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A geology team led by theUniversity of California in Riverside (USA) has discovered the earliest common ancestor of most animals known today, including humans.
The results have been published in the journalPNAS.
The fossil was discovered in Nilpena, in the interior of southernAustralia and, according to the dating of the rocks in which it was found, it has more than555 million years, during the Proterozoic eon.
This species, calledIkaria wariootia, is similar to a worm between two and seven millimeters and is the bilaterian - the first organism withbilateral symmetry- oldest discovered.
"This means that it had a different front and rear end, which is the type of organization that leads to the variety of animals with mouths and anus that exist today," he explains to SINC.Scott evans, a researcher at the American university and one of the authors of the work.
The firstmulticellular organismsLike sponges and algae, they had variable shapes.
This group, known as theBiota the Ediacaran period (between 635 and 542 million years ago), it contains the oldest fossils of complex multicellular organisms.
However, most of them are not directly related to current animals.
Critical step in the evolution of animal life
According to Evans, the development of bilateral symmetry was a critical step in the evolution of animal life, as it provides organisms with the ability to move purposefully and a successful way to organize their bodies.
A multitude of animals, from worms, dinosaurs even humans, they are constituted with that same basic bilateral body plan.
Now this work reveals thatIkaria it is the oldest animal with bilateral symmetry and, therefore, the ancestor of organisms with this type of organization.
“It had been predicted that something like this should exist based on the burrows it leftIkaria, callsHelminthoidichnites, and in modern animal genetic studies. However, it was unlikely that we would find and identify them in the fossil record, ”says the geologist.
But the team ended up finding it using the novel technology of3D laser scanning.
With this technique "we only see an impression or mold of what the exterior of the organism would have been like", he clarifies, but with this they have been able to observe in the burrowstransverse ridges in the shape of 'V'.
This suggests thatIkaria it moved by contracting the muscles of its body like a worm, which is known asperistaltic locomotion.
"We also observed in the burrows that it was heading for food and oxygen, which tells us that it had the ability to sense things in its environment," adds Evans.
According to the researcher, “or really shocking is thatIkaria helps to confirm what was predicted about the last common ancestor of all bilaterians.
"The ability to match hypotheses based on the genetics of modern organisms with a fossil more than 500 million years old is a surprising and unexpected finding," he concludes.
Scott D. Evans, Ian V. Hughes, James G. Gehling, and Mary L. Droser. "Discovery of the oldest bilaterian from the Ediacaran of South Australia”. PNAS (March 23, 2020). DOI: 10.1073 / pnas.2001045117.