A recent study may have pushed the date back to 4.28 billion years ago
Scientists may have the date for the origin of life on Earth wrong by roughly 780 million years.
In school, we learned that life on Earth originated roughly 3.5 billion years ago, right? Apparently, that could be wrong. A recent study by Dominic Papineau of University College London may push the date back to 4.28 billion years ago. This suggests that the first microorganisms popped up on our planet only 300 million years after it formed. That is about the time the Sun takes to complete a spin of our galaxy.
If Papineau did break new ground, he has gremlins to thank for it.
“I went to McGill University where I knew already when I started that I wanted to study something that would relate to extraterrestrial life,” Papineau told Truly Curious. “I had already been bitten by that bug.”
Sci-fi movies aroused Papineau’s interest in extraterrestrial life from an early age.
“I then realized that all of this is fiction, of course,” he said. He got over the disappointment that gremlins, Yoda, and ET were not real.
“There is an actual scientific question that drives everything I do now,” Papineau assures us. He is now an associate professor of geochemistry and astrobiology at UCL. A PhD from the University of Colorado at Boulder, he is also on the board of the Center for Planetary Sciences at UCL.
While this study of planetary life may not cross space as much as it does time, even with all the preparation fiction had given him, Papineau – and his team – could still be surprised by some very odd data.
The team was analyzing an ancient sedimentary rock dating back to anywhere between 3.75 and 4.28 billion years ago. Earlier, as described in a 2017 paper, they had found some filaments, knobs, and tubes. By cutting the rock into thin layers, the team came upon an incredibly large and complex tree-like structure.
Life may find a way – fast
According to Papineau, given its complexity, such a formation can only be the result of microbial activity. But once they dated it, the team concluded that life may have started on Earth earlier than previously thought.
As mentioned, the team has analyzed the rock, collected in 2008, several times over. They had seen filaments, tubes, and irregular spheroids, but the rich network they found recently stood out from the other elements, thanks to its complexity and size.
“There is this overarching structure which is about one centimeter in size,” Papineau explained. “We are talking about a life form visible to the naked eye. This tree-like formation, called pectinate-branching, has a main stem, from which different filaments branch out on one side. When we think about the origins of life, we think about very tiny little microbes. That’s what we would expect – complexity to increase over time, not to start large and complex. That’s not what we saw.”
They had missed this tree-like formation earlier. Papineau pointed out that scientists tend to cut slabs of 30 nanometers, but that was too thin for them to observe bigger structures like this one.
In their last analysis, Papineau had opted for samples measuring from 60 to 100 microns, about the thickness of a piece of paper. That’s when this structure suddenly popped up. The team analyzed the rock through detailed microscopy. They took several pictures that they pulled into a supercomputer, where they came together in a 3D video that revealed the details – filaments, spheroids, and the big tree-like network.
These structures are not new to scientists and can be observed even nowadays in several locations in the world. For instance, in the underwater volcano Loihi in Hawaii as well as in the Indian and Arctic Oceans. According to Papineau and his team, these are the result of microbial activity and derive from bacteria causing the rusting of iron.
“The filaments themselves are thought of being the byproduct of the excrement of these microorganisms,” he said. The paper also suggests that the tree-like structure they found was created by a community of organisms rather than a single one.
A rustful time
Iron oxidation is known to occur next to hydrothermal vents, cracks in the oceanic floor from which hot water gets expelled after being heated by the underlying magma.
It is perhaps not by chance that the rock sampled by Papineau and his team used to be located next to hydrothermal vents.
The sample came from Quebec’s Nuvvuagittuq Supracrustal Belt, where some of the oldest rock formations on Earth can be found. Scientists believe that billions of years ago, these rocks were part of the oceanic floor and were located next to hydrothermal vents. Many of them believe that life first originated in such settings.
“There have been various hypotheses for the origins of life, but one that’s been sticking around ever since we know about hydrothermal vents is that these environments provide very strong chemical gradients,” Papineau said. “You have some seawater that goes through cracks in the ground, gets heated and dissolves different minerals… The fluids that come out are very different from seawater. That creates gradients [of minerals], opportunities for microbes to take some of these things and transform them. That’s one of the main reasons why people think life originated in the hydrothermal vents.”
A time for healthy doubt
Despite his evidence, some people in the scientific community remain skeptical about the research.
Some believe the structures Papineau and his team found are the results of later infiltration by microbes. Others claim that the rock just isn’t as old as stated in the paper.
Papineau concedes that the first assertion could be true.
“People have rejected our interpretation on the basis that our rocks have not been mapped in high resolution in the field,” he said. “I confess this is true. I did not have the time to do the required detailed geologic map when I was there, and because of the pandemic we haven’t been able to return.”
But he brooks no criticism about his measurement about how old the rock is.
“I’m very comfortable with the age of the rock. It has a minimum age of 3.75 or 3.77 [billion years]. It depends where you take that cut-off, but that’s approximately the minimum age. And then the possible age of the rock is 4.28 billion years.”
Papineau dismissed suggestions from some others that the different structures found in the rocks could be the result of metamorphism – the alteration of the structure of a rock due to heat, pressure, and other natural processes occurring over billions of years. He pointed out that their sample is full of microfossils, which are hard to find in rocks that undergo such processes.
Despite the need for more analyses, there is some evidence that life on Earth originated well before what we had thought. Such findings have huge consequences for the whole scientific community.
“This has biological implications because it pushes back the clock for the origins of life, for the rise of complex life, iron-oxidizing bacteria, sulfur metabolisms, and large, complex, and diverse microbial communities,” Papineau said.
Given that he is an astrobiologist, Papineau considers another possibility: if life began this early on Earth, why could it not do elsewhere, too?
“I think that if we can make a solid case as we did on Earth – and still not everybody will agree with us, I know that,” he said. “the bar is very, very high on the biosignatures [a scientific word referring to signs of life] of Mars and a lot of other planets, too.”
No wonder the Mars Perseverance Rover used the same technology as the Papineau team did to look for biosignatures on our neighboring planet.
While it’s still too early to affirm anything with certainty, the current research suggests that, with the possibility of life emerging in such inhospitable settings, Papineau’s dream of finding extraterrestrial life may have received a boost.
Cristina Miceli is a freelance writer with a master’s degree in journalism from the University of Limerick
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