August 22, 2011
World’s Oldest Fossil Reportedly Discovered In Australia
Researchers from the University of Western Australia and the University of Oxford have unearthed what they believe are the oldest fossils ever discovered-single-celled organisms that are thought to be 3.4 billion years old, according to a Sunday article by Nicholas Wade of the New York Times.
The discovery, which is detailed in the latest edition of the journal Nature Geoscience, took place in a remote location known as Strelley Pool, which is located in Western Australia. The team that located the microfossils, which were located in sandstone at the base of a rock formation there, was led by David Wacey of the University of Western Australia and Martin D. Brasier of the University of Oxford.
"At last we have good solid evidence for life over 3.4 billion years ago," Brasier, a member of the university's Department of Earth Sciences, said in a statement Monday. "It confirms there were bacteria at this time, living without oxygen."
According to a press release posted to the Oxford University website on Monday, at the time the fossilized organisms would have been alive, the planet would have been "a hot, violent place“¦ with volcanic activity dominating the early Earth." While the sun would have been far weaker than it is in modern timed, cloud cover would have helped seal in the warmth, causing oceans to reach approximately "the temperature of a hot bath."
"It was in these conditions, the geologists believe, that organisms resembling today´s bacteria lived in the crevices between the pebbles on the beach," Wade reported in his article. "Examining thin slices of rock under the microscope, they have found structures that look like living cells, some in clusters that seem to show cell division."
While, as Wade points out, "cell-like structures in ancient rocks can be deceiving--many have turned out to be artifacts formed by nonbiological processes," Braiser told the New York Times that they have used advanced techniques to analyze miniscule areas within those structures and had discovered "carbon, sulfur, nitrogen and phosphorus, all within the cell walls."
"The microfossils satisfy three crucial tests that the forms seen in the rocks are biological and have not occurred through some mineralization process," Oxford University said in its media advisory. "The fossils are very clearly preserved showing precise cell-like structures all of a similar size. They look like well known but much newer microfossils from 2 billion years ago, and are not odd or strained in shape."
"The fossils suggest biological-like behavior. The cells are clustered in groups, are only present in appropriate habitats and are found attached to sand grains," the school added. "And crucially, they show biological metabolisms. The chemical make-up of the tiny fossilized structures is right, and crystals of pyrite (fool's gold) associated with the microfossils are very likely to be by-products of the sulphur metabolism of these ancient cells and bacteria."
Wade notes that UCLA Paleobiologist J. W. Schopf unofficially holds the record for discovering the oldest microfossil on Earth. In 1993, Schopf discovered what he believed to be fossils 3.465 billion years old in Western Australia. While those fossils would be roughly 65 million years older than the ones discovered by Brasier and his colleagues, the New York Times says that the Oxford researcher has challenged the validity of Schopf's find, claiming that they are not biological in nature, but rather minerals.
In addition to the interesting nature of the discovery itself, the fact that it is believed to have come from a oxygen-free environment has led some to wonder whether or not it could potentially prove that life could exist on the planet Mars. That theory was the subject of a Sunday article by Kate Kelland of Reuters, who discussed the possibility with Braiser.
"Could these sorts of things exist on Mars? It's just about conceivable. This evidence is certainly encouraging and lack of oxygen on Mars is not a problem," he told Kelland, who asserts that Braiser's team's find "suggests early life was sulphur-based--living off and metabolizing sulphur rather than oxygen for energy."
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