Frankly, I don't know what more balanced mix of human and chimp features could be demanded of a "missing link".
Posted on 04/25/2003 12:12:50 AM PDT by Pro-Bush
Scientists taking a fresh look at a celebrated find of apeman remains in South Africa say they are convinced it is around four million years old, a discovery that will reshape our knowledge about the possible forerunners of human beings.
The researchers have applied new dating techniques to "Little Foot," a remarkably intact Australopithecus skeleton which is the star of the Sterkfontein caves - a treasure trove of fossils about 50 kilometre north-west of Johannesburg.
A two-footed creature with ape-like facial features, Australopithecus was a species of hominid that lived several million years ago and may have been the ancestor of our own genus, Homo, which appeared on the scene around 2.3 million years ago and later evolved into modern man, Homo sapiens.
Australopithecus remains have been found in eastern and southern Africa, but where the species originated and how it spread have never been determined.
Until now, the sketchy evidence suggested the enigmatic creature first arose in modern-day Kenya and then spread to southern Africa, something that indirectly bolstered the east's money-spinning claims to be the "Cradle of Humanity."
Little Foot, found in 1997, was initially dated by its discoverers to be 3.3 million years old.
That technique was based on so-called magnetic reversal: matching the magnetic field of mineral deposits in the rocks in which the fossil is imbedded with known switches in the Earth's magnetic field.
Every so often, the planet's magnetic field goes through a 180-degree switch, and this switch is reflected in the mineral layer.
When the field flicks back, so does the field in the subsequent rock layers.
But the problem, though, is that this age estimate is rough, and there is the risk of error if reversals are missed or mismatched.
Writing in Friday's issue of the US journal Science, the same team report that they have employed a new dating technique, based on the decay of radioisotopes in the rocks through cosmic rays - energy particles from space that bombard the Earth.
The new estimate puts Little Foot at a mighty 4.17 million years old, making it not just the most ancient hominid discovered in South Africa but a contemporary of the Kenyan specimens which were previously believed to be the earliest species of Australopithecus.
"The newly-dated Sterkfontein fossils may well be contenders for a place in the lineage from which humankind arose," the South African members of the team declared in a press release.
"What they tell us is that the genus Australopithecus was widely dispersed across the African continent for a period of at least two million years. During that time, several different species of Australopithecus evolved."
Despite Little Foot's astonishing age, it is still not the earliest hominid found.
That honour is disputed by fossils aged six to seven million years old that have been found in Kenya, Chad and Ethiopia, although all of this evidence is fragmented and their links to our genus are cloudy.
The study is written by Tim Partridge and Ron Clarke of the University of Witwatersrand in South Africa and Darryl Granger and Marc Caffee of Purdue University in the United States.
Frankly, I don't know what more balanced mix of human and chimp features could be demanded of a "missing link".
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