The excavation site for Little Foot's skull in the flowstone of Sterkfontein Cave, South Africa. New research puts the fossil's age as much younger than previously thought.
Credit: Science
PARIS: A fossil of an ancient human relation found at South Africa's Sterkfontein Cave is far younger than initially thought, according to a new study.
'Little Foot,' a fossil with both ape-like and human features, was found in the cave, a treasure trove of human relics, in the 1990s.
It was first dated to between 3.0 and 3.5 million years old, and later to more than 4.1 million years.
The ancient dates generated excitement, as they threw up a South African contemporary to 'Lucy', the famous Australopithecus afarensis fossil found in Ethiopia's Awash Valley in 1974 and, until Little Foot's discovery, chief contender for the title of ancestor of mankind.
But a paper published in the U.S. journal Science on Thursday said Little Foot's age is likely to be much younger - around 2.2 million years.
If so, rather than being man's direct ancestor, Little Foot is more likely to have been a distant cousin.
The dating method is based on a measurement of an isotope of lead, Pb 206, derived from the decay of uranium 238, on layers of rock above and below the fossil. As the rock ages, more U-238 decays in to lead. By measuring the ratio of lead to uranium, scientists can pinpoint the age of the rock.
Sterkfontein, located 50 kilometres north of Johannesburg, has produced about a third of the world's known early hominid fossils.
Little Foot was discovered by South African palaeoanthropologist Ronald Clarke.
In 1994, Clarke spotted four left-foot hominid bones as he sifted through bags of fossilised animal bones that had been dumped after a mine blast, decades earlier, at a large cavern within the cave system.
He attributed them to the hominid genus Australopithecus, and, because the bones were relatively small, the specimen was dubbed Little Foot.
Clarke spent the next few years exhaustively going through other bags of the fossils, and eventually found further foot bones from the same individual.
That prompted a search for further remains in the grotto which, even more remarkably, yielded the bones' owner - a nearly complete skeleton, cemented in a tough sedimentary rock called breccia, which has been gently excavated ever since.
Debate has always swirled around the dating of Little Foot, with paleontologists jousting over the age of sedimentary layers, the remains of fauna found within them and residual magnetic polarity found in ancient rock.
Fixing a date is important ascertaining when our ancestors began to use tools.
The first recognisable stone implements appeared in Africa around 2.6 million years ago, and the toolmaker is believed to be Homo habilis, whose evolution - apparently from a species of Australopithecus - is considered by some to have led directly to man.
Bob Cliff, an expert with the School of Earth and Environment at the University of Leeds, England, said that the earlier dating of Little Foot itself posed a conundrum.
It raised questions as to this genus' place in the hominid tree, if smarter hominids had split from Australopithecus many hundreds of thousands of years before.
Cliff acknowledged that the dating issue would remain a matter of heated debate, as paleontological pride and prestige were involved. "It's going to be controversial," he said.
Early human ancestry
I would not take any single fossil as a representative of an ancestor species, but as whole, there is nothing to point against early hominids not branching out of or to the homo branch, and nothing against the survival of other populations of hominids. Just like homo erectus/ergaster branched out to several different populations that seem to have been all displaced by archaic homo sapiens, which I would classify as the descendants of the african homo erectus, the survival of a sister species is not that uncommon. What I really find intriguing, is why Australopithecines went extinct.
It is easy to come up with explanations for the later displacement of earlier homo species/populations like the Neanderthals and Asian homo erectus, as they're documented rather well in the archeological record. I don't like much of some people's insistence that australopithecines weren't direct ancestors, as they were clearly predecessors of the genus homo. The survival of australopithecines for longer than previously known only supports that idea of descent from those forms; a lesser timespan would indicate that they were not well so adapted.
We have only one living example of that tree. The extinction of the Neandertals obviously had to do with the arrival of homo sapiens in Europe. They were gone from the middle-east first, and their extinction geographically follows a clear pattern: the arrival of our species. How does this relate to australopithecus? Homo erectus specimens have been found dated 400000 years after 2.2 million years B.P. I'll find it unlikely to find any surviving populations of australopithecines after that 2 million year mark, but if they're found, we don't have to write anything anew, and it's not such a big deal. It's how evolution works. Interesting times.
Homo habilis
The stone tools found have been associated with homo habilis remains, but I don't think there's any need to think that any australopithecines used specifically made stone tools, unless there is clear evidence of such activity, as cores and flakes.
We can push back the time when our ancestors started using manufactured tools, but I don't think this find is any proof of that. Chimpanzees today use tools, but not manufactured tools. They do not flake their stones they use as hammers. Austropithecines were certainly more humanlike than than any other primate living today, but they didn't use manufactured tools.
A chimpanzee or an orangutang can use implements from their surroundings to break a nut or, in the case of chimpanzees, kill a monkey when they hunt together for them. They don't make tools, they use what ever they've got handy. I think that particular tool-making thing evolved back 2 to 3 million years ago, by all evidence. If you can prove that before homo habilis there was a "handy man", go for it and present the new evidence.
There was a bush of creatures, almost like us, but not us, going back millions of years. I don't find it productive to consider them humans, as they thought differently, and they were less inclined to do what we do now for granted. Their lives were short and brutish, but not less emotional. Why do we exist today is because they survived, loved and cared for their children.
Could Little Foot Be a Remnant of a Population Ancestral to Us?
It's not impossible for a remnant population to exist long after the main population has disappeared. Little Foot could be such a remnant of a much earlier population. Being transitional between ape and man, these beings certainly could be descendants of the same beings that we descended from, even though they lived at the same time as more evolved hominids.
I remember reading of Homo erectus remains only 25,000 years old found in Java. This would be some 500,000 years after a flourishing Homo erectus population was living in Asia and had presumably long since disappeared. 25,000 years ago was contemporary with Homo sapiens in Europe, the cave artists.
I speak as a cultural anthropologist who is interested in paleoanthropology.
Arnold Perey, http://www.perey-anthropology.net