Ancient Greening of Earth Pushed Back to 2.2 Billion Years Ago

First Posted: Jul 23, 2013 07:42 AM EDT

Billions of years ago, our planet was barren and lifeless, containing an atmosphere that was far different than the one that is present today. In fact, scientists once believed that it was only about 500 million years ago that plants and life began to slowly emerge. Now, though, that date has been pushed back--far back. Researchers have discovered that the greening of Earth may have occurred as early as 2.2 billion years ago, which is almost halfway back to the inception of our planet.

Researchers discovered evidence of this ancient, primitive life in South Africa in the form of soil samples. These samples contained tiny fossils the size of match heads, connected into bunches by threads. Nicknamed Diskagma buttonii, these creatures were neither plants nor animals. Instead, they were probably some kind of fungi.

Actually examining these fossils was no easy task. They were too big to be completely seen in a standard microscopic slide and were found in rock that was too dark to see through in slabs. Instead, the samples were imaged using powerful X-rays of a cyclotron, a particle accelerator.

"They're certainly not plants or animals, but something rather more simple," said Gregory J. Retallack of the University of Oregon in a news release.

The species look like tiny urn-shaped structures with a small tube on the bottom of them. Although they're not sure exactly how this creature might have functioned or lived, the researchers have found that it has some similarities to three living organisms: a slime mold, called Leocarpus fragilis, a lichen, called Cladonia ecmocyna, and a fungus, called Geosiphon pyriformis. What is most interesting, though, is the fact that these creatures existed at a time far earlier than anyone expected.

"There is independent evidence for cyanobacteria, but not fungi, of the same geological age, and these new fossils set a new and earlier benchmark for the greening of the lank," said Retallack. "This gains added significance because fossil soils hosting the fossils have long been taken as evidence for a marked rise in the amount of oxygen in the atmosphere at about 2.4 billion to 2.2 billion years ago, widely called the Great Oxidation Event."

The new findings reveal a little bit more about the history of our planet. In addition, they show how these primitive creatures helped shape Earth's atmosphere which allowed other species to emerge.

The findings are published in the journal Precambrian Research.

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