World's Oldest Fossils May Show Life on Earth 4 Billion Years Ago

Posted March 03, 2017

According to the University College London, the microfossils contain tiny filaments and tubes formed by bacteria that lived on iron. Dominic Papineau, the study's lead author, says these microorganisms can breathe and eat, and could be up to 4.28 billion years old. The chemicals and energy in these environments make them look like the flawless place for life to start.

However, not everyone is convinced: One scientist says there's no way to say for sure that these traces are evidence of life - or that they are truly ancient. The previous oldest found fossil was 3.7 billion years old, which is a huge difference. Collectively, these observations are consistent with an oxidized biomass and provide evidence for biological activity in submarine-hydrothermal environments more than 3,770 million years ago.

Before this find, the earliest accepted evidence for life were 3.7-billion-year-old stromatolite fossils from the Isua Greenstone Belt in south-west Greenland.

Dodd's team discovered these purported microbes in rocks believed to be up to 4.28 billion years old, which would have been several hundred million years earlier than the time during which the first now accepted evidence of ancient life on Earth would have existed, the BBC said.

In the study, Dodd and his colleagues identified a rocky outcropping of primitive ocean crust in Quebec, Canada, made up mostly of volcanic lava rock. They dated back 3.46 billion years, but some scientists had contested their biological origin. These deposits of gravel and sand accumulated about four billion years ago around iron-rich hydrothermal vents deep in the ocean, only to be uplifted by geologic processes over time until they emerged from the sea in northern Canada. That makes these the oldest known fossils and possibly the oldest known evidence for life on Earth. He had also found the presence of graphite, as well as the isotope carbon-12, which is a key ingredient in biological processes and life in itself. They appear in rock as red or white layers. The planet was eventually bombarded by comets, which scientists surmise is what brought the building blocks of life to Earth. Dodd examined hair-thin slices of rock from this formation and found intriguing features: tiny tubes composed of an iron oxide called hematite, as well as filaments of hematite that branch out and sometimes terminate into large knobs.

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The rock formations around the fossils hint that the microbes lived on the seafloor around hydrothermal vents or in the water near vents. The team also ruled out several alternative explanations, such as the wavy structures forming through rock stretching.

How old is life on Earth?

In a study published Wednesday by the journal Nature, scientists say the finding supports the idea that life may have begun near undersea vents where water was heated by a volcano.

An global team of researchers has managed to unearth the fossilised remains of a creature that lived 3,770 million years ago. As such, it's possible to argue that the signs of life may be more recent, even if the rocks themselves are ancient, he added. Since the fossils are almost as old as Earth, which formed some 4.5 billion years ago, the finding supports previous indications that life may have begun in such an environment, he said. One previously unknown mineral crystal, for instance, was found on a wooden pit prop deep in a nickel mine in Russian Federation.

Dr. Westwall also studies early microbes and has found that they tend to leave behind much smaller tubes, their growth constrained by the lack of oxygen on primordial Earth. That means these two vastly different lifeforms thrived on two totally different energy sources just 70 million years apart.