Bones of contention

On the morning of June 10, beneath the glare of reporters and television lights, in a subterranean classroom at the University of California, Berkeley, two anthropology professors spilled onto a cerulean blue tabletop their fragile fossils from a maroon pouch. One was a skull fragment, the other a partial thighbone, both radiometrically dated at between 3.9 and 4.1 million years old.

The bones, unearthed last fall during an expedition to the Horn of Africa, are the oldest known remains of early man. According to Tim White, the team's head paleontologist, the fossils put anthropologists hot on the trail of ''the last great missing link'' in the controversial evolutionary chain between apes and the family of man.

To untrained eyes, the new fossils looked like something you might toss Fido under the supper table; to the anthropologist, however, these are serious bones of contention. The new evidence of humankind's origins does nothing less than challenge generations of the legendary Leakey family's research in East Africa, and contradict some of Darwin's most time-honored assumptions.

Scientists say the fossils, found in north-central Ethiopia, shed important light on three major debates in the field of anthropology today:

1. Does evolution occur as Darwin predicted, in a gradual, continuous progression of increasingly complex descendents? Or does it look, as suggested recently, more like a series of plateaus ''punctuated'' with quantum leaps in development caused by responses to catastrophic changes in the environment?

2. How old is man? When and why did he stand upright?

3. Did man first develop his erect posture, and only relatively recently take on the intellectual and technological traits associated with human beings? Or is there, as postulated by Darwin and later the Leakeys, a ''true man,'' genus Homo , who simultaneously developed upright walking with a greater intellectual capacity and the use of stone tools?

On the best of days, paleoanthropologists are pick-and-hammer detectives sleuthing the alleys of prehistory. On the worst of days, they are blind men describing an elephant.

Not long ago one scientist suggested that sketching the course of human evolution from the spotty fossil record was ''rather like trying to follow the story of 'War and Peace' from 12 pages torn at random from the book.'' Clues to our remote forebears are rare; the entire collection of significant hominid fossils - zoologically relating to the human family - from the last 4 million years would not cover a picnic table. That is why the discovery of each new bit of old bone is cause for celebration, controversy, and a press conference.

One of those press conferences was held in 1974. It was then that Donald Johanson, one of Tim White's former colleagues at the Cleveland Museum of Natural History, discovered the now-famous 3.6 million-year-old partial skeleton of an upright-walking, small-brained ape-woman at Hadar, Ethiopia. Before ''Lucy'' (as the skeleton was dubbed after the popular Beatles song ''Lucy in the Sky With Diamonds''), conventional anthropological wisdom held that earliest man developed his erect stance simultaneously with an expanded intelligence and use of tools.

The new fossils, retrieved from the remote Middle Awash River region in Ethiopia's Afar Triangle, lend crucial support to Johanson and White's controversial theory. They believe that a species called Australopithecus afarensis (the ''Afar ape-man'') rose on its hind legs millions of years before it started using tools. (Johanson recently founded the Institute of Human Origins near the UC Berkeley campus, where White is now an assistant professor of anthropology.) The bones from the Awash are thought to have belonged to a 4 1 /2-foot-tall, two-legged creature with a chimpanzee-size brain. The skull fragment is twice as old as the famous finds by the Leakey family at Koobi Fora in Kenya and Olduvai Gorge in Tanzania. The thighbone is proof that Lucy walked the plains of Africa as upright as modern man does today.

This controversy, and others, may be resolved once and for all when the seven-nation team returns this September to the Awash, an area that many anthropologists call ''the most significant hunting ground for prehuman fossils ever discovered.'' The Awash, 125 miles from the fighting in the Ogaden and Eritrean regions, has been closed to scientific exploration. Last December's expedition was the first group in five years that the Ethiopian government had invited to study the fossil-rich riverbed.

The first debate, over the theory of human origins, begins with Charles Darwin, the grandfather of gradualism. His theory that evolution plodded along in a slow, steady, uphill march was essentially fossil-free. When he wrote ''The Origin of Species,'' no hominid fossil record existed. In fact, the publication of ''Origin'' 120 years ago coincided with the discovery of the first fossil evidence of early man, the skeletal remains of Neanderthal man found by limestone quarrymen outside Dusseldorf, Germany. Though it has proved surprisingly durable, Darwin's great theoretical cathedral was constructed with shaky scaffolding and scant materials.

When paleontologists began to uncover fossils indicating evolution might not be a graded incline but rather a series of evolutionary jumps, Darwin argued these gaps in the fossil record were only gaps in the geological record. Sooner or later, he protested, scientists would find the ''missing links'' in the fossils and vindicate his theory.

In the last decade, two paleontologists, Steven Jay Gould at Harvard's Museum of Comparative Zoology and Niles Eldredge at the American Museum of Natural History, have resurrected and popularized the critique of Darwin. Their ''punctuated equilibrium'' picture describes evolution as a series of long-lasting stable species which adapt quickly (in geological terms) to drastic environmental changes.

The dense hominid fossil record at Awash, White maintains, could recast the squabble between Gould and the neo-Darwinians. So far, White told the Monitor, Awash has provided evidence of both gradual and punctuated patterns of evolution. ''The new 4 million-year-old hominid fossils,'' he said, ''together with the 3.6 million-year-old Lucy, suggest what looks like a stable, ecologically diverse, species.''

''The other part of fossil record,'' he added, ''is 'Bodo man.' '' In 1976 American geologist Jon Kalb visited the Awash area and discovered the 300,000 -year-old partial skull of an early human at a site called Bodo. Physiologically it resembled an individual somewhere between Homo erectus (upright man) and Homo sapiens (wise man), thereby lending credence to the gradualists. ''('Bodo man') appears to be an intermediate form, suggesting a gradual expansion of the brain and reduction of the face. Given the evidence at Awash,'' White said, ''evolution could have gone either way.'' That is, gradually or in ''punctuated'' jumps.

In the second arena of controversy, as to when the great apes and man parted company, the Awash fossils have pushed that date back another half million years , from 3.6 million to 4 million years ago. At the moment it is impossible to pinpoint the split because of the vast gap in the fossil record between the new Awash hominid fossils at 4 million years and the great ape fossils of Java, dated at around 17 million years.

Allan Wilson and Vincent Sarrich, two molecular biologists at Berkeley, now estimated that the split occurred between 5 million and 6 million years ago. Meanwhile, geologists at the Awash site have found rocks that are more than 6 million years old. Given those findings, the team that will return to the Awash feels it has within its grasp the coveted possibility of unearthing the ''last great missing link,'' which anthroplogists have sought for decades.

The third controversy, over the simultaneity of upright walking with greater intelligence and the use of stone tools, was touched off by Lucy in 1974 and reignited last month with the Awash fossils. When Johanson said that Lucy was part of a new species, A. afarensis, and that members of that species were direct ancestors of humans today, he came under harsh and immediate fire, particularly from the Leakey family.

The late Louis Leakey, the Kenyan missionaries' son, who became a legendary anthroplogist, believed that the hominid line that eventually leads to modern man branched from the apes 20 million years ago. At the time, he held, the creature was bipedal (upright walking), and simultaneously used the stone weapons he needed to defend himself when he came down out of the trees.

Louis's wife, Mary, and son, Richard, now both living in East Africa, have defended Louis Leakey's work and believe that genus Homo, ''true man,'' is quite ancient, and perhaps coexisted with Lucy and her relatives. The Leakeys claim Lucy is not an ancestor to modern man at all, but an aberration, a dead end in the evolutionary chain.

Tim White worked for years with the Leakeys in East Africa, but now he believes they are barking up the wrong tree. ''According to the Leakeys' belief, as we go into the rocks of 4, 5, 6 million years ago (at Awash) we should find 'true man,' bipedal, with an enlarged brain and the advent of technology. But the new fossils (from Awash) have taken us back another 400,000 years before Lucy, and there is still no evidence that the Leakeys' 'true man' ever existed. The Leakeys argue not from evidence and theory, but belief and family tradition. The new fossils don't totally disprove the Leakeys, but the possibility that we'll find 'true man' (at Awash) is unlikely.''

Heading the historic Awash expedition is J. Desmond Clark, a UC-Berkeley anthropology professor considered the world's foremost authority on African prehistory. Clark, an Englishman with a ruddy face and a white goatee, wears brown corduroy jackets with academically worn elbows. He carries a carved African walking stick and uses it as a pointer in lectures. Clark earned his anthropology degree from Cambridge University, in 1938 and spent the next four decades trudging across the African continent in search of clues to the origins of humankind. (Clark raced for his university at Henley, a tradition he proudly says he continued on the rivers in Africa. Rowing against Oxford was child's play next to circumnavigating hippos on the Zambezi.)

For 42 years Clark hunted high and low and then last year stumbled onto the treasure-trove at Awash. He proclaimed: ''This area is likely to be the key to providing answers we are all looking for in searching for the origins of humanity and the cultural behavior that made us what we are today.''

Some 215 miles from Addis Ababa by Land-Rover is the Middle Awash. It's a desolate, desert region that crouches at the northern end of the Great Rift Valley, which many paleontologists call the ''cradle of humankind.'' The Middle Awash is just 45 miles south of Hadar, where Johanson found Lucy. Because of the rapid burial of artifacts by rising lakes and falling volcanic ash at Awash over the years, the fossils have been well preserved and offer important windows into the world's prehistory. Clark calls Awash ''a gigantic sink into which 6 million years' of sediment has conveniently collected.'' The valley is ribboned with geological ''horizons'' of volcanic lava and ash, easily dated through radiometric analysis and useful in calibrating of the region's evolution.

In two brief months of surveying, Clark's team turned up not only the headline-grabbing hominid fossils but also a wealth of prehistoric tools, some dating back 1.5 million years, and animal footprints going back 6 million years. Entire hillsides on the east bank of the Awash are strewn with ancient hand axes , choppers, scrapers, and other stone tools used by Homo erectus. ''The ground is littered with fossils,'' White said. ''We've found everything from the skull of a shrew and some crocodile eggs to a 4 million-year-old elephant jaw. In some places you literally cannot take a step without stepping on a fossil.''