Pigments found in 1.1bn-year-old rocks beneath the Sahara desert shed light on ‘major puzzle’ about early life
Scientists have discovered what they say are the world’s oldest colours – and they are bright pink.
The pigments were discovered after researchers crushed 1.1bn-year-old rocks found in a marine shale deposit, beneath the Sahara desert, in the Taoudeni basin in Mauritania, west Africa.
“Of course you might say that everything has some colour,” said the senior lead researcher, Associate Prof Jochen Brocks from the Australian National University. “What we’ve found is the oldest biological colour.”
Brocks compared it to finding a 100m-year-old T rex bone. “It would also have a colour, it would be grey, or brown, but it would tell you nothing about what kind of skin colour a T rex had,” he said.
“If you would now find preserved, fossilised skin of a T rex, so that skin still has the original colour of a T rex, say it’s blue or green, that would be amazing. That’s in principle what we’ve discovered … only 10 times older than the typical T rex.
“And the molecules we’ve found were not from a large creature but microscopic organisms because animals didn’t exist at that time. That’s the amazing thing.”
The colours were discovered by a Phd student, Nur Gueneli, who had crushed the rocks to a powder. She then extracted and analysed molecules of ancient organisms from the substance.
Gueneli said the pigments were more than half a billion years older than previous discoveries.
“The bright pink pigments are the molecular fossils of chlorophyll that were produced by ancient photosynthetic organisms inhabiting an ancient ocean that has long since vanished,” she said in a statement.
The research, supported by Geoscience Australia, was led by ANU and conducted with scientists from the US and Japan.
The rocks were sent to ANU from an oil company that was looking for oil underneath the rocks and sand of the Sahara desert about 10 years ago, Brocks said.
“They drilled a hole several hundreds metres deep and they hit a deep, black, oily shale,” he said. “It turned out to be 1.1bn years old, which is absolutely incredible.”
Brocks said when Gueneli, who is his student, had discovered the colours, he initially was in a state of disbelief.
“I remember I heard this screaming in the lab,” he said. “She came running into my office and said, ‘look at this,’ and she had this bright pink stuff.
“It turned out to be real pigment, 1.1bn years old.”
Brocks added that the discovery was “not just the coolness of having old, pink stuff”, but also helped to solve a “very major puzzle about life” – why large, complex creatures appeared so late in the Earth’s history.
While the Earth is about 4.6bn years old, Brocks said, animal-like creatures and other larger things like seaweed only emerged about 600m years ago.
When the researchers had analysed the structure of the pink molecule, they were able to find what had produced them – tiny cyanobacteria.
“They had been at the bottom of the food chain,” he said. “In the modern ocean we have algae at the bottom of the food chain. Microscopic algae are still very small but they are still 1,000 times bigger than cyanobacteria.
“And you need these larger particles as a food source for larger creatures to evolve. Looking at our molecules it became clear … there was no food source for larger creatures. It solves a very old question.”
Asked how he felt when he realised they had discovered the world’s oldest colours, Brocks said: “My first thought was just ‘wow’. I was just awestruck that these molecules can survive for such a long time.
“What I didn’t know was that these molecules could also solve a big scientific question.”