Scientists find 'earliest evidence of life on Earth'

Leslie Dixon
March 4, 2017

The ease of starting life on Earth implies we should find aliens living elsewhere.

While there is some debate as to whether or not the the age of the rock in the Nuvvuagittuq Greenstone Belt is 3.8 billion years old or 4.3 billion years old, Jonathan O'Neill, assistant professor at the University of Ottawa's Department of Earth and Environmental Sciences, believes it to be on the older side.

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. Other scientists are skeptical about the new claims.

"The morphology of these argued iron-oxidising filaments from Northern Canada is not convincing", she told BBC News. But what he found was surprisingly robust evidence that life here was already fairly evolved.

Planet Earth itself is believed to be 4.5 billion years old. And these rocks tend to be twisted up and chemically altered by heat and pressure, making it devilishly hard to detect unequivocal signs of life. The study was partially funded by NASA. "There's only so much you can do with them".

Today, such vents are known to be important habitats for microbes.

Now, researchers writing in the journal Nature say they found fossils of what could be some of the earliest known creatures to grace the Earth, embedded in rocks that are at least 3.7 billion years old. Hydrothermal vents deep beneath the oceans have always been thought to be where life originated, leading Matthew Dodd and colleagues to search where they did. The Earth started cooling down after that impact, with the magma-covered surface hardening into the planet's first crust. As the water cools, the metals settle out, forming towering spires and chimneys. Such hardy communities, scientists have suggested, may not only have thrived on early Earth, but may also be an analog for life on other planets.

"This makes life appear to be a relatively easy process to kickstart on the planet", says Matthew Dodd, a Ph.D. student at the University College London.

Earth is thought to be about 4.57 billion years old.

These tubes were encased in quartz layers in the Nuvvuagittuq Supracrustal Belt, Quebec, Canada.

The experts studied tubes and filaments preserved in the rocks that resemble similar structures attributed to bacterial life seen in other seafloor hydrothermal environments. Papineau was initially skeptical.

"Within the last 15, 20 years, we have more and more evidence that that's not the case", he said. We found these in the form of isotopically light carbon in graphite, associated with carbonate and apatite in and around the microfossils. However, lead researcher Matthew Dodd is confident that his team's Canadian discovery will hold up to the scrutiny. This research gets the oldest life on Earth by these bacteria.

That doesn't necessarily mean that life originated in deep waters rather than in shallow seas, Papineau says.

"We are talking about very, very simple shapes here".

Some, Dodd says, look like "strings of iron".

But researchers like Konhauser remain skeptical of the paper's conclusion.

"The tubes and filaments are best explained as remains of iron-metabolizing filamentous bacteria", they wrote, "and therefore represent the oldest life forms recognized on Earth". Moreover, he notes, if the tubes were formed by iron-oxidizing bacteria, they would need oxygen, in short supply at this early moment in Earth's history.

The oldest microfossils previously reported were found in Western Australia and dated to 3.46 billion years ago, though some scientists say that these are not biological in origin.

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