Josh Milton
Published November 22, 2025 9:45pm
Updated November 22, 2025 9:45pm
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The Earth had slightly less concrete, plastic and rubbish than it does now back in the day (Picture;
Humans, as goofy and dumb as we can be at times, are actually seriously complicated creatures.
We’re made from organs, bones and a strange, wrinkly body part called the brain that may or may not be the reason we’re conscious beings.
But a few billion years ago, life leaned more on the simpler side of things – think single-minded cells and rather literally-named microbial mats.
And these critters may have been wriggling around Earth a billion years earlier than we thought, according to a study published Monday.
The Archean eon, about four billion years ago, when the first life on Earth began to form (Picture: SwRI/Dan Durda, Simone Marchi)
Researchers have discovered chemical traces of life in rocks older than 3.33 billion years.
The traces of carbon were found inside a deep layer of rock in Mpumalanga, a small province in the east of South Africa.
Whatever life made these ‘whispers’ were not much younger than the Earth, which formed 4.5 billion years ago, suggesting that it didn’t take long for the planet to become habitable.
‘Three billion years ago, the Earth was very different,’ Solomon Hirsch, an astrobiologist at Imperial College London, who was not involved in the study, tells Metro.
‘The globe was almost entirely covered by ocean, with the very first continents just starting to form.
‘Life was much simpler than it is today, in the form of single-celled microbes that survived in places like hydrothermal vents where they harnessed energy from the chemical reactions that take place there.’
A an almost billion year old seaweed fossil from Yukon Territory, Canada (Picture: Katie Maloney)
Finding any traces of this life is next to pointless, however, given that the Earth has buried, crushed or heated most evidence of it over the years.
So a team of researchers, led by the Carnegie Institution for Science in the US, thought outside of the box.
Instead of looking for fragile fossilised cells or squishy biomolecules, they hunted for the chemical fingerprints that only organisms can leave behind.
To do this, the scientists used AI to examine 406 samples of everything from fungi to meteorites for blink-and-you’ll-miss-it chemical traces.
Among them was a well-preserved one-billion-year-old seaweed fossil from Yukon, Canada, so tiny it can only be viewed through a microscope.
The algorithm managed to detect traces of life in the Josefsdal Chert, a layer of 3.33 billion-year-old rock torn apart by Earth’s primordial crust.
These black smears may not look like much, but its traces of photosynthesis dating back 2.5 billion years (Picture: Andrea Corpolongo/Carnegie Institution for Science)
This layer of rock is hundreds of millions of years shy of the signs of life in Earth’s oldest fossils.
It’s not to say that some of the even older samples the algorithm examined, as ancient as nearly four billion years ago, weren’t biological.
The samples may be simply so damaged that the chemical traces are no longer discernable, even to AI.
The team also discovered lifeforms doing something quite groundbreaking (by primitive Earth standards, at least) at least 2.5 billion years ago; oxygen-producing photosynthesis.
Before the study, the biomolecular signature of the earliest photosynthetic lifeforms were found 800 million years after that.
Hirsch says that this method could be used to pick up on biosignatures – things only life can leave behind – in rock too faint for humans to see.
Organic material found in 2.5-billion-year-old sedimentary rock (Picture: Andrea Corpolongo/Carnegie Institution for Science)
‘This could be especially useful to apply to some of the oldest fossils on Earth which have had been degraded over billions of years, making it much harder to tell if they are really signs of ancient life,’ she adds.
For Hirsch, however, this method isn’t just for examining dusty old microfossils – it’s for searching for alien life, too.
‘The technique could also potentially be used to identify signs of life beyond Earth in places like Mars where any remains of past life there may have been fossilised,’ she says.
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Previous Page Next PageUsing this method to see if the truth is out there would involve doing something risky, however – trust AI.
‘Computers don’t have a way to explain to us why it thinks a sample may be biological or not,’ Hirsch says.
‘This could be a difficult for the search for alien life, where the burden of evidence is so high, and the chemistry of life could be completely different to what we know on Earth.’
Get in touch with our news team by emailing us at [email protected].
For more stories like this, check our news page.
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