For most animals on earth, breathing is synonymous with life. However, our planet was deficient in oxygen for the first 2 billion years.
The earth cannot be said to be lifeless at this time, but life is rare and very different from what we know today.
Everything began to change until more complex bacteria with photosynthetic ability appeared on the scene, which scientists call the Great Oxidation phenomenon. But when did that happen? How did everything vibrate?
A new method of genetic analysis has provided recommendations for a new chronology. It is estimated that it took 400 million years for bacteria to take in sunlight and expel oxygen before life actually flourished.
In other words, there may have been photosynthetic organisms on our planet long before the Great Antioxidant event.
“In evolution, things always start small.” To explain Greg Fourier, geologist at the Massachusetts Institute of Technology.
“There is evidence for early oxygen photosynthesis – the most surprisingly important discovery in the evolution of the Earth – which took hundreds of millions of years to ascend.”
There are currently two competing accounts to explain the development of photosynthesis in a particular bacterium called cyanobacteria. Some believe that the natural process of converting sunlight into energy appeared at the very beginning of the evolutionary stage, but that it “slowly melted”. Others believe that photosynthesis developed later, but “it’s like fire.”
Most of the controversy arises from assumptions about the rate of bacterial growth and the different interpretations of the fossil record.
So Farnier and his colleagues added another type of analysis. In rare cases, bacteria sometimes inherit genes from other, closely related organisms, but not from their parents. This can happen when another cell “eats” and puts other genes in its gene.
Scientists can use this information to determine the relative age of different groups of bacteria; For example, those who stole genes had to adapt to species that existed at the same time.
These relationships can be compared to more specific dating efforts, such as molecular clock models that use the genetic sequences of organisms to track the history of genetic mutation.
For this purpose, the researchers tamed the genes of thousands of bacterial species, including cyanobacteria. They were looking for horizontal gene transfer events.
In total, they identified 34 clear examples. When comparing these examples with six molecular clock models, the authors considered one of them to be consistently more relevant. By selecting this form of compound, the team estimated the lifespan of the photosynthetic bacteria.
Results show that all blue-green algae living today have a common ancestor, which was about 2.9 billion years ago. Meanwhile, the ancestors they The ancestors of non-photosynthetic bacteria differed about 3.4 billion years ago.
Photosynthesis may have formed somewhere between these two dates.
According to the team’s preferred evolutionary model, photosynthesis could have occurred at least 360 million years before the cyanobacterial geosynchronous orbit. If they are correct, it supports the “slow integration” hypothesis.
“This new paper sheds a whole new light on the history of the Earth’s oxygen supply, linking fossil record to genetic data in new ways, including horizontal gene transfer.” He says Timothy Lions, biochemist at the University of California, Riverside.
“The findings speak to the beginnings of bio-oxygen production and its environmental significance, which provide biological barriers to early marine oxidation and subsequent accumulation of samples and controls in the atmosphere.”
The authors hope to use similar genetic analysis methods to analyze organisms other than cyanobacteria in the future.
The study was published Royal Society Articles b..