In the News: On the Trail of a Few More Ancestors

http://www.nytimes.com/2001/04/08/science/08FOSS.html

April 8, 2001

On the Trail of a Few More Ancestors

by John Noble Wilford

Fossils of what may be the earliest known ancestor of the human family have been unearthed in Kenya. The bones and teeth are about 6 million years old, at least 1.5 million years earlier than any similar finds, and so their discovery could be a major advance shaking up the human family tree yet again.

They are already shaking up the family of paleontologists. As details emerged in recent weeks, the age of the fossils was the only aspect that seemed beyond dispute. To assertions by the discoverers that the individual mostly walked upright and was a direct ancestor of modern humans, many prominent scientists have reacted with head- shaking skepticism bordering on disbelief.

These critics think the fossils are more likely to be of a chimpanzee or one of its ancestors. This in itself would be a significant find because the early fossil record of chimpanzees, the nearest relatives to humans, is barren.

But some researchers suspect the growing controversy may be fueled in part by personal animosities and territorial disputes. One of the discoverers, Dr. Martin Pickford of the College de France, has made important enemies in his profession, notably Richard Leakey of the Kenyan fossil-hunting family. Others among Dr. Pickford's critics suggested the newly found fossils might have been collected illegally on the turf of another paleontologist. On Friday, Dr. Pickford and Dr. Brigitte Senut, an anatomist at the National Museum of Natural History in Paris, denied the charge of digging without a permit and said that most of the scientific criticism was coming from paleontologists who had not seen the original fossils or even casts of them.

"The newly discovered material probably troubles the established scenario about human evolution and especially evolution of bipedalism," Dr. Senut said in an e-mail message from Paris. "Our findings have been unfairly judged by a few colleagues."

If the discoverers are correct, the fossils represent a hominid of an entirely new genus and species, which has been named Orrorin tugenensis. Orrorin means "original man" in the local dialect. At an age of 6 million years, it could be one of the first hominids living after their split from other lineages leading to apes.

In a journal of the French Academy of Sciences, Dr. Senut and Dr. Pickford, a paleontologist, reported that partial remains of thigh bones bore signs suggesting that the creature "was already adapted to habitual or perhaps even obligate bipedalism when on the ground, but that it was also a good climber."

Bipedality, walking upright on two legs, is considered a defining characteristic of hominids, so whether Orrorin could do so is the point of sharpest dispute among scientists. Their conclusion that it could, as well as the fact that its teeth were smaller than those of apes and many other subsequent hominids, persuaded Dr. Senut and Dr. Pickford that Orrorin stood on a direct line leading to modern humans, bypassing intermediate groups such as Australopithecus afarensis, best known by the 3.2 million-year-old Lucy skeleton found in Ethiopia in 1974.

The story of early human origins has already been thrown into confusion by a discovery announced last month by Dr. Meave G. Leakey, a paleontologist and the wife of Richard E. Leakey. She reported finding in Kenya the 3.5-million-year-old skull and other fossils of another new genus and species, Kenyanthropus platyops. The skull also appeared to push Lucy off to a side branch of the family tree, Dr. Leakey said. Her interpretation was generally greeted with peer approval, unlike the Senut- Pickford find. In a carefully worded response, Dr. Leslie C. Aiello and Dr. Mark Collard, paleontologists of University College London, wrote in the journal Nature that the sediments where the Orrorin fossils were excavated, in the Tungen Hills northwest of Nairobi, had been thoroughly studied before and were established to have been laid down about six million years ago.

The oldest previously recognized member of the hominid lineage is Ardipithecus ramidus, based on 4.5- million-year-old specimens collected in Ethiopia. It is not yet clear whether this species walked upright. Dr. Senut and Dr. Pickford contend that Ardipithecus was more likely an ancestor of African apes than of humans. They also cast most australopithecines out of the human ancestral line.

Of the 12 fossils in the new collection, fragments of the upper parts of femurs, or thigh bones, have received the closest attention. The discoverers maintain that the head of the bone is large and humanlike in relation to the size of the neck of the bone. This and other characteristics, they argue, supports the conclusion that this species was bipedal.

But Dr. Alan Walker, an anatomist at Pennsylvania State University who has often excavated with the Leakeys, said he was "not impressed with their evidence" for bipedality of the species. Evidence from the lower end of the femur would have been more convincing, he said, but that was missing, and other cited evidence could have contradictory interpretations. "If Orrorin was not bipedal then neither was Lucy, and we have to go back to the drawing board," Dr. Pickford responded. "In many ways, the Orrorin femur is closer to those of modern humans than they are to Lucy's, and they are quite different from those of chimps."

Dr. Daniel E. Lieberman, a George Washington University paleontologist, said: "I swear the fossils are so chimpanzeelike that it's incredible. If it were a chimpanzee, it would be the first record we have of their early evolution."

Although he said the discoverers were competent researchers, Dr. Milford Wolpoff of the University of Michigan complained of the "low density of information, not enough to be claiming all this."

Dr. Andrew Hill, a Yale paleontologist, said he had conducted excavations near the discovery site for more than two decades and still had a legitimate permit that covered the land where the Orrorin fossils were found. He said Dr. Pickford had encroached on his territory by sidestepping usual channels to obtain a permit to work the same land.

Dr. Pickford said he had a research permit that was issued in 1998 by the office of President Daniel arap Moi of Kenya, and it was valid through Dec. 31, 2001. The fossils in question were collected last year. His sponsoring institution was the Community Museums of Kenya, which he had helped found. Previously, all permits were granted through the National Museums of Kenya, where Dr. Meave Leakey is the principal paleontologist and her husband was director for a long time.

Several scientists suggested that personal animosities might be behind much of the controversy. Dr. Pickford and Mr. Leakey once worked together, but had a falling- out that became public in 1985 when Dr. Pickford was barred from the national museum. Eventually, Dr. Pickford co-wrote a book, Richard E. Leakey: Master of Deceit.

In March last year, Dr. Pickford was arrested on charges of collecting fossils without a permit and spent five days in a Kenyan jail. Now he has sued Mr. Leakey, among others, alleging unlawful arrest and malicious harassment.

The debate would probably be equally intense on a scientific level because, paleontologists said, so much - such as claims of finding the earliest known human ancestor - is being made of a modest, though fascinating, collection of fossils. Everyone seemed to expect the dispute to last for months, even years.