Africa’s ‘Grand Canyon of Human Evolution’ May Hold More Secrets

In the decades since a preoccupied German butterfly collector almost tumbled headlong into Olduvai Gorge, this gash in Africa’s Serengeti Plains has become known as the Grand Canyon of human evolution.

Other sites have yielded more fossils than Olduvai, but none “has produced the concentration of archeological material, cultural material, that Olduvai has produced,” said Tim White, a paleontologist at the University of California, Berkeley.

Donald Johanson, director of the Institute of Human Origins in Berkeley, said: “Here you have definitive association between stone tools, animal bones and early hominids in a very well-understood environment.”

Heads Research Project

Johanson is leading a new and enlarged research program at Olduvai in cooperation with the Tanzanian government. The effort resulted in a major find almost as soon as it began in the summer of 1986, suggesting that the gorge has many secrets yet to divulge.

Johanson is to explore the ravine and train Tanzanian paleontologists.

“It’s a marvelous, exciting place,” said Richard Hay of the University of Illinois in Urbana, who did the definitive research on Olduvai’s geology. “It has had a very important catalytic influence on research elsewhere and in developing our present-day notions of our family tree.”

But the findings at Olduvai have often confounded paleontologists and provoked lively debate, such as the 1986 discovery of a 1.8-million-year-old skull and partial skeleton of a woman with surprisingly long, apelike arms.

‘Something Extraordinary’

“It tells us something extraordinary, something we’ve never anticipated before,” Johanson said recently. “It must suggest that natural selection was keeping those arms long.” The creatures, he said, “were probably participating in some degree of tree climbing.”

But Milford Wolpoff, an anthropologist at the University of Michigan, said the hominids may have had long arms for other reasons. “Maybe swinging clubs makes good sense as well.”

“I think the question of climbing trees can be handled when there’s a good enough analysis of the shoulder,” Wolpoff said. “This shouldn’t be speculation. Somebody should be able to show they were climbing trees or they (were) not.”

Johanson and White say their find represents the species Homo habilis , the first toolmakers.

Collection Too Diverse

But Bernard Wood of Liverpool University in England has pointed out that the collection of skeletons identified as Homo habilis may be too different from one another to be grouped together.

Once again, Olduvai has challenged widely held notions about human evolution.

Olduvai Gorge lies in northeastern Tanzania, 100 miles west of Mt. Kilimanjaro and the same distance south of the Kenyan border. It cuts across a corner of the Serengeti Plains, inhabited only by vast herds of migrating animals and roving bands of Masai tribesmen.

Olduvai is a corruption of the Masai words for “the place of the wild sisal,” a reference to the cactus-like plants scattered on Olduvai’s slopes.

Lions, leopards and cobras roam the gorge. Its red, brown and gray soils are littered with bones, primitive stone tools and the stone flakes that have been chipped off them.

“There are places you can’t walk without stepping on a stone flake,” White said.

Smaller Than Grand Canyon

The Y-shaped gorge is 25 miles long and 300 feet deep, much smaller than the Grand Canyon. It is green during the rains of spring and fall, parched in summer and winter. And its elevation on the Serengeti makes it cooler than other East African fossil sites.

“It can get hot, but when one compares it to Koobi Fora in Kenya or the Lucy site in Ethiopia, it’s Club Med,” White said.

Olduvai developed 500,000 years ago when two streams met and began slowly to slice into the Serengeti’s earth. Climate and geography conspired to direct the streams across an ancient oasis where, 2 million years ago, a fresh river emptied into an alkaline lake.

Roving groups of hominids--early humans, their human-like ancestors and extinct cousins--gathered there, ate there and died there, leaving their remains first to be covered by time and then uncovered by the eroding action of water against rock.

Volcanoes Helped

A cluster of nearby volcanoes that are now extinct periodically dusted the ground with whitish ash that has, by chance, allowed precise dating of Olduvai’s sediments.

“You can stand on the bedrock and gaze at millennium after millennium, stacked neatly as a layer cake,” wrote Richard Leakey, an anthropologist and the son of Louis Leakey, who made Olduvai famous.

Sixty-two skeletons of hominids have been uncovered at Olduvai, skeletons that would not have been found if the streams that formed the gorge had meandered even a few miles away from the prehistoric lakeside oasis.

Louis Leakey was the first to extensively explore the gorge, beginning in 1931. He used to tell of the adventures of a certain professor Kattwinkel, a German lepidopterist, who was pursuing some exotic butterfly across the Serengeti when he ran headlong into the gorge.

Recovering his bearings, Kattwinkel hiked into Olduvai and came back with several fossil bones.

Leakey’s expeditions later accumulated a large collection of primitive stone tools. But by the 1950s he had still not found what he sought: the remains of the makers of the tools.

Skull Spotted

On July 17, 1959, Leakey, recovering from the flu, was too weak to leave camp at Olduvai. At 11 that morning, his wife, Mary, saw a skull on a slope where stone tools had been found in 1931.

A tiny stone monument now marks that spot. The Leakeys named the skull Zinjanthropus, and it became one of the most famous fossils ever known.

The classification of the skull immediately became a matter of debate, and experts argued over whether this was indeed Leakey’s toolmaker or whether it was the skull of a creature too primitive to have constructed tools.

Mary Leakey continued to study Olduvai through the 1960s, as Louis gradually withdrew from field work. Fossils and stone tool remnants have been found at 127 sites along the length of the gorge, according to John Reader, the author of “Missing Links,” a history of paleontology.

Finishing Her Writings

Mary retired a few years ago and moved to Nairobi to complete her writings, and research at Olduvai nearly stopped.

Donald Johanson was in high school when he learned about Zinjanthropus. “I remember a neighbor bringing over a National Geographic,” he said.

Two years ago, he approached the Tanzanian government about establishing a new research program at Olduvai.

Johanson and White made their first collecting trip to Olduvai last year. Their team included Prosper Ndessokia, a Tanzanian graduate student at UC Berkeley, and Fidelis Masao of the National Museums of Tanzania in Dar es Salaam.

Late on the afternoon of their third day there, when the sun had descended below the rim of the gorge, leaving it in shadow, White spotted some bones on the ground near a small rise called Dik Dik Hill.

‘We’ve Got a Hominid’

He picked one up. “I said to Johanson, ‘We’ve got a hominid here,’ ” White recalled. It was the upper end of the ulna, an arm bone.

Moments later, a graduate student with White and Johanson said: “I think I’ve got a maxilla (upper jaw bone) here.” It was becoming clear that the find could be important.

“Right away we got off the site,” White said. “We were in shadow, and the more people you have walking around, the more churning you have of fossils into the soft ground.”

White’s first thought was that he could now answer the skeptics who had told him that Olduvai was exhausted, that it had been studied so extensively that nothing remained to be found.

Plans to conduct various surveys of the gorge were scrapped to focus efforts on properly excavating the specimen. One month later, after all the soil from an area about 30 yards by 60 yards had been removed, examined and filtered through window screen, the researchers had discovered 18,000 pieces of bone.

‘Backbreaking Work’

“It’s really backbreaking work,” White said. “But the nice thing was that every day we would get another little piece we could identify that would spur us on.”

Along with the hominid skeleton were bits of elephant, antelope, porcupine, snake and tortoise that had to be separated and identified.

Reconstruction of the jaw bone alone required the assembly of 30 bone fragments, White said.

White concluded that the skeleton had been exposed for centuries. “That’s probably why no one had spotted it--it was very broken up,” he said.

Since the skeleton was found to be about 1.8 million years old, it indicated that apelike arms persisted among the ancestors of humans much later than many had thought. By 1.6 million years ago, hominids had proportions similar to today’s Homo sapiens .

What happened to change our ancestors so dramatically in such a relatively short period? Continuing excavations at Olduvai may help explain that, as they reveal more of humanity’s dim past.

As one English paleontologist has said of his explorations there: “For every day, there was something new. Small things, most of them, but always of surpassing interest.”