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Scientists find a new story to tell about the origins of life

March 5, 2017

Canadian fossils push back date of origins of life

Hudson Bay microbes proven to be up to 4.3bn years old

 	High quality global journalism requires investment. Please share this article with others using the link below, do not cut & paste the article. See our T&Cs and Copyright Policy for more detail. Email ftsales.support@ft.com to buy additional rights. 	https://www.ft.com/content/91d21da6-fe69-11e6-96f8-3700c5664d30 	Haematite filament enveloped by a fine, irregular layer of nanoscopic haematite from vent deposits. These filaments of iron, about half the size of a human hair, were made by primitive microbes involved in the carbon and iron cycles. Photo by M Dodd


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Haematite filament enveloped by a fine, irregular layer of nanoscopic haematite from vent deposits. These filaments of iron, about half the size of a human hair, were made by primitive microbes involved in the carbon and iron cycles. Photo by M Dodd

The world’s oldest known fossils have been found in ancient Canadian rocks, a discovery that will push back the accepted scientific timeframe for the origins of life on Earth.

Remains of microbes that lived 3.8bn-4.3bn years ago were identified in the Nuvvuagittuq belt in eastern Canada, some of the world’s oldest sedimentary rocks, by an international team led by University College London.

The microbes, which originated in a system of deep-sea hydrothermal vents, were formed by bacteria that obtained energy by oxidising iron minerals. Similar microbes live close to hot water vents in today’s oceans.

“Our discovery supports the idea that life emerged from hot seafloor vents shortly after planet Earth formed,” said Matthew Dodd of UCL, lead author of the scientific paper published in Nature magazine. Earth is understood to have formed about 4.5bn years ago.

Until now, the oldest individual organisms preserved as fossils were microfossils from Western Australia dated at 3.46bn years old.

Scientists also recently found mats of bacteria that lived in shallow water, known as stromatolites, in 3.7bn-year-old rocks from Greenland. “The Greenland stromatolites and our discovery show a rapid diversification of life in different environments,” said Mr Dodd.

Nick Lane, an evolutionary biochemist at UCL who was not involved in the research, said that the finds were “evidence of a vibrant early ecosystem” on Earth.

A high level of proof is required by scientists that ancient microfossils are really remains of living organisms rather than non-biological artefacts in the rocks. Several previous claims, notably the alleged discovery in 1996 of microbes in a Martian meteorite from Antarctica, were undermined by subsequent analysis.

This sparked the UCL-led team to undertake extensive chemical and physical examinations of the microscopic tubes and filaments found in the Canadian rocks to rule out other possible explanations such as temperature and pressure changes during and after the sediment’s burial and mineralisation.

They found that the microfossils, which are composed of the iron oxide mineral haematite, have the same branching structure as modern bacteria living near hydrothermal vents.

They are also associated with other carbon and calcium minerals that accompany fossils in younger rocks.

“The structures are composed of the minerals expected to form from putrefaction [of dead bacteria] and have been well documented throughout the geological record, from the beginning until today,” said Dominic Papineau, the project leader.

“The fact we unearthed them from one of the oldest known rock formations suggests we have found direct evidence of one of Earth’s oldest life forms.”

It is hoped that further research will narrow down the age range for the Nuvvuagittuq rocks.

The first geological era after Earth’s formation is known as the Hadean period, with intense volcanism, meteorite bombardment and a dense atmosphere rich in carbon dioxide. When Earth cooled enough for liquid water to form is not clear. But if life began quickly in Earth’s first oceans, the likelihood is increased of it being widespread elsewhere in the universe.

Because conditions on Earth and neighbouring Mars were very similar in the first few hundred million years of their existence, this raises hopes that fossils could be found in ancient Martian sedimentary rocks.

Mr Dodd said that unless Earth was a special exception, “we expect to find evidence for past life on Mars 4bn years ago”.

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