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When Did Life Begin On Earth?

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It is the question often asked: When did life begin on Earth? Perhaps more than 3.7 billion years ago, according to scientists who discovered unusual rocks in Greenland. This is even earlier than previously thought.

In a study published this week in the journal Nature, a team of Australian researchers described the small cone-shaped structures they found. These may have been built by microorganisms shortly after the planet was born.

The work adds to the evidence that life has flourished on Earth since its infancy.

"If these really are the figurative tombstones of our earliest ancestors, the implications are staggering," geologist Abigail Allwood wrote. She is a scientist who studies rocks.

Researchers Make A Surprising Discovery

The search for the earliest signs of life on Earth has taken many different
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They would expect to find them in areas where the rocks were half a billion years younger, Allwood wrote.

Rocks Reveal Clues

But these rocks are some of the oldest on the planet. Because they are so old, the research team will have to work hard to convince other scientists that the structures really are evidence of early life.

The rocks do not contain any biological remains. However, the authors point to four clues that suggest the small mounds were built by ancient life forms.

These include the cone shape of the structures, along with their layered internal structure. Another clue is the appearance of the sedimentary layers between the cones. These seem to have formed as sediment piled up against the cones as they stuck out of the sea floor.

The mineral content of the stromatolites is also different from that of the surrounding rocks.

More To Seek Out

The evidence is not perfect, Allwood said. While she believes the structures were made by ancient life forms, Allwood admits that she cannot rule out other possibilities. For example, they could have formed through mineral precipitation from
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