One of the oldest ancestors of complex life on Earth discovered, 1.6 billion years old

Dmytro IvancheskulLife
Protosterol biota
Artistic representation of the ''protosterol biota'' living on a bacterial mat on the ocean floor. Source: Australian National University/collage by OBOZREVATEL

Traces of organisms that lived in the Earth's ancient waterways about 1.6 billion years ago have been found in fossilised ocean rock near the northern territory of Australia. The discovery may change the way scientists think about our earliest ancestors.

This is stated in a study published in the journal Nature. We are talking about eukaryotes - organisms with a complex cellular structure that includes mitochondria and nucleus. The former is responsible for energy production, and the latter is a kind of control and information centre.

All species of animals, including humans, as well as plants, fungi, and unicellular organisms such as amoebae, evolved from eukaryotic cells. Each of these organisms can trace their lineage back to the last eukaryotic common ancestor (LECA), which lived more than 1.2 billion years ago.

However, there has been no evidence of the existence of earlier eukaryotes. Now, researchers from the Australian National University (ANU) have described a "protosterol biota" that has been found in fossilised fat molecules in rocks dating back 1.6 billion years. These fats have a "chemical signature" that indicates that they originated from now extinct ancient eukaryotes.

The new discovery represents the oldest remnant of our species and is the source of all modern eukaryotic forms.

The scientists explained that they had previously been unable to detect these ancient organisms because they were looking for them using compounds secreted by modern eukaryotes. This time, they used a chemical component from earlier stages of microbial metabolism as a basis.

"Protosterol biota has been hiding in plain sight and has actually been widespread in the world's ancient oceans and lakes all along. Scientists just didn't know how to look for them - until now," explained study co-author Dr Benjamin Nettersheim of the University of Bremen in Germany.

After the discovery, scientists checked data from dozens of other rocks taken from waterways that existed around the world billions of years ago and found that they were also saturated with similar fossil molecules. Traces have been found in ancient waterways, including those in West Africa, Scandinavia and China.

The oldest samples date back to 1.64 billion years, but it is possible that biota will be found in older rocks when they are examined.

The first life on Earth appeared three to four billion years ago and was prokaryotic. These microbes lack a nucleus and other cell organelles. Prokaryotes make up the two other major branches of life on Earth besides eukaryotes - bacteria and archaea.

After studying the discovery, the scientists concluded that the protosterol biota was more complex than the bacteria that existed at the time and probably larger in size.

"We believe that they may have been the first predators on Earth to hunt and eat bacteria," suggested the study's first author, ANU professor Jochen Brox.

He believes that the protosterol biota flourished from about 1.6 billion to 800 million years ago.

Earlier, OBOZREVATEL reported that scientists for the first time managed to reconstruct the skull of Crassigyrinus scoticus, an animal that looks like modern crocodiles and was one of the most fearsome predators 330 million years ago. Scientists unofficially call it the tadpole from hell.

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