Photosynthesis, the process used by plants and other organisms to convert energy from light to chemical energy, maintains oxygen levels in the atmosphere that is necessary for life on earth. Cyanobacteria, the blue-green algae, that evolved photosynthesis were thought to have appeared 2.5 billion years ago when the 'Great Oxidation Event' (a spike in oxygen levels) happened.
But a new research suggests that first photosynthetic organisms lived on earth three billion years ago, long before the 'Great Oxidation Event'.
Noah Planavsky, a geochemist at Yale University and his colleagues 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.
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"Our study is telling you that there was localised cyanobacteria production in the oceans," he was quoted as saying.
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"The two studies are quite complementary," Planavsky said in the study that appeared in the journal Nature Geoscience.
Source-IANS