Oldest fossils on Earth? New look finds might be rocks

WASHINGTON (AP) – What were the oldest fossils on earth, according to a new study.

A couple of years ago, a team of Australian scientists found that they have been partially left over from microbes that lived on an ancient seafloor. They were said to be 3.7 billion years old, and they thought it would be better to think of Earth shaped.

But on Wednesday, the journal Nature, which published the 2016 study, released new research using NASA technology The Australian scientists, however, still maintain they are.

NASA Astrobiologist Abigail Allwood, who had found the former fossil at about 3.5 billion years old. When she reads the paper, she thought she was going to Greenland and looked herself.

Allwood found the shapes, the weathering and mostly the interior layers of the structures did not fit with this type of fossil, called stromatolites. One even was growing in what she called the wrong direction.

Then Allwood used a version of an instrument that is being sent to Mars in a few years to create a chemical map of the structure. She said it did not have the chemical signature of fossilized life.

Three outside experts told The Associated Press they agree with the newest research; none thought they were fossils as suggested by Allen Nutman at the University of Wollongong in Australia.

Many of these lines of evidence, "said scientists were impressed but not convinced by Nutman's work," said the University of Connecticut's Pieter Visscher. He said he was persuaded by Allwood's thorough work that it was not a fossil.

Nutman and his colleagues released a statement defending their work. They said Allwood took samples from the end of one of two sites and did not test the original specimens when offered.

"This is a clbadic comparing apples and oranges scenario, leading to the inevitable outcome that bears and their observations do not exactly match," they said in the statement.

Said another of the outside experts, Marie Catherine Sforna of the University of Liege in Belgium: "The search for traces of early life is difficult and controversial."

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Follow Seth Borenstein on Twitter: @borenbears

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The Associated Press Health & Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.