Here is the ancestor of all animals


It’s a really bizarre great-great-great-great-grandfather, but that’s how nature wanted it. It is a tiny vermicello named Ikaria wariootia, just identified in a pile of Australian fossils discovered over a decade ago: it is 555 million years old and is the oldest bilateral organism, i.e. endowed with a front it’s a back, of two openings connected by a digestive tract and two symmetrical sides. And, believe it or not, it is a distant ancestor of almost all animals, including fish, amphibians, reptiles, birds and mammals. Therefore, human beings included.The discovery of his discovery was made by a team of scientists from the Smithsonian National Museum of Natural History, on the pages of Proceedings of the National Academy of Sciences: “The most important news,” he explained Scott Evans, one of the authors of the work, “is that it is the oldest bilateral organism ever found. Since human beings are also bilateral, we can say without fear that this organism is our ancestor and probably one of the first specimens from the bilateral branch on the tree of life “.

The first multicellular organisms, including for example sponges and algae, had very variable shapes. Overall, they are known as Ediacara fauna (name that derives from a hilly chain in southern Australia particularly rich in fossils of this type), and they lack the characteristics of most modern animals, including the presence of the mouth or ‘intestine.

One of the crucial steps for the evolution of animal life was the development of bilateral symmetry, by virtue of which life forms were able to move functionally and develop a “rational” organization of internal organs. Evolutionary biologists studying the genetics of modern animals have long suspected that the first ancestor of bilateral organisms would be a rather small being, with sense organs barely sketched; however, so far no one had managed to identify the fossilized remains of an organism with all these characteristics.

Here is the ancestor of all animals

The story changed when Evans and colleagues, carefully analyzing fossils discovered fifteen years earlier in Nilpena, southern Australia, noticed microscopic oval-shaped excisions. At this point, the scientists used a three-dimensional laser scanner, whose ‘eyes’ revealed the presence of tiny cylindrical bodies, about the size of a grain of rice, equipped with a’ head ‘and a’ tail distinct and grooved musculature. Or a structure compatible with the excisions found on fossils. That at this point it is reasonable to assume they were the ‘burrows’ dug by the animals. “We always knew that these animals would be very difficult to recognize,” said Evans. “It took the three-dimensional scans to find them.”

Here is the ancestor of all animals

Scientists called organisms Ikaria wariootia: the first word comes from Ikara, which in the Adnyamathanha language, spoken by the Aborigines who inhabit that region of Australia, means “meeting place”; the second derives from Wariota Creek, the name of the mountain range on which the discovery was made.

“At the moment, it is the oldest fossil with this degree of complexity that we are aware of,” says Evans. “Other organisms of the Ediacara fauna, such as i Dickinsonia, are probably older, but they do not have the same complexity and are almost certainly an ‘evolutionary dead end’. “And actually Ikaria wariootiadespite its small size, it is a fairly complex organism, able to hide under thin layers of sand in search of organic matter and to move by contracting the muscles of the body in a way similar to that used by modern worms. “Ikaria it looks exactly as expected by evolutionary biologists, “concludes the author proudly.” And it is really exciting that what we have observed is perfectly in line with theoretical predictions. “

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