Ancient ape ruled out of man's ancestral line
Ancient remains, once thought to be a key link in the evolution of humankind, have
now been shown to be 400,000 years too young to be a part of humankind’s family
tree.
The remains of the apeman, dubbed Little Foot, were discovered in a cave
complex at Sterkfontein by a local South African team in 1997. Its bones
preserved in sediment layers, it is the most complete hominid fossil skeleton
ever found.
Little Foot is of the genus Australopithecus, thought by some to be part of
the ancestral line which led directly to man. But research by Dr Jo Walker and
Dr Bob Cliff of the University of Leeds School of Earth and Environment, with Dr
Alf Latham of Liverpool University's School of Archaeology, Classics and
Egyptology, shows the remains are more than a million years younger than earlier
estimates.
The team used uranium lead chronology to date the remains. Stalagmite layers contain traces of radioactive uranium,
which eventually decays to form lead. The team measured the amount of uranium
and lead in the stalagmite layers to form an accurate date for their age and for
that of the skeleton. Working on
extracts of stalagmite deposits from immediately above and below the body, they
dated the skeleton at around 2.2 million years old.
Uranium-lead analysis has proved to be more accurate than other dating
techniques as it does not rely on animal remains or sediment traces surrounding
the excavation site. Animal remains or sediment traces are often buried in many
layers of hardened deposits making it difficult for archaeologists to pin point
exactly where and when the specimens were in existence.
Dr Latham added: "Though these caves hold by far the most numerous
ape-man deposits in the world they have been very difficult to date accurately.
We have now opened up the way to dating more of these important fossils using
the uranium-lead technique."
Their findings, published in the American journal Science, are controversial.
Earlier estimates had put the age of Little Foot at three to four million years
old placing it potentially on a direct line to humans.
The first recognisable stone tools appeared in Africa around 2.6 million
years ago, but they were not made by Australopiths. Rather it is thought the
first tool maker was Homo habilis, whose evolution is believed to have led
directly to man. Rather than being older than Homo habilis – and a possible
direct ancestor – Little Foot is more likely a distant cousin.
His remains are cemented in hard mineral deposits in the Sterkfontein cave
complex which has yielded a number of other ancient finds. It is thought he
either fell down a shaft or somehow got trapped in the cave and died there to be
covered by the sediment layers from which he is now being slowly extracted.
These sediments are themselves sandwiched between stalagmite layers which
provided the materials for the dating process.
Australopithecus walked on two legs, but stood just 130cm tall and had a
brain comparable in size with a modern chimpanzee. As Dr Walker explained: “In
many of these finds, the smallest bones have disintegrated, but here the feet
and hands are well preserved - and these could enable researchers to show how
well adapted this early primate was to walking on two feet.”
But the sediment encasing Little Foot is harder than the bone – making
extracting him a painstaking process for the South African team.
And Drs Latham and Cliff have now turned their own attention to further
Australopith findings at Makapansgat, also in South Africa, where other
specimens of Australopithecus have been found. - Leeds.
More information:
 Contact: Simon Jenkins,
S.Jenkins@leeds.ac.uk
University of Leeds
Related articles:
Little foot; big footprint
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