World's Oldest Meal From More Than 550 Million Years Ago Reveals New Clues on the Physiology of Earliest Animals

Researchers from the Australian National University (ANU) analyzed the contents of the final meal of the Ediacaran biota, the world's oldest big creatures that lived 575 million years ago, and revealed fresh clues about the physiology of the earliest animal ancestors.

The study, titled "Guts, gut contents, and feeding strategies of Ediacaran animals" published in Current Biology, unearths more about these strange creatures, such as how they ate and digested food.

Examining the Molecular Components of the World's Oldest Meal

According to SciTech Daily, the researchers examined old fossils that included intact phytosterol molecules, which are natural chemical compounds found in plants, from the last meal of the earliest animal ancestors.

Analyzing the molecular remains of what they ate confirmed that the slug-like organism, known as Kimberella, had a mouth and a stomach and digested food in the same manner that modern animals do. It was most certainly one of the most sophisticated Ediacaran species.

Another species discovered by the ANU team, which grew up to 1.4 meters in length and had a rib-like pattern imprinted on its body, was less complicated and lacked eyes, mouth, and stomach. Instead, the strange species known as Dickinsonia absorbed nourishment via its body as it moved over the ocean floor.

Lead author Dr. Ilya Bobrovskiy explained that the findings suggest that the animals of the Ediacara biota, which lived on Earth prior to the 'Cambrian Explosion' of modern animal life, were a mix of Dickinsonia and Kimberella, which already had some physiological properties similar to humans and other modern animals.

Both species have a structure and symmetry unique to any animal today and are part of the Ediacara biota from 20 million years before the Cambrian Explosion. Dr. Bobrovskiy emphasized that Ediacara biota is the oldest fossils large enough visible to the naked eye and is the origin of all animals and even humans.

Algae are high in energy and nutrients and may have aided Kimberella's growth, says study co-author Professor Jochen Brocks of the ANU Research School of Earth Sciences. The high-energy content of algae could perhaps explain why Ediacara biota are large.

Eureka Moment: Identifying the World's Oldest Meal

The ANU scientists extracted and analyzed the sterol molecules found in prehistoric tissue using modern chemical analysis techniques to determine what the animals ate before they perished, Science Daily reported.

The tricky aspect, according to Professor Brocks, was distinguishing between the traces of the organisms' fat molecules, the algal and bacterial residues in their intestines, and the decaying algal molecules from the ocean floor, which were all entombed together in the fossils.

Professor Brocks explained that it wasn't until they analyzed the chemicals in Kimberella's gut that they were able to discover what it was eating and how it processed food. Kimberella understood exactly which sterols were beneficial for it and had an advanced fine-tuned gut to filter out all the others.

It was a Eureka moment for them as they can now make the gut contents of animals visible even if the gut has since long decayed. Then they used the same technique on Dickinsonia to know how it was eating and found that it does not have a gut.