Ikaria wariootia would have lived more than 555 million years ago and had a bilateral body, just like humans.
Geologists at the University of California, United States, have found what may be the first ancestor of animals we know today, including humans. Called Ikaria wariootia, the microscopic organism is the first bilaterian organism – with front and back, two symmetrical sides, and openings at both ends connected by an intestine.
The article, published in the scientific journal Proceedings of the National Academy of Sciences, estimates that the creature would have lived more than 555 million years ago. The evidence was found in fossilized burrows in Australia. When investigating these locations, the team noticed tiny oval impressions and, using a three-dimensional laser scanner, discovered the regular and consistent shape of a cylindrical body with distinct head and tail, as well as slightly striated musculature.
The animal varies between 2 and 7 millimeters in length and 1 to 2.5 millimeters in width. “This is the oldest fossil we have with this type of complexity,” says researcher Mary Droser.
Evolutionary biologists who study the genetics of modern animals have previously predicted that the oldest ancestor of all bilaterians would be simple, small and with rudimentary sensory organs, just like what was found. “It is really exciting that what we found is in line with their prediction,” adds Droser.
Despite its simplicity, Ikaria is complex compared to other fossils from that period. He dug thin layers of sand at the bottom of the ocean in search of organic matter, indicating sensory abilities. The burrows also preserve crossed v-shaped ridges, suggesting that the animal moved by contracting the body’s muscles. In addition, the evidence reveals that he probably had a mouth, anus and intestine.
The development of bilateral symmetry was a critical step in the evolution of animal life, giving organisms the ability to move purposefully and also to organize their bodies. Thus, a multitude of animals, such as humans and even dinosaurs, are organized around this same bilateral body plan.