Oxygen was once a scarce element on Earth during its first 2 billion years. Life at that time was rare and different from what it is today. It was only during the Great Oxidation Event that complex bacteria capable of photosynthesis stepped into the scene that everything changed.
But now, Science Alert reported that new gene-analyzing technology has provided new evidence that changes the timeline of Earth's evolution. The study suggests that it took the bacteria 400 million years to gobble sunlight and puff out oxygen to thrive during the early years of the planet.
That means organisms at that time were likely capable of photosynthesizing even before the Great Oxidation Event.
Evolution of Photosynthesis in Cyanobacteria
There are two competing narratives that try to explain the evolution of photosynthesis in cyanobacteria. First is that it is a natural process of converting sunlight into energy, which arrived in the evolutionary scene during the early times but progressed slowly. On the other hand, others think that photosynthesis is a quick process that happened like a wildfire.
A lot of the disagreement between scientists was on how fast the evolution of photosynthesis in cyanobacteria, and the different interpretations they had based on the fossil record.
According to Universe Today, cyanobacteria developed photosynthesis almost 500 years earlier than the Great Oxidation Event, between 3.4 and 2.9 billion years ago. However, there are a lot of gaps between the evolution of photosynthesis in cyanobacteria as well as the reshaping of the Earth's atmosphere.
MIT researchers have conducted a study to understand the gap and explore Earth's evolution. MIT scientist Greg Fournier and his colleagues measured oxidation in ancient rocks aged 3.5 billion years old and also added a new form of analysis to estimate the beginning of photosynthesis.
New Gene-Analyzing Technique Gives Hint to the Beginning of Photosynthesis
In the study, titled "The Archean Origin of Oxygenic Photosynthesis and Extant Cyanobacterial Lineages" published in the journal Proceedings of the Royal Society B, researchers combined molecular clock dating with horizontal gene transfer.
MIT News reported that the gene-analyzing technique showed that all species of cyanobacteria alive today have a common ancestor that evolved around 2.9 billion years ago, and from other bacteria around 3.4 billion years ago. They likely developed their photosynthetic ability during the Archeon Eon.
Moreover, their analysis also showed that before the Great Oxidation Event, cyanobacteria experiences a burst of diversification that could have tipped the Earth into the beginning of the event and launched oxygen into Earth's atmosphere.
The study sheds light on the oxygenation history of Earth in novel ways that provide vital constraints on the patterns and controls of the earliest oxygenation of oceans and the atmosphere. Fournier said that he plans to apply the horizontal gene transfer beyond cyanobacteria to investigate the origins of other species.
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