Sifting through a bag of discarded animal fossils last year, Ronald Clarke came across something decidedly human and possibly historic.
The find: a foot bone that Clarke says shows humans spent part of their evolution from apes walking upright like men and climbing trees like monkeys.
The question of whether human ancestors ever lived in trees has for years sown division among paleontologists. Some say man evolved from a plains-dwelling species that walked upright, while others, like Clarke and University of the Witwatersrand colleague Phillip Tobias, contend ape-like ancestors walked on ground and climbed trees. The two men say Clarke’s discovery is the firmest evidence to surface in years supporting their position.
At a news conference Friday complete with fossil bones and plaster casts of human and ape feet, they said their find proved an ape-man known as Australopithecus had both human and apelike features.
In particular, they said the foot bones showed the ape-man that lived an estimated 3.5 million years ago could walk upright like man but had an apelike big toe capable of grasping and more movement than a human big toe.
“The ankle bone was perfectly human,” Tobias said. “But as we traveled toward the big toe, more and more chimpanzee features appeared.”
An article by Tobias and Clarke appeared in Friday’s edition of Science, the authoritative weekly journal of the American Association for the Advancement of Science in Washington.
New arguments came with their publication. An accompanying article in Science by Owen Lovejoy of Kent State University in the United States rejected the Clarke-Tobias conclusion. Lovejoy said Tobias and Clarke ignored other research that indicated ape-men walked upright, according to the bone structure of their hips and spine.
But Tobias said an unassailable body of evidence now existed to support his and Clarke’s position. Other findings showed the ape-man’s knees and shoulders retained apelike features good for climbing, he noted.
“Australopithecus was far more apelike in many of its features than we’d ever dared imagine previously,” he said.
It was unclear which species of Australopithecus the four foot bones belonged to, Tobias said. Two species, determined by teeth and other features, have been found in South Africa, while at least two others were discovered in east Africa in the famous finds of Tanzania and Ethiopia by Louis and Mary Leakey and others.
How Clarke discovered the fossils also was a bit inexact. The stones that contained the new find were from a deep layer estimated to be 3.5 million years old at Sterkfontein caves northwest of Johannesburg.
In the 1920s, part of the layer was blasted out and the refuse rock was left lying underground. Eventually it was collected and brought to the surface, but the four foot bones didn’t turn up in processing.
Clarke was perusing some bags of the discarded fossils last year for evidence of animal life from the early era. It was then he found a piece of human ankle bone, then three connecting bones of the same left foot.
He immediately sensed he had evidence of the earliest hominid, or human ancestor, found in South Africa. Further research with Tobias revealed the apelike features of the bones and joints they formed, he said.
They said the find was further proof that humankind originated in Africa. Hominid fossils in Africa are older than those found anywhere else.