Scientists from Australia, Japan and the US have uncovered what they're calling the oldest colors on Earth. Dating back more than a billion years, the bright pink pigments are the remains of some of the earliest microscopic organisms that once inhabited an ancient ocean, and their discovery helps fill a gap in the fossil record.

The "colors" themselves are the molecular fossils of chlorophyll, a pigment that allows plants to photosynthesize sunlight into energy. They were discovered in marine black shale, sediments formed back when the area now known as the Sahara desert was a vast ocean.

In the ground, the fossils appear to be blood red or deep purple, and once extracted, crushed and diluted, they take on a bright pink color. But the study isn't just an ancient art project – the team was looking to help fill some gaps in the fossil record.

While it's known that life started out tiny and gradually grew into the diverse range of sizes and shapes we see today, exactly how that took place is still unknown. There aren't many fossils of microorganisms between the ages of 1.8 billion and 800 million years, so it's not clear how larger animals began to emerge around 600 million years ago.

The new discovery, dating back 1.1 billion years, is a neat first step towards plugging that hole. The pigments were produced by cyanobacteria, which would have been common during that time but probably wouldn't have been a rich enough food source to support much larger organisms.

"The precise analysis of the ancient pigments confirmed that tiny cyanobacteria dominated the base of the food chain in the oceans a billion years ago, which helps to explain why animals did not exist at the time," says Nur Gueneli, lead author of the study.

A few hundred million years later, though, algae began to spread, which could have supported larger and larger lifeforms.

"Algae, although still microscopic, are a thousand times larger in volume than cyanobacteria, and are a much richer food source," says Jochen Brocks, senior lead researcher on the study. "The cyanobacterial oceans started to vanish about 650 million years ago, when algae began to rapidly spread to provide the burst of energy needed for the evolution of complex ecosystems, where large animals, including humans, could thrive on Earth."

The research was published in the journal PNAS.

Source: Australian National University