Sunday, December 4

The world’s oldest food helps unlock the mystery of our earliest animal ancestors


The contents of the last meal eaten by the earliest known animals – which inhabited Earth more than 550 million years ago – has unearthed new clues about the physiology of our earliest animal ancestors, according to scientists at the Australian National University (ANU).

Fossil remains of animals found for the first time where the meteorite that killed the dinosaurs struck

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The animals belonging to the so-called biota of the Ediacaran period constituted the oldest large organisms in the world 575 million years ago. The ANU researchers, as reported by this institution in a press release, discovered that these animals fed on bacteria and algae from the seabed.

The findings, published this Tuesday in the magazine Current Biology, reveal more information about these strange creatures, including how they were able to consume and digest food. The scientists analyzed ancient fossils that retained phytosterol molecules (natural chemicals found in plants) from the animals’ last meal.

By examining the molecular remains of what they ate, the researchers were able to confirm that the slug-like organism, known as Kimberella, had a mouth and intestine and digested food in the same way as modern animals. They state that it was probably one of the most advanced creatures among the Ediacaran organisms.

The ANU team found that another animal, which grew up to 1.4 meters in length and had a rib-like pattern on its body, was less complex and had no eyes, mouth or intestine. Instead, the strange creature, called Dickinsonia, absorbed food through its body as it traversed the ocean floor.



“Weird bugs”

“Our findings suggest that the biota of the Ediacaran period animals, which lived on Earth before the ‘Cambrian explosion’ of modern animal life, were a mix of oddballs, such as Dickinsonia, and more advanced animals such as Kimberella, which they already had some similar physiological properties to humans and other living animals,” says lead author Ilya Bobrovskiy of the GeoForschungsZentrum in Potsdam, Germany.

Both Kimberella and Dickinsonia, which have a different structure and symmetry than today, are part of the Ediacaran biota family that lived on Earth some 20 million years before the ‘Cambrian explosion’, a major event that forever changed the world. course of evolution of all life on Earth. Bobrovskiy in 2018 recovered both the Kimberella and Dickinsonia fossils from steep cliffs near the White Sea, northwestern Russia, in the Arctic Ocean.

“Ediacaran organisms are really the oldest fossils and large enough to be visible to the naked eye. They are also our origin and that of all animals that exist today. These creatures are our deepest and most visible roots,” says Bobrovskiy, who conducted this research as part of his PhD at ANU.

Study co-author Professor Jochen Brocks, from the ANU Research School of Earth Sciences, said the algae are rich in energy and nutrients and may have been critical to the growth of Kimberella. “The energy-rich food may explain why the organisms of the Ediacaran biota were so large. Almost all earlier fossils were single-celled and microscopic in size,” says Professor Brocks.

Ediacaran organisms are our origin and that of all animals that exist today. These creatures are our deepest and most visible roots.

Ilya Bobrovsky

Using advanced chemical analysis techniques, the ANU scientists were able to extract and analyze the sterol molecules contained in the fossil tissue. Cholesterol is the hallmark of animals. That is how, in 2018, the ANU team was able to confirm that the Ediacaran biota is among our earliest known ancestors.

The molecules contained telltale signals that helped the researchers decipher what the animals ate in the lead up to their death. Professor Brocks notes that what was difficult was differentiating between the signals from the creatures’ own fat molecules, the remains of algae and bacteria in their intestines, and the decaying algae molecules from the ocean floor that were all together, present in the fossils.

“Scientists already knew that Kimberella left feeding marks by scratching at algae that covered the seafloor, suggesting that the animal had an intestine. But only after analyzing the molecules in Kimberella’s gut were we able to determine exactly what she ate and how she digested the food,” Brocks says. “Kimberella knew exactly which sterols were good for her and had an advanced gut fine-tuned to filter out all the rest.”

“This was a eureka moment for us; By using chemistry preserved in fossils, we can now make the contents of animal intestines visible, even if the intestine has long since decomposed. We then used this same technique on weirder fossils like Dickinsonia to find out how it fed, and we found that Dickinsonia had no intestine.”




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