assembly, analysis, and interpretation. The results were announced in October of 2009, as the cover story in the Everest of journals, Science, in 11 papers by 47 authors from 10 countries. The cover girl was the “type specimen” (or principal reference fossil), the 45-percent-complete female skeleton from the site known as Aramis in Ethiopia’s Middle Awash area. She was 4.4 million years old — more than a million years older than Lucy, and therefore held the new record as the oldest fairly complete hominid specimen ever discovered. She was taller — about four feet — and weighed in the neighborhood of 110 pounds.

She, too, had a nickname — “Ardi” — a very straightforward, unromantic shortening of her full appellation, Ardipithecus ramidus. She, and her fragmentary disinterred companions, represented a new species, possibly ancestral to Lucy. (And, because Lucy was still a possible forebear to modern man, conceivably part of a direct, connect-the-dots line to you and me.)

AT THE END OF 2009, looking back on the year as publications like to do in December, Science named the discovery of Ardi the “Breakthrough of the Year.” And Time magazine ranked the find number one on its list of the year’s Top 10 Scientific Discoveries.

Ardi has not yet become a household word as Lucy did, perhaps in part because of her less mediagenic nickname. But word of her and her kind was quickly reported, and commented on, around the world.

Alan Walker, a paleontologist from Pennsylvania State University and not part of the research, remarked that “This find is far more important than Lucy. It shows that the last common ancestor with chimps didn’t look like a chimp, or a human, or some funny thing in between.” (Indeed, though her brain was one-fifth the size of what’s normally in a Homo sapiens skull, Ardi had a small face and diminutive, diamond-shaped, blunt canine teeth, unlike chimps, and her pelvis, feet, and hands indicate that, like the later Lucy, she was bipedal, an upright stepper, not a knuckle-walker, although still somewhat adapted to tree-climbing.)

Some observers wondered why the findings took so long to become public. Part of the explanation lay in sheer quantity: two of the 11 papers, for instance, analyzed more than 150,000 plant and animal fossils in order to reconstruct the environment near the site (and revealed 20 species new to science, among them bats, shrews, and various carnivores, hares, and rodents).

And there was the nature of the remains themselves. Found because they erode out of sediments they were buried in, the fossils have survived so many years of rain and wind that little is left. Team member Leslea Hlusko, a Berkeley associate professor of integrative biology, says, “I am awed by the fact that the team was able to recover bones that were so fragile; just breathing on them would cause disintegration.” They managed that by hardening both the bones and the surrounding sediment, then excavating a wide margin around the bone so soil and bone stayed intact, and wrapped plaster bandages (as used to set broken arms) around each chunk. Then, in a lab, the sediment was removed, grain by grain, from the fossil bone. “It takes a lot of patience,” says Hlusko, “and is incredibly time-consuming.”

For all its vastness, the Ardi project, and its own evolution, are intimately tied to Berkeley. Of those 47 authors of the debut papers, 19 trace their roots to this campus. Many Berkeley students, both graduate and undergrad, were involved in the research, in the field and in labs.

Project co-director Tim White, an integrative biology professor here, did all of the preparation work for the Ardi skeleton, Hlusko says, and he’s “the best in the world at this.”

White, a Cal faculty member since 1977, is a major player in Berkeley’s huge contributions to knowledge about human evolution. Before joining this faculty, he worked with two members of the most famous family in paleoanthropology, Richard Leakey and his mother Mary Leakey, in Kenya and Tanzania. Once here at Berkeley, he collaborated with Donald Johanson — who discovered the Lucy skeleton — on determining that she and her kind in fact fit into our evolutionary heritage as a new and separate species. (Johanson, who had been a leading anthropologist at Case Western Reserve University, moved to Berkeley in 1981 and remained here for 17 years.)

In addition to his noted skills at preparing and analyzing specimens, White is globally renowned as a hawk-eyed fossil-finder. He’s also gifted at spotting, and nurturing, talented students in his field, and some of his living human “finds” played key roles in the huge project around Ardi and her kin, Yohannes Haile-Selassie among them. Like Tim White, Yohannes Haile-Selassie has the “golden touch” for paleoanthropological fieldwork (“Just like playing a piano or pitching a baseball,” says White, “some people really have that talent and some people don’t.” Haile-Selassie’s got it.).

In 1997, he discovered fragmentary but toothily convincing fossils from an even older relative of Ardi, Ardipithecus kadabba, which has been dated between 5.6 and 5.8 million years ago, making it the earliest hominid species unearthed so far. He is presently curator and head of the physical anthropology department at the Cleveland Museum of Natural History — the position Donald Johanson held in 1974, when he found Lucy.

Another tipping-point person was Gen Suwa Ph.D. ’90, currently of the University of Tokyo. A former grad student of White’s, Suwa was surveying the Aramis site in 1992 when he discovered, among the pebbles, a primitive tooth, the researchers’ tantalizing first glimpse of an Ardipithecus remnant. Two years later, Haile-Selassie found the hand-bone of the Ardi skeleton. In a Tokyo lab, Suwa scanned numerous bones from Ardi that had been damaged over the millennia, using X-ray microtomography, and digitally reassembled the fragments. White, meanwhile, used plaster casts and physically performed a similar process. When they compared their reconstructions, they found they had independently reached essentially the same conclusions about how the parts fit together.

Another co-director of the project is Berhane Asfaw Ph.D. ’88 who also was a protégée of Tim White. The first Ethiopian to receive a doctorate from an American university, Asfaw, who has several major fossil finds to his credit, has been part of the project since 1981, and is a former director of the National Museum of Ethiopia.

“When” is always a vital question with fossils, and Paul Renne ’82 Ph.D. ’87 the founding director of the Berkeley Geochronology Center, helped answer that for the Ardi remains, with argon-argon dating and paleomagnetic dating.

THE “TARGET ORGANISM” of anthropology has always been the human being, and that’s true of its subset, paleoanthropology, as well. But the landscape has changed. In the early days, the “stones and bones” stereotype was somewhat accurate. But now the Study of Man flows freely across the intersection of the biological sciences, the physical sciences, and the social sciences.

Tim White said in a 2003 interview, “The popular concept is that somebody rides out on a camel, looks off the camel, and says, ‘There’s a skull. Let’s take it back and write a book!’ Maybe it happened like that a long time ago, but not anymore. These are very large projects.”

Team member Leslea Hlusko says the Ardi package of research is “a wonderful example of the inter- and multi-disciplinary nature of modern paleontology” and that “no one individual could ever hope to be able to master all of these research areas.” She advises a budding paleontologist or paleoanthropologist to see the field as “one in which you build collaborations at multiple levels,” with scientific teammates, host governments, and so on. You also need, she says, to build a broad knowledge base, including “a strong understanding of geology, anatomy, evolutionary theory, and genetics, to list just a few.”

Proving the romance of fieldwork is not totally dead, Hlusko adds, “You will also want to know how to drive a stick-shift, change a tire, shower with just one liter of water — when you can get it — and, of course, identify poisonous snakes.”

— article by Dick Cortén (originally published in The Graduate magazine, Spring 2010)