Ancient Eukaryotic Organisms Unearthed: Unlocking the Secrets of Earth’s First Predators

Researchers have made a groundbreaking discovery, unveiling the existence of eukaryotic organisms dating back 1.6 billion years. Known as the Protosterol Biota, these ancient creatures are believed to be Earth’s initial predators, challenging prior assumptions about the composition of early marine ecosystems. Fossilized fat molecules found in ancient rocks led to the revelation of these complex organisms that preceded bacteria, reshaping our understanding of the ancient oceans.

The revelation of this “lost world” offers crucial insights into our earliest ancestors and their habitat, revolutionizing our comprehension of early life on Earth. The Protosterol Biota, microscopic organisms categorized as eukaryotes, possess intricate cell structures encompassing mitochondria, the cell’s powerhouse, and a nucleus serving as the control and information center.

Modern-day eukaryotes include a diverse range of organisms such as fungi, plants, animals, and single-celled entities like amoebae. The lineage of humans and all nucleated creatures can be traced back to the Last Eukaryotic Common Ancestor (LECA), which thrived over 1.2 billion years ago.

The Protosterol Biota’s discovery, published in the prestigious journal Nature, was a result of research conducted by a team from The Australian National University (ANU). These ancient organisms likely functioned as the earliest predators on Earth, significantly shaping marine ecosystems worldwide. Astonishingly, they existed at least one billion years prior to the emergence of any animal or plant species.

Dr. Benjamin Nettersheim, who completed his PhD at ANU and now works at the University of Bremen in Germany, emphasized the significance of this finding: “The molecular remnants of the Protosterol Biota found in 1.6-billion-year-old rocks appear to be the oldest traces of our own lineage. These ancient creatures were pervasive in marine ecosystems worldwide, playing a fundamental role throughout Earth’s history.”

The prevailing assumption was that modern eukaryotes, with their impressive capabilities, would have conquered the ancient oceans over a billion years ago. Yet, the search for fossilized evidence of these early eukaryotes has been challenging, as physical remains are exceptionally scarce. Earth’s ancient oceans seemed to be dominated by bacteria, presenting a perplexing puzzle for scientists: Where were our highly capable eukaryotic ancestors?

“Our study overturns this theory entirely. We demonstrate that the Protosterol Biota was hiding in plain sight, abundantly populating ancient oceans and lakes around the world. Scientists were simply unaware of how to identify them—until now,” Dr. Nettersheim explained.

Professor Jochen Brocks from ANU, who collaborated with Dr. Nettersheim on this discovery, suggests that the Protosterol Biota surpassed bacteria in complexity and size, although their physical appearance remains unknown. He proposed that these organisms likely hunted and consumed bacteria, making them the first predators on Earth.

These creatures thrived from approximately 1.6 billion years ago until about 800 million years ago, with their extinction marking a significant ecological turning point in Earth’s history, referred to as the “Tonian Transformation.” During this era, more advanced nucleated organisms like fungi and algae began to flourish, eventually making way for modern eukaryotes. The exact timeline of the Protosterol Biota’s extinction, however, remains uncertain.

To make this groundbreaking discovery, researchers examined fossilized fat molecules embedded within a 1.6-billion-year-old rock, formed at the bed of an ancient ocean near Australia’s Northern Territory. These molecules possessed a primordial chemical structure, providing clues to the existence of complex creatures that predated LECA and have since vanished.

“Without these molecules, we would have remained unaware of the existence of the Protosterol Biota. Early oceans appeared to be primarily inhabited by bacteria, but our new discovery indicates that this was likely not the case,” Dr. Nettersheim remarked.

Professor Brocks added, “For four decades, scientists overlooked these molecules because they deviated from typical search criteria. However, once we knew what to look for, we discovered similar fossil molecules oozing from numerous rocks taken from billion-year-old waterways across the globe.”

The study represents a collaborative effort involving scientists from Australia, France, Germany, and the United States. Dr. Nettersheim conducted this research as part of his PhD at ANU before joining the University of Bremen.

Title: Ancient Eukaryotic Organisms Unearthed: Unlocking the Secrets of Earth’s First Predators

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More about Ancient organisms

• Nature: “Lost world of complex life and the late rise of the eukaryotic crown”
• The Australian National University: “Scientists Discover ‘Lost World’ of Our Early Ancestors in Billion-Year-Old Rocks”