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Oldest ape-man skeleton may hint where paths split S. African discovery is 3.5 million-year-old evolutionary evidence


JOHANNESBURG, South Africa -- One day, about 3.5 million years ago, a small ape-man walking through the rain forests fell to his death down a 45-foot-deep cave shaft near here, setting the scene for yesterday's announcement of one of the most dramatic anthropological discoveries ever made.

Almost the entire skeleton and skull of the 4-foot-tall hominid -- or member of the family of mankind -- has been found in the cave at Sterkfontein. It may be the oldest complete skeleton of an ancient ape-man unearthed anywhere.

"Probably it is the most momentous paleo-anthropological find ever made in Africa," said Phillip Tobias, professor emeritus of the anatomical sciences department at Witwatersrand University.

It promises to reveal many of the major mysteries of early human development as man and apes went their separate ways. It takes scientists a step closer to discovering the "missing link," the common ancestor of the two species.

"We are getting down, nearer and nearer to the parting of the ways between the hominids and the African apes, which shared with us a common ancestor perhaps 5 to 7 million years ago," said Tobias.

Hominid remains dating as far back as 4.5 million years have been found in Eastern Africa, but they have been only fragments. The oldest, complete skeleton previously unearthed was "Lucy," who lived in Ethiopia 3.2 million years ago.

The new fossil has not been named, because it is not known whether it was male or female. It simply has a catalog number: StW573.

Most of the skeleton lies encased in the rock and limestone in Silberberg Grotto, one of the darkest, most damp areas in the cavern.

Ron Clarke, the paleo-anthropologist with Witwatersrand who made the find, said: "This will contribute so much information to the search for the history of our ancestry, to go back to the very earliest period when we were developing from the ape and to find out how that happened."

The discovery literally followed the old lyrics of the toe bone being connected to the ankle bone, the ankle bone being connected to the knee bone.

Three years ago, Clarke, rummaging around in storage boxes of fossils collected from debris at Sterkfontein after lime workers blasted the cavern in the 1920s and 1930s, spotted some tiny hominid foot bones with both apelike and human characteristics.

The small creature had developed a heel for walking upright on the ground but had the flexible big toe of the chimpanzee for tree climbing. It was dubbed "Little Foot."

A closer look

Last year, he decided to re-examine the StW573 remains. Opening the cupboard he noticed a box containing fossils of an extinct type of hunting hyena, which had been found in the Silberberg Grotto. He decided to study them.

In the first plastic bag he extracted, he noticed a telltale white hominid bone. It fitted exactly one of the foot bones he had found two years earlier. In other bags he found more bones, giving him 12 lower-leg, shin and foot bones, all apparently from the same skeleton.

Knowing that African carnivores frequently eat the legs and feet first, he was convinced that the hominid had not been attacked and that the rest of the skeleton must be in the grotto.

He gave a cast of a fragment of one of the broken leg bones to two archaeological diggers, and asked them to search for a matching piece sticking out of the floor, ceiling or walls of the grotto.

"It was very dark, very wet," said Stephen Motsumi, one of the assistants. "We had little brushes to brush any white spots we thought were fossils."

On the second day of the search, he noticed a small white patch, shone his hand-held light on it and tried to fit the cast to the piece of bone sticking out of the lower edge of the slope.

"It fit perfectly," said Motsumi. "I couldn't believe it."

Using hammers and chisels, Clarke and his two assistants spent months working their way along the length of leg as far as the broken thigh bones. Then, mysteriously, there was nothing.

"The rest of the skeleton ought to be there," Clarke recalled thinking. "But where is it?"

For months, the three scraped and chiseled in vain. "I was at the point of despair," Clarke recalled yesterday. "I told myself it had to be there. Logic demands it ought to be there."

Then he noticed signs of ground displacement in the cave and realized the floor had collapsed, breaking the skeleton and carrying the missing part deeper into the cavern. He told the assistants to start digging and call him at home if they found any bones.

The next day, Motsumi phoned to say: "We have got something."

It was the lower jawbone. As Clarke chipped away, he saw the gleam of enamel.

He remembers shouting: "There it is. But good Lord, this is not a lower tooth, it's an upper tooth. We have got the whole skull."

Slowly the cheekbone, forehead and brain case were uncovered. It will take at least a year to complete the excavation and analysis of the bones.

The creature has been identified as an Australopithecus, or southern ape-man, fossil remains of which were first found at Sterkfontein in 1936. Its precise species has not been established. It could turn out to be a new species.

'Tuang Child' surpassed

The find eclipses the 1924 discovery of the upper and lower jaw of "Tuang Child," the first Australopithecus fossil found in South Africa and previously regarded as the most important find in this country.

"Just one bone would be exciting, but this is apparently the whole skeleton -- the secret to knowing how the creature functioned," said Tobias, who started excavating at Sterkfontein years ago.

The skeleton will show how adapted StW573 was to walking upright on two feet as opposed to the four-limb movement of apes, and might help solve the puzzle of why hominids came down from the trees.

"Maybe one of the periodic drying-up periods in Africa was thinning out the trees, and as a result they were a bit crowded, " said Tobias. "Perhaps it was a change of feeding habits."

How it came to fall down the shaft is not known.

"Finding a complete skeleton like this means it was not killed by carnivores," said Clarke. "It may have fallen in when he or she was being chased by carnivores. Or it may have been accidental. We can't really say.

"This story, like every good detective story, begins with a death."

Pub Date: 12/10/98

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