Fossils Point to Life on Earth 4 Billion Years Ago

oldest_fossil_earth_uclScientists have discovered remains of microorganisms in Canada that are between 3.8 and 4.3 billion years old, providing direct evidence of one of the oldest life forms on the Earth. Tiny filaments and tubes formed by bacteria that lived on iron were found encased in quartz layers in the Nuvvuagittuq Supracrustal Belt (NSB) in Quebec, Canada.


The NSB contains some of the oldest sedimentary rocks known on the Earth which likely formed part of an iron-rich deep-sea hydrothermal vent system that provided a habitat for Earths first life forms between 3,770 and 4,300 million years ago, researchers said.

“Our discovery supports the idea that life emerged from hot, seafloor vents shortly after planet Earth formed. This speedy appearance of life on Earth fits with other evidence of recently discovered 3,700 million year old sedimentary mounds that were shaped by microorganisms,” said Matthew Dodd from University College London (UCL) in the UK.

“These discoveries demonstrate life developed on Earth at a time when Mars and Earth had liquid water at their surfaces, posing exciting questions for extra-terrestrial life,” Dodd said.

Prior to this discovery, the oldest microfossils reported were found in Western Australia and dated at 3,460 million years old but some scientists think they might be non-biological artifacts in the rocks.

  • Systematically looked at the ways the tubes and filaments, made of haematite – a form of iron oxide or rust – could have been made through non-biological methods such as temperature and pressure changes in the rock during burial of the sediments, but found all of the possibilities unlikely.
  • The haematite structures have the same characteristic branching of iron-oxidising bacteria found near other hydrothermal vents today and were found alongside graphite and minerals like apatite and carbonate which are found in biological matter including bones and teeth and are frequently associated with fossils.
  • They also found that the mineralised fossils are associated with spheroidal structures that usually contain fossils in younger rocks, suggesting that the haematite most likely formed when bacteria that oxidised iron for energy were fossilised in the rock.

The fact that life kick-started not long after Earth formed suggests it could also emerge on watery worlds outside our Solar System at comparable stages of formation, the scientists said.

“If life happened so quickly on Earth, then could we expect it to be a simple process that could start on other planets?”, asked lead author Matthew Dodd, a graduate student at the London Centre for Nanotechnology.

The results were published in the peer-reviewed journal Nature.

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