Researchers have discovered 1.6 billion-year-old eukaryotic organisms, the Protosterol Biota, believed to be Earth’s first predators. These ancient creatures, found through fossil fat molecules in ancient rocks, were more complex than bacteria, predating and likely shaping early marine ecosystems. This discovery challenges previous theories of a predominantly bacterial ancient ocean.

Our view of our oldest relatives may change if researchers find a “lost world” of ancient species that existed in Earth’s waterways at least 1.6 billion years ago.

These tiny critters, also referred to as the “Protosterol Biota,” are eukaryotes, a group of organisms. The “powerhouse” of the cell, the mitochondria, are part of the intricate cell structure of eukaryotes, as is the nucleus, which serves as the “control and information centre.”

Fungi, plants, animals, and single-celled organisms like amoebae are examples of modern eukaryotes that live on Earth. The Last Eukaryotic Common Ancestor (LECA) is the common ancestor of all nucleated animals, including humans. More than 1.2 billion years ago, LECA was alive.

Researchers from The Australian National University (ANU) made the Protosterol Biota discovery, which was reported in Nature. These critters may have been the planet’s earliest predators, say the researchers.

These extinct animals were prevalent in marine habitats all across the world and likely influenced ecosystems for a significant portion of Earth’s history. The Protosterol Biota predated the emergence of any animals or plants by at least a billion years, according to the researchers.

“Molecular relics of the protosterol biota found in rocks dating back 1.6 billion years appear to be the earliest survivors of our own ancestry; they existed even before LECA. These ancient organisms were prevalent in marine ecosystems all over the planet and likely influenced ecosystems for a significant portion of Earth’s history, according to Dr. Benjamin Nettersheim, who received his PhD from ANU and is currently located at the University of Bremen in Germany.

Researchers believed that because modern eukaryotic organisms are so strong and dominating now, they should have dominated Earth’s ancient oceans more than a billion years ago.

Although these early eukaryotes’ physical remains are relatively rare, scientists have long looked for fossilised proof of them. Ancient waters on Earth seemed to be mostly made up of bacterial soup.

Why didn’t our highly skilled eukaryotic ancestors take over the world’s prehistoric rivers is one of the biggest mysteries of early evolution that scientists have been trying to solve. Where did they skulk in?

“Our research contradicts this theory. We demonstrate that the protosterol biota were present in great abundance in the world’s earliest oceans and lakes despite being hidden in plain sight. Up until today, scientists just didn’t know where to look for them.

The Protosterol Biota were undoubtedly more complicated than bacteria and presumably larger, according to Professor Jochen Brocks from the Australian National University (ANU), who made the finding with Dr. Nettersheim. However, it is unknown what they looked like.

According to Professor Brocks, they may have been the earliest predators on Earth, hunting and consuming microbes.

Professor Brocks asserts that these organisms flourished between roughly 1.6 billion years ago and 800 million years ago.

The ‘Tonian Transformation’ marked the end of this stage in Earth’s evolutionary history and marked the emergence of more sophisticated nucleated creatures like fungi and algae. However, the precise date of the Protosterol Biota’s extinction is unknown.

According to Professor Brocks, “The Tonian Transformation is one of the most significant ecological turning points in the history of our planet.”

Perhaps the Protosterol Biota had to vanish a billion years earlier to make room for modern eukaryotes, just as the dinosaurs had to go extinct so that our animal ancestors could become big and numerous.

The discovery was made when scientists examined fossilised fat molecules that were found inside a 1.6 billion year old rock that originated at the ocean floor close to what is now Australia’s Northern Territory. Early complex animals that arose before LECA and have since gone extinct may have existed because of the molecules’ primitive chemical structure.

We would have never been aware that the protosterol biota existed if not for these compounds. Our new finding disproves the widespread belief that early waters were dominated by microorganisms, according to Dr. Nettersheim.

Scientists have been ignoring these molecules for forty years because they don’t fit the mould of usual molecular search images, according to Professor Brocks.

But after we found what we were looking for, we found that hundreds of additional rocks, retrieved from billion-year-old waterways all around the planet, were also dripping with the same fossil molecules.

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