New fossils show life on Earth at least 3.7bn years old

by Edgar Hayes September 2, 2016, 0:49
New fossils show life on Earth at least 3.7bn years old

Rocks recently exposed after a once-permanent layer of snow melted were found to contain stromatolites, sediments the researchers said had been created by the growth of layer upon layer of micro-organisms. The fossils were discovered by a team of geologists and paleontologists led by Allen Nutman at the University of Wollongong in Australia.

The analysis placed the stromatolites between 3.71 and 3.695 billion years of age.

"The 3,700 [million-year-old] life already had a considerable prehistory, and supports model organism chronology that life arose during the Hadean [era]", the paper said. "We can now say that life populated shallow water settings, but we have no idea of how diverse other habitats were".

She said the discovery could have significant implications for the search for extraterrestrial life. That's also how the scientists ascertained the date for formation. The previous record-holder, the well-known 3.5-billion-year-old stromatolites of Western Australia, has now been unseated by a wide temporal margin.

Given the nature of the discovery, there will be much discussion and debate before the authors' claims that they have found the world's oldest evidence of biological life are widely accepted by the scientific community, the Times noted. And the structures that Nutman, Bennett, and Friend discovered in Greenland are 3.7 billion years old-220 million years older than the Australian ones.

Scientists still aren't exactly sure how life kickstarted itself on our planet all those billions of years ago. Charles Darwin hypothesised that life emerged in a "warm little pond", but other researchers imagine that it emerged around a deep-sea hydrothermal vent, or even came to Earth from space, perhaps after sparking into existence on Mars, or even in some other, distant planetary system. Moreover, very old rocks - older than 3 billion years - are exceedingly rare, because the Earth's surface has been eroded over time and recycled through plate tectonics. Paris Institute of Earth Physics researcher Pascal Philippot, who has worked on those oldest Australian stromatolites, told Ars that having only a few specimens to look at makes this tricky. "The evidence is a whole lot thinner than the rocks in Australia", says Abigail Allwood, an astrobiologist at NASA's Jet Propulsion Laboratory in Pasadena, California.

"These examples underscore the problem that we really have not yet found sufficiently well-preserved very old - ie, between 3500 and 4000 million (3.5 and 4bn) year - sediments to be confident that what we are seeing could definitely be regarded as stromatolites", he said. She said the evidence wasn't conclusive enough that it was life and not a geologic quirk.

Australian and United Kingdom scientists have dug up the oldest fossils found on Earth to date - 3,700-million-year-old sedimentary formations created by clumps of bacteria - which predate the current earliest fossils by a whopping 220 million years, and suggest life originated here more than 4,000 million years ago. Nutman and his colleagues outlined their fossil discoveries today in the journal Nature. "It would be like going to somewhere on Earth now and picking up some shells from a beach and getting the impression, "Oh, that's the full diversity of life that is on the planet". "If life could find a foothold here, and leave such an imprint that vestiges exist even though only a minuscule sliver of [rock] is all that remains from that time, then life is not a fussy, reluctant and unlikely thing", Allwood writes.

The Red Planet is believed to have once run with water and had an atmosphere, which together with warmth, could provide the right conditions for bacterial life. "Three thousand seven hundred million years ago, Mars was wet".

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