It's easy to forget that the smallest things are the most significant. Early life on Earth was hectic, adapting to gasping worlds as mankind pursued stars. Recent research suggests that some bacteria learned to use oxygen long before it became a ubiquitous element in our atmosphere.
The research, published in Science on April 4, followed the early development of oxygen-using bacteria with the help of artificial intelligence. Bacteria, the research found, had learned to cope with oxygen approximately 900 million years before Earth's atmosphere was full of it.
Bacteria have been around since the dawn of time
The planet Earth thawed approximately 4.5 billion years ago. The Moon was created when a Mars-sized object crashed. If there was life at that time, it likely was eradicated.
Then, bacteria were the only life on Earth. For eighty percent of our world's history, these one-celled organisms ruled. Although they are not complex, bacteria do not make much of a mark. They are boneless and hard to fossilize.
Researchers struggled to track their development because of it. But computer machine learning and DNA comparison are being employed to assist in the compilation of a timeline. It was led by researchers at ETH Zurich and the University of Queensland.
In order to determine which bacteria utilize oxygen, they created an AI model. Genes give strong clues. The metabolic markers of oxygen-dependent and oxygen-independent bacteria are different.
Scientists could follow the oxygen-consuming trait back in time using these methods. Well before the "Great Oxidation Event" (GOE), which took place 2.4 billion years ago, they found evidence that some bacteria were consuming oxygen.
The Great Oxidation Event irreversibly changed life on our planet
There was little oxygen on Earth before the GOE. Cyanobacteria made a change with photosynthesis when they first evolved it. They created oxygen as a waste product when they used energy from sunlight to produce energy.
Oxygen had built up over millions of years in the air. Early microbes were poisonous to oxygen. Many became extinct. Others retreated or adapted underground, where oxygen was out of reach.
The GOE was used as a landmark by researchers because it can be dated. They were then able to calculate the first occurrence of oxygen-utilizing bacteria.
They learned that around 900 million years ago, some bacteria had learned to utilize oxygen. That was millions of years before oxygen was present in great quantities in the atmosphere.
Surprisingly, the study also revealed that oxygen was probably used by cyanobacteria prior to photosynthesis. This turn of events alters our perception of their evolution.
AI uncovers the secret history of microorganisms
Geology, fossils, DNA, and machine learning were all mixed by the scientists. This method created a more lucid chronology of the evolution of bacteria throughout Earth's history.
With analysis of ancient bacterial genomes, the model predicted earlier oxygen use.
Life's deep-time adaptations were mapped by these genomic "snapshots."
The method, the researchers say, rewrites history in how we consider early life. It shows how microbes evolved to suit the changing environment on Earth way before we ever thought it possible.
The research shows how modern-day instruments can uncover long-lost secrets. Secrets can be uncovered hidden in DNA from even the smallest cells.
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