Scientists have discovered how they lived the first multicellular organisms of the Earth

CC BY-SA 3.0 / Matteo De Stefano/ MUSE / Parvancorina mpsamplesubmissionScientists have discovered how they lived the first multicellular organisms of the EarthCC BY-SA 3.0 / Matteo De Stefano/ MUSE / Parvancorina minchami

. The first multicellular creatures on our planet was not like a hydras, sea sponge or other immobile invertebrates and trilobites and other moving creatures out hunting for food alone, according to a paper published in the journal Biology Letters.

«Paleontologists have long been accustomed to work with fossils that seem very strange to biologists working with living organisms. But if we sink to the bottom in the history of life on Earth, then the fossils become even more bizarre. They have no tail, legs, bones, eyes or any other features that would help to know which branch of the «tree of life» belonged to their owners, making our work very difficult,» explains Simon Darroch (Simon Darroh), a paleontologist at Vanderbilt University.

Scientists now believe that life could appear on Earth three billion years ago, but the first 2.5 billion years of its existence it spent exclusively in the unicellular form. The first multicellular creatures supposedly appeared only 600-650 million years ago, during the ediacaran period, about their lives, thanks to the almost complete absence of their remains, we know almost nothing.

Initially, scientists believed, based on the few fossils from this period that the most ancient and primitive animals of that time, the so-called rangeomorph, led a sedentary lifestyle and were similar to modern sponges. Recently, paleontologists began to doubt it, as the extraordinary nature of the reproduction of rangeomorphs require the ability for independent movement.

Darroch and his colleagues came to similar conclusions a very unusual way, having considered the «hydrodynamic» features one of the most unusual ediacaran creatures, primitive proto-arthropods Parvancorina whose remains were found in the Arkhangelsk region and in Australia.

These creatures are characterized by their unusual appearance – they look like a bent letter T, a microscopic anchor or bow and arrow, and generally resemble trilobites and other primitive inhabitants of the sea of time the Cambrian and other late historic eras. Facets of this «letter» or «anchor» was noticeably thicker compared to the rest of the body the creatures, and scientists assumed that it was attached to folds in which Parvancorina «fished» plankton from sea water.

The resemblance of this creature with the trilobites and sedentary way of life, as says Darroch already caused controversy among scientists. Many skeptics pointed to the fact that the colonies Parvancorina grew up in the «wrong» direction, attaching their «anchors» in the wrong direction, which through them had to pass water along with the tides.

The authors tested this assertion by creating a three-dimensional computer models of several specimens of Parvancorina, markedly different to its appearance and size, and having considered how their body will interact with the water.

As shown by these calculations, the anatomy of the bodies of these prehistoric «anchors» was absolutely not adapted for a sedentary lifestyle, as it did not always redirect the flow of water to the places where the alleged filtering organs of these invertebrates. In other words, if the nature of the flow has varied, then the colony Parvancorina would be completely deprived of food and died of starvation.

Accordingly, it suggests two possible things – Parvancorina could be either free-swimming organisms able to find and catch prey, or they could turn themselves or even crawl on the bottom, if they led a sedentary lifestyle. If this were true, then the ediacaran fauna was much more diverse and «dynamic» than we imagine it today, concludes the scientist.