A group of researchers led by Prof J. William Schopf from the University of California, Los Angeles, has discovered a type of deep-sea microorganism that appears not to have evolved over 2.3 billion years.
Modern and 2.3 – 1.8 billion years old sulfur-cycling microorganisms. Image credit: J. William Schopf et al.
Prof Schopf and his colleagues examined a mud-inhabiting sulfur-cycling microbial community that is 1.8 billion years old and was preserved in rocks from the Western Australian Duck Creek Formation.
Using innovative techniques, including confocal laser scanning microscopy and Raman spectroscopy, they found that the bacteria are essentially identical both to an older fossil community (2,300 million years old) from the same region and to modern microbial biotas discovered off the coast of South America in 2007.
“It seems astounding that life has not evolved for more than 2 billion years – nearly half the history of the Earth. Given that evolution is a fact, this lack of evolution needs to be explained,” said Prof Schopf, who is the first author on the study published in the Proceedings of the National Academy of Sciences.
The researchers said that the organisms’ lack of evolution actually supports Charles Darwin’s theory of evolution.
Prof Schopf explained: “the rule of biology is not to evolve unless the physical or biological environment changes, which is consistent with Darwin.”
“The environment in which these microorganisms live has remained essentially unchanged for 3 billion years.”
“These microorganisms are well-adapted to their simple, very stable physical and biological environment.”
“If they were in an environment that did not change but they nevertheless evolved, that would have shown that our understanding of Darwinian evolution was seriously flawed.”
He said: “the findings therefore provide further scientific proof for Darwin’s work.”
The fossils the scientists analyzed date back to a substantial rise in Earth’s oxygen levels known as the Great Oxidation Event, which scientists believe occurred between 2.2 billion and 2.4 billion years ago.
The event also produced a dramatic increase in sulfate and nitrate — the only nutrients the microorganisms would have needed to survive in their seawater mud environment — which the scientists say enabled the bacteria to thrive and multiply.
“The fossils are interpreted to document the impact of the mid-Precambrian increase of atmospheric oxygen, a world-changing event that altered the history of life,” the scientists wrote in the PNAS paper.
“Although the apparent 2-billion-year-long stasis of such sulfur-cycling ecosystems is consistent with the null hypothesis required of Darwinian evolution, additional evidence will be needed to establish this aspect of evolutionary theory.”
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J. William Schopf et al. Sulfur-cycling fossil bacteria from the 1.8-Ga Duck Creek Formation provide promising evidence of evolution’s null hypothesis. PNAS, published online February 02, 2015; doi: 10.1073/pnas.1419241112
