You probably wouldn’t have much to see if you’d go back in time 1.1 billion years. Multicellular life was just starting to develop, and plants were yet to develop. But life, in its primitive, early stages, was already very active. For instance, a group of sea organisms was busy producing chlorophyll — and researchers have now found fossilized molecules of these organisms, which they believe to be the oldest colored molecules we’ve ever found.
Biogeochemistry lab manager Janet Hope holds a vial of colored porphyrins (pink colored liquid), which researchers believe to be some of the oldest pigments in the world. Photograph: Lannon Harley/Australian National University.
Naturally, most things are colored, but it took a while for life to be able to develop its own hues.
“Of course you might say that everything has some colour,” said the senior lead researcher, Associate Prof Jochen Brocks from the Australian National University (ANU). “What we’ve found is the oldest biological colour.”
It all started with researchers grinding samples of shale rock. ANU Ph.D. student, Dr. Nur Gueneli, was running an organic solvent through the powdered rock, a process similar to what you’d see in a coffee machine. Gueneli was thrilled when she realized what she had stumbled upon.
“I heard her screaming in the lab when it came out, and she ran into my office,” Asst Prof Brocks told the BBC. “At first I thought it had been contaminated. It is just amazing that something with a biological colour can survive for such a long time.”
Subsequent analysis revealed that the pigment was produced by cyanobacteria.
This doesn’t mean that we know what color the cyanobacteria had when they were living, however. For instance, a dinosaur bone would have its own color, but that doesn’t tell you anything about the color of its skin.
The finding doesn’t only go skin deep. While it’s always exciting to discover something colored and cool, the discovery will also help solve an important puzzle about life: why large, complex creatures took so long to develop.
The Earth as a planet is about 4.6 billion years old, but more complex creatures like seaweed only emerged some 600 million years ago. Brocks says that the cyanobacteria producing these pigments were very small — even 1,000 times smaller than microscopic algae alive today. So for animals existing at the time, the cyanobacteria didn’t provide much of a meal — which means no stable food chain. In other words, you can only get big if there are big enough things to eat around you.
The study has been published in journal Proceedings of the National Academy of Science of the United States of America.
