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Organisms called Protosterol Biota lived 1.6 billion years ago

Diving deep into the realm of life’s origin, scientists have recently unearthed an enthralling discovery. They have found evidence of an ancient “lost world” – microscopic creatures that inhabited Earth’s waterways as far back as 1.6 billion years ago. This discovery is set to redefine our understanding of the earliest known lifeforms on Earth and their connection to our ancestral lineage.

These ancient organisms, labeled as the “Protosterol Biota,” belong to a broad family of life known as eukaryotes. Unlike their simpler bacterial cousins, eukaryotes exhibit a more intricate cell structure. Their cells house vital components such as mitochondria, famously dubbed the “powerhouse” of the cell, and a nucleus serving as the “control and information center.”

Eukaryotes of today have adopted various forms – fungi, plants, animals, and single-celled organisms like amoebae are some of the examples. Interestingly, humans, along with all other nucleated beings, trace their ancestry back to the Last Eukaryotic Common Ancestor (LECA), an organism that existed more than 1.2 billion years ago.

Protosterol Biota may have been Earth’s first predators

However, this recent discovery, which was published in the journal Nature, unveils that the Protosterol Biota thrived even before LECA. Scientists from Australian National University (ANU), who made this revelation, propose that these organisms might have been the Earth’s inaugural predators.

Dr. Benjamin Nettersheim, a former PhD student at ANU now at the University of Bremen in Germany, noted that these ancient beings were quite prolific in marine ecosystems around the world. He stated, “Molecular remains of the Protosterol Biota detected in 1.6-billion-year-old rocks appear to be the oldest remnants of our own lineage – they lived even before LECA.”

“Scientists have long searched for fossilised evidence of these early eukaryotes, but their physical remains are extremely scarce,” explained Dr. Nettersheim. “Our study flips this theory on its head. We show that the Protosterol Biota were hiding in plain sight and were in fact abundant in the world’s ancient oceans and lakes all along.”

Further elucidating on the nature of these ancient organisms, Professor Jochen Brocks from ANU, who collaborated with Dr Nettersheim on this discovery, suggests that the Protosterol Biota were certainly more intricate and probably larger than bacteria. “We believe they may have been the first predators on Earth, hunting and devouring bacteria,” said Professor Brocks. 

When Protosterol Biota ruled the Earth

According to Professor Brocks, the reign of these creatures began around 1.6 billion years ago and lasted until about 800 million years ago. This was a period in Earth’s evolutionary timeline that culminated in the “Tonian Transformation.” During this significant juncture, more advanced nucleated organisms such as fungi and algae began to prosper.

“The Tonian Transformation is one of the most profound ecological turning points in our planet’s history,” said Professor Brocks. “Just as the dinosaurs had to go extinct so that our mammal ancestors could become large and abundant, perhaps the Protosterol Biota had to disappear a billion years earlier to make space for modern eukaryotes.”

How the research team made this discovery

The scientists made this groundbreaking discovery by studying fossil fat molecules tucked away inside a 1.6-billion-year-old rock that had formed at the bottom of the ocean near present-day Australia’s Northern Territory. These molecules, with a primordial chemical structure, suggested the presence of early complex creatures that evolved before LECA and had since vanished.

“Without these molecules, we would never have known that the Protosterol Biota existed. Early oceans largely appeared to be a bacterial world, but our new discovery shows that this probably wasn’t the case,” said Dr. Nettersheim.

These fossil molecules have been overlooked for decades, as they did not fit the typical molecular search parameters used by scientists. 

“Scientists had overlooked these molecules for four decades because they do not conform to typical molecular search images,” said Professor Brocks. “But once we knew what we were looking for, we discovered that dozens of other rocks, taken from billion-year-old waterways across the world, were also oozing with similar fossil molecules.”

Dr Nettersheim, who undertook this analysis as a part of his PhD at ANU before moving to the University of Bremen, was not alone in this endeavor. This seminal work involved a multinational collaboration that brought together scientists from Australia, France, Germany, and the United States.

This remarkable discovery of the Protosterol Biota, revealing an unknown chapter of Earth’s evolutionary narrative, is a testament to the boundless scope of scientific exploration. 

As we delve deeper into the mysteries of the past, we gain valuable insights that help shape our understanding of the present and foresee the trajectory of life’s future evolution. The story of our ancient ancestors might be far from complete, but this discovery serves as a fascinating new piece of the puzzle.

More about the earliest life on Earth

Life on Earth started at least 3.5 billion years ago, as evidenced by the discovery of fossils of microscopic organisms in rocks of that age. 

The very first lifeforms were likely simple, single-celled organisms, analogous to bacteria. This era, known as the Archean Eon, was characterized by a lack of oxygen in the Earth’s atmosphere and high levels of volcanic activity.

Prokaryotes were probably first

Among the earliest forms of life were prokaryotes. These are simple, single-celled organisms that lack a nucleus or other membrane-bound organelles. The prokaryotes include bacteria and archaea, two domains of life that are still present today. 

Many prokaryotes are extremophiles, capable of surviving in harsh environments such as hydrothermal vents and acidic springs, which were common during Earth’s early history.

Significant leap forward when eukaryotes arrived

Life remained microscopic and single-celled for billions of years, a time span known as the Precambrian. Then, around 2.1 billion years ago, a significant evolutionary leap occurred: the emergence of eukaryotes. 

These are organisms with complex cells that have a nucleus and other membrane-bound organelles. The first eukaryotes were likely single-celled, like their prokaryotic predecessors, but they represented a significant increase in biological complexity.

Photosynthesis changes everything

The invention of photosynthesis by cyanobacteria, a type of prokaryote, transformed the Earth’s atmosphere by filling it with oxygen. This event, known as the Great Oxygenation Event, occurred around 2.45 billion years ago. The rise of oxygen levels in the atmosphere allowed for the evolution of more complex, multicellular organisms.

Around 600 million years ago, during the Ediacaran Period, the first multicellular animals appeared. These strange creatures bore little resemblance to modern animals, and many of them belonged to groups that have since gone extinct. 

Cambrian explosion 

It wasn’t until the Cambrian explosion, about 540 million years ago, that the ancestors of most modern animal groups emerged. This event was characterized by a rapid increase in biodiversity and complexity.

So, the journey of life on Earth began with simple, single-celled organisms and, over billions of years, evolved into the complex web of biodiversity we see today. This ongoing process of evolution continues to shape life on our planet.

Image Credit: Orchestrated in MidJourney by TA 2023


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