Paramecium bursaria under a microscope. All creatures whose cells house a nucleus, including Paramecium bursaria, can be traced back to a common ancestor called the Last Eukaryotic Common Ancestor (LECA).


Ancient organisms that crossed Earth’s waterways at least 1.6 billion years ago don’t seem to have much in common with humans, but we couldn’t have evolved without the eukaryotes called Protosterol. Biota. A team of researchers has discovered a “lost world” of these ancient organisms inside a rock that had formed on the ocean floor near what is now Australia’s Northern Territory. The findings are described in a study published June 7 in the journal Nature.

[Related: Fossil trove in Wales is a 462-million-year-old world of wee sea creatures.]

Eukaryotes like Protosterol Biota have a complex cell structure that includes mitochondria (known to many as the powerhouse of the cell) and a nucleus that acts as the cell’s control and information center. Modern eukaryotes on Earth include plants, fungi, animals, and single-celled organisms like amoebas. All creatures whose cells house a nucleus can trace their lineage over 1.2 billion years ago to the last eukaryotic common ancestor (LECA).

According to the researchers, Protosterol Biota may have been the first predator on Earth. They inhabited marine ecosystems around the world and likely played an important role in ecosystem formation. Protosterol Biota also lived at least a billion years before any animal or plant species emerged.

“Molecular remnants of protosterol biota detected in 1.6 billion year old rocks appear to be the oldest remnants of our own lineage – they even predated LECA. These ancient creatures were abundant in marine ecosystems around the world and likely shaped ecosystems for much of Earth’s history,” said co-author and biogeochemist from the University of Bremen in Germany, Benjamin Nettersheim. , in a press release. “Modern forms of eukaryotes are so powerful and dominant today that researchers thought they should have conquered Earth’s ancient oceans more than a billion years ago.”

Fossilized remains of eukaryotes are very rare, even though modern eukaryotes are very powerful and dominant today. Researchers thought they should have conquered the ancient oceans over a billion years ago, and evolutionary scientists tried to piece together a puzzle. Why didn’t our highly capable eukaryotic ancestors eventually dominate the waterways of the world, and where were they hiding?

“Our study overturns this theory. We show that the protosterol biota was hiding in plain sight and was in fact abundant in the ancient oceans and lakes of the world from the beginning. Scientists just didn’t know how to look for them — until now,” Nettersheim said.


[Related: Scientists genetically engineered prehistoric proteins to detect diseases.]

Protosterol Biota flourished from about 1.6 billion years ago until about 800 million years ago and were more complex than bacteria. They were also probably larger than bacteria, but scientists still don’t know what they looked like. They may have been Earth’s first predators, hunting and munching on smaller bacteria.

The team studied fossil fat molecules found inside rocks in Australia. The molecules had a primordial chemical structure that offered clues to the existence of complex early creatures that evolved before LECA and have since disappeared.

“Without these molecules, we would never have known Protosterol Biota existed. The early oceans largely appeared to be a bacterial world, but our new discovery shows that was probably not the case,” Nettersheim said.

During a period called the Tonian Transformation, which took place around 1,000 to 720 million years ago, more advanced nucleated organisms, including algae and fungi, began to thrive. However, scientists still know exactly when Protosterol Biota died out.

“The Tonian Transformation is one of the most profound ecological turning points in the history of our planet,” Jochen Brocks, study co-author and geobiologist at the Australian National University, said in a statement. “Just as dinosaurs had to die out so our mammalian ancestors could grow large and abundant, perhaps the protosterol Biota had to die out a billion years earlier to make way for modern eukaryotes.”

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