Little Foot, the first complete fossil Australopithecus skeleton, found at Sterkfontein nine years ago, has raised questions about whether the cave complex near Krugersdorp really is the ”Cradle of Humankind”.
Ron Clarke, celebrated palaeo-anthropologist and Little Foot’s ”caretaker”, insisted that Africa, not South Africa, had to be seen as the cradle. He suggested that fossil hominids such as Kenyanthropus, discovered in Kenya in 2000, were more likely to be our direct ancestor than Australopithecus. However, questions still remained about whether Kenyanthropus was a genus in its own right.
Clarke was speaking ahead of a keynote address on the latest developments in evolutionary research, and specifically Little Foot, to the Standard Bank Palaeontological Scientific Trust on October 24 entitled ”Out of the Lime Quarry into the Limelight: the Renaissance of Little Foot”.
Clarke said human evolution remained an unfinished puzzle, but he and other anthropologists across the world were slowly finding the missing pieces. ”We have to be open-minded and optimistic that we’ll find those pieces.”
He has been meticulously unearthing the Little Foot skeleton since he, Stephen Motsumi and Nkwane Molefe discovered it in 1997. He plans to remove the skull in the next few months, but says the going is extremely slow.
”We can’t use chisels, because the skull is set in a natural concrete,” he says. ”We are using specialised tools that will ensure the bones don’t get damaged.”
The anthropologist uncovered the lower legs of the 3,3-million-year-old hominid after a Sherlock Holmes-like investigation, when he noticed in a basement small bones uncovered by lime miners in the 1920s.
They led not only to the only complete adult Australopithecus skeleton yet found, but also to the only complete Australopithecus skull, hand, arm and leg.
”Each bone reveals a wealth of information about human ancestry, and gives important clues about our past,” Clarke says.
He believes, for example, that the skeleton shows that humans did not descend from knuckle-walking apes, but walked upright from the outset. Evidence for this lies in its hand, with a short palm and long and well-developed thumb compared with its fingers.
”It is the same as the modern human hand, but different from the apes, with their relatively much shorter thumbs, longer palms and longer curved fingers,” he says. ”Apes had a specialised hand to help them move around in the trees. They also have longer arms.”
He said it was extremely unlikely that the apes’ specialised hand had reverted to the australopithecine extremity.
Clarke’s conclusions also raise questions about whether Australopithecus was ancestral to modern humans. Although scientists initially believed human evolution followed a direct line, the many hominid discoveries over the past century have indicated that several different types of ape-men lived at the same time.
”Basically two theories have been held for the past few years,” Clarke said. ”The most popular theory was that the human genus, homo, evolved from Australopithecus.” The other, propagated by Kenyan anthropologist Lewis Leakey, holds that Australopithecus is an evolutionary offshoot.
New discoveries and arguments had given weight to Leakey’s hypothesis that homo and Australopithecus evolved separately, he explained.
Clarke said that if homo and Australopithecus co-existed it was highly unlikely that they belonged to the same genetic lineage.
Alhough Sterkfontein was being marketed as the Cradle of Humankind, ”those of us who work with bones” believe that the whole of Africa had to be seen as humankind’s place of origin.
But he added with a smile: ”It’s not impossible that Asia could still lay claim to the term. Who knows?”
Three years ago, Clarke and Tim Partridge of Wits University, and Darryl Granger and Marc Caffee of Purdue University in the United States dated Little Foot as being 4,17-million years old using the revolutionary ”cosmogenic burial technique” for dating fossils, which calculates their age based on the known decay rate of unstable radioactive isotopes.
This was considerably older than the estimate of 3,3-million years Clarke and Partridge reported in 1999, when they first dated the skeleton.
”We were surprised and a little dubious about the new dating, but accepted it because the lab results showed it to be sound,” Clarke says. ”Subsequently, United States physicists have raised doubts, and we’ve gone back to the 3,3-million-year figure.”
Clarke says the hard work in teasing out the evolutionary implications of Little Foot will only start once the skeleton is completely removed from its resting place.
”Then we will be able to compare it with other samples of Australo-pithecus, although some comparisons are already possible,” he says.