World's Oldest Biological Colors Discovered in Billion-Year-Old Rocks Under the Sahara

Biogeochemistry lab manager Janet Hope from the ANU Research School of Earth Sciences holds a vial of pink colored porphyrins representing the oldest intact pigments in the world. The Australian National University

Scientists have discovered the oldest intact biological colors on Earth, according to research published in the journal Proceedings of the National Academy of Sciences.

An international team led by researchers from the Australian National University (ANU) extracted 1.1-billion-year-old bright pink pigments from ancient rocks deep below the Sahara Desert in Mauritania, West Africa.

The pigments, which were found in a marine black shale deposit, are more than 500 million years older than any previously known pigments, said Nur Gueneli, lead author of the study from ANU's Research School of Earth Sciences.

"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," Gueneli said in a statement.

The color of the fossils ranges from blood red to deep purple in concentrated form, and bright pink when diluted with water.

The new findings shed new light on the evolution of life on Earth.

For their research, the scientists crushed the black shale into powder, before extracting and analyzing the molecules from the ancient organisms. The analysis confirmed that tiny cyanobacteria—a type of bacteria that obtain their energy through photosynthesis—dominated the base of the food chain in Earth's early oceans, billions of years ago.

This could help to explain why animals did not exist at the time, according to the researchers. The evolution of larger, active organisms was likely held back by a limited supply of larger food particles, such as algae, at this time.

"Algae, although still microscopic, are a thousand times larger in volume than cyanobacteria, and are a much richer food source," Jochen Brocks, also from ANU's earth sciences school, said.

"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."