Oldest Evidence Of Life On Earth Claimed In 3.5-Billion-Year-Old Fossil

The Apex fossils in question. John Valley, UW–Madison

Researchers say they have discovered the oldest confirmed evidence of life on Earth, fossils inside a rock that dates back 3.5 billion years.

Published in the Proceedings of the National Academy of Sciences, the study describing the findings says that 11 microbial specimens from five separate taxa (organisms) were found.

"People are really interested in when life on Earth first emerged," John Valley from the University of Wisconsin, Madison, one of the study’s co-authors, said in a statement.

"I think a lot more microfossil analyses will be made on samples of Earth and possibly from other planetary bodies."

The study looked at microfossils that were actually collected back in 1982 in Western Australia, known as the Apex fossils, and later described in the journal Science in 1993. At the time, it wasn’t clear if these specimens were of biological origin, despite further supporting evidence in 2002. Others, however, had doubted the claims.

In this latest research, the team used a secondary ion mass spectrometer (SIMS) to separate the carbon composing each fossil from its constituent isotopes. They then measured the ratio of carbon-12 and carbon-13, and found it to be consistent with biological and metabolic function.

An example of one of the microfossils in the sample of rock. J. William Schopf, UCLA

“I think it’s settled,” Valley said, commenting on the question of the microfossils being biological, adding to IFLScience that this was now the oldest confirmed life on Earth.

While we can’t say much about what sort of organism would have formed this fossil, we can say it would have been the result of a diverse group of organisms. They would have relied on the Sun for energy, with some producing methane and others consuming it.

We think Earth may have had oceans as long as 4.3 billion years ago, and there doesn’t seem to be any reason life couldn’t have formed back then. Other research has hinted at life dating back 3.8 billion years or more.

This finding may have implications for life on other worlds, indicating that life can form even in trying conditions. Early Earth is thought to have been oxygen-free until about 800 million years ago, when photosynthetic life oxygenated the atmosphere, allowing complex life to form.

For now, life on Earth just got a little bit closer to its formation 4.5 billion years ago, suggesting it didn’t take long at all for our planet to become habitable.

"We have no direct evidence that life existed 4.3 billion years ago but there is no reason why it couldn't have," said Valley. "This is something we all would like to find out."


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