Thursday, December 10, 1998    

    Skeleton Gives Glimpse of Human Roots
    By ROBERT LEE HOTZ, Times Science Writer

The earliest known complete skeleton of a human ancestor is emerging from the stubborn rock of a limestone cave in South Africa, offering an unprecedented look at the brain size, body proportions and walking abilities of early humankind, scientists announced Wednesday.

Several experts familiar with the skeleton—perhaps 2 million years older than any other complete hominid find—called the discovery a “fantastic breakthrough” that should offer the best look yet at whether early humankind lived in trees while also walking upright.

In research published in the South African Journal of Science, Ron Clarke, a paleoanthropologist at the University of Witwatersrand, announced that he had found a skull, limbs and torso—much of them still embedded in the hard travertine and dolomite deep within a cave at Sterkfontein near Johannesburg.

Found at one of the world's richest fossil sites, the bones belong to a small, adult creature about 4 feet tall and weighing perhaps 70 pounds that appear to date from 3.2 million to 3.6 million years ago, the scientists said. They said they were not yet sure what species of ancient human the bones represent.

The oldest complete skeleton before this latest discovery belonged to a member of a younger species called Homo erectus found in Kenya, dating to 1.5 million years ago. Older hominid fossils have since been found in Kenya, where anthropologist Meave Leakey recently discovered a 4.2-million-year-old Australopithecus afarensis, but those remains were fragmentary.

“If this is a complete skeleton, this is pretty spectacular,” said Philip Rightmire, an expert on human origins at the State University of New York at Binghamton.

Anthropologist Henry McHenry at UC Davis, who has studied the early human fossils previously unearthed in the Sterkfontein caverns, said: “This is a triumph. It is the whole skull. You can see the teeth and the jaw and the rest of the body is there. It is fantastic—more complete than Lucy, even.” (Lucy is the popular name given to the partial skeleton of an early human species discovered in Ethiopia in 1974.)

Yale University expert Andrew Hill, curator for anthropology at the Peabody Museum, emphasized the importance of finding so many fossil bones that belonged to one individual. “To have an integrated skeleton is really, really great — whatever particular species it may turn out to be. If you only have isolated bones, you don't know how they functioned together in an individual.”

On display are the fossilized jawbone, right, of hunting hyena alongside a replica of a foot of the oldest complete skeleton of a human ancestor which were found at an excavation site, shown in background, at the Sterkfontein caves outside Johannesburg, South Africa. -Associated Press

Certainly, there has been no shortage in recent years of fossil skull fragments, teeth, bits of limbs, sets of vertebrae and ribs, and a few pelvises of these ancient creatures for scientists to study.

But without being able to actually see how the bones all fit together in one skeleton, researchers have been unable to answer fundamental questions about the size of the early human brain in relation to the size of the body, the creature's probable diet, how it moved and other biomechanical mysteries.

Dr. Ron Clarke of the University of the Witwatersrand holds a three and half million years old Australopithecus bone.

More than any other characteristic such as brain size or the use of tools, the ability to walk on two legs has become the defining moment in the history of human evolution. And, for that reason alone, these fossils have the experts excited.

For the first time, they will be able to match foot bones to knee joints to hip structure and the rest of a hominid skeleton to better understand how these earliest humans moved through the woods and plains they inhabited.

“Walking upright—bipedal locomotion—is the hallmark of our lineage,” Rightmire said. “It is important to know when that lineage branched off from something more like African chimpanzees.”

Unlike many fossil finds, this discovery began indoors. In September 1994, Clarke started rummaging through boxes of unsorted fossil fragments blasted out of the cavern by stoneworkers who had used the area as a limestone quarry in the 1920s.

To his astonishment, he quickly found the unmistakable pieces of a hominid left foot. A search of more boxes and bags of fragments in storage turned up a total of 12 foot and lower leg bones clearly belonging to one individual.

With their combination of apelike and more human characteristics, the fossils, which came to be known as "Little Foot," quickly became the center of an international debate over when and how humans started to walk upright.

As scholars argued over the meaning of the foot bones, Clarke continued to search more boxes and found even more foot bones from the same creature.

By then, he was convinced he could find the rest of the skeleton in the cavern. Starting in June, he had workers scouring the cavern walls for the bones. “The task . . . was like looking for a needle in a haystack, as the grotto is an enormous deep, dark cavern, with breccia exposed on the walls, floor and ceiling,” Clarke said.

Even so, within days, the crew found a piece of fossil leg bone sticking out of the wall that exactly matched a fragment from the boxes.

The skeleton of the three and one-half million-year-old Australopithecus recently discovered in the Sterkfontein Caves near Krugersdorp, South Africa, according to scientists.

Crew Finds Rest of Creature's Skeleton

“The fit was perfect, despite the bone having been blasted apart by lime workers 65 or more years ago,” Clarke said. “From their positions with the lower limbs in correct anatomical relationship, it seemed that the whole skeleton had to be there, lying face-downwards.”

After weeks of anxious quarrying, Clarke and his crew discovered the creature's skull and the rest of its bones embedded in what appeared to be the stratified remains of an ancient rock fall.

Clarke was reluctant to say whether the individual was male or female until the workers have carefully extracted the skull—a task expected to take a year—and the rest of the bones.

Although the scientists are not yet sure what pre-human species the bones represent, they are certain that the remains constitute a much more complete skeleton than that of the famous Lucy, who lived and died in Ethiopia at roughly the same period of time.

The new find might belong to Lucy's species, called Australopithecus afarensis, or to a different species of a slightly younger vintage called Australopithecus africanus, whose fossilized remains have been found in the same caves since the 1930s. Those finds date from about 2.6 million years ago.

Based on animal fossils found in the same rock layers as the bones, Clarke and his colleagues concluded that the new skeleton was as much as 3.6 million years old.

Several experts, however, cautioned that the fossils may turn out to be much younger.

Unlike other areas of Africa that have yielded important human fossils, it is very difficult to date any find in South Africa with precision, experts said. Most advanced radiometric dating techniques require volcanic ash or material from ancient lava flows to determine exact age. There are no volcanic deposits in the region.

“The major question is antiquity,” said Donald Johanson, director of the Institute of Human Origins at Arizona State University, who discovered Lucy. “It may very well be that it is a million years younger than they say.”

“That should not overshadow the remarkable importance of a complete specimen like this, so we can really define what a hominid looks like,” Johanson said.

Copyright Los Angeles Times

 Related Sites 

Fossil Hominids [FAQ]    The Talk Origins    Donald Johanson    Discover Magazine

Human Evolution: The Fossil Evidence in 3D BBC RealVideo Report Scientific American Site News Index