The earliest known life in the geologic strata are colonies of filimentorus bacteria stromatolites 3.48 billion years old, and this article describes possible older fossils. The fossils depicted here are possible single celled tubular fossils found at mid-ocean sea vents, which would be more advanced single celled life forms than bacteria. ..
Earliest evidence of life on Earth 'found'
Earliest evidence of life on Earth 'found'
By Pallab GhoshScience correspondent, BBC News
Image copyrightM DODD
Image captionAncient life: These clumps of iron and filaments show similarities to modern microbes
Scientists have discovered what they say could be fossils of some of the earliest living organisms on Earth.
They are represented by tiny filaments, knobs and tubes in Canadian rocks dated to be up to 4.28 billion years old.
That is a time not long after the planet's formation and hundreds of millions of years before what is currently accepted as evidence for the most ancient life yet found on Earth.
The researchers report their investigation
in the journal Nature.
As with all such claims about ancient life, the study is contentious. But the team believes it can answer any doubts.
The scientists' putative microbes from Quebec are one-tenth the width of a human hair and contain significant quantities of haematite - a form of iron oxide or "rust".
Matthew Dodd, who analysed the structures at University College London, UK, claimed the discovery would shed new light on the origins of life.
"This discovery answers the biggest questions mankind has asked itself - which are: where do we come from and why we are here?
Image copyrightDOMINIC PAPINEAU
Image captionThis bright red "concretion" of iron-and silica-rich rock contains the features interpreted as microfossils
"It is very humbling to have the oldest known lifeforms in your hands and being able to look at them and analyse them," he told BBC News.
The fossil structures were encased in quartz layers in the so-called Nuvvuagittuq Supracrustal Belt (NSB).
The NSB is a chunk of ancient ocean floor. It contains some of the oldest volcanic and sedimentary rocks known to science.
The team looked at sections of rock that were likely laid down in a system of hydrothermal vents - fissures on the seabed from which heated, mineral-rich waters spew up from below.
Today, such vents are known to be important habitats for microbes. And Dr Dominic Papineau, also from UCL, who discovered the fossils in Quebec, thinks this kind of setting was very probably also the cradle for lifeforms between 3.77 and 4.28 billion years ago (the upper and lower age estimates for the NSB rocks).
He described how he felt when he realised the significance of the material on which he was working: "I thought to myself 'we've got it, we've got the oldest fossils on the planet'.
"It relates to our origins. For intelligent life to evolve to a level of consciousness, to a point where it traces back its history to understand its own origin - that's inspirational."
Image copyrightCREDIT: MATTHEW DODD
Image captionIron-rich tubes from the Quebec rocks provide additional evidence for life
Any claim for the earliest life on Earth attracts scepticism. That is understandable. It is often hard to prove that certain structures could not also have been produced by non-biological processes.
In addition, analysis is complicated because the rocks in question have often undergone alteration.
The NSB, for example, has been squeezed and heated through geological time
At present, perhaps the oldest acknowledged evidence of life on the planet is found in 3.48-billion-year-old rocks in Western Australia, which are bacteria stromatolites.
The simplist intermediates between self reproducing metabolic life and none life is bacteria and related simple organic forms. Most scientists consider bacteria not truly life, but the evolutionary intermediate between pre-life forms and living self reproducing life.