New York: It was generally believed that cyanobacteria, the blue-green algae, that evolved photosynthesis appeared 2.5 billion years ago when the 'Great Oxidation Event' (a spike in oxygen levels) happened.
But now a new research suggests that first photosynthetic organisms lived on earth three billion years ago, long before the 'Great Oxidation Event'.
This research was undertaken by Noah Planavsky, a geochemist at Yale University and his colleagues who analysed levels of molybdenum chemical and iron in 2.95-billion-year-old rocks from South Africa.
The metals serve as markers of photosynthesis.
Molybdenum isotopes, or elements with the same number of protons but a different number of neutrons, track manganese oxidisation - a process that requires high levels of oxygen, Planavsky said.
The rocks were laid down in water, in a shallow ocean setting near the shore.The chemical traces in the rocks indicate cyanobacteria were producing oxygen in ocean surface water, Planavsky added.
“Our study is telling you that there was localised cyanobacteria production in the oceans,” he further added.