A theory puts life on land 65 million years early

Dickinsonia costata, a typical fossil of the Ediacara biota
Dickinsonia costata, a typical fossil of the Ediacara biota

An article published in the journal “Nature” in December is causing discussions among paleontologists. The reason is that according to Gregory Retallack, a geologist at the University of Oregon in Eugene, life on land began 65 million years earlier than is generally estimated.

The research carried out by Gregory Retallack concers Ediacara fossils, which date back to a period ranging from about 635 to 542 million years ago and have always been the center of controversy in the field of paleontology. The first organisms belonging to the Ediacaran biota were found in 1868 but only after many years researchers started realizing their importance.

At the time, the study of fossils was still in a primitive stage and there were religious reasons that hindered it. In the first half of the twentieth century, the situation improved and not accidentally an important finding for the research on these ancient fossils occurred in the Ediacara Hills, Australia, in 1946.

Despite these findings, scientists kept on believing that these fossils were dated to the Cambrian and that before it there were no life forms. It was only after another decade that new discoveries and geological analyzes convinced paleontologists that the Ediacara biota dated back to the pre-Cambrian. The term Ediacaran gradually started being used to indicate the geological period that ranges from 635 to 542 million years ago, although only in 2004 it was officially ratified by the International Union of Geological Sciences (IUGS).

Over the years, many other fossil belonging to the Ediacara biota have been found almost all over the world. These creatures belong to certain morphological plans but their classification is in dispute. They’re generally considered to belong to the animal kingdom and are considered among the earliest forms of sea complex life. Instead, Gregory Retallack believes that the Ediacara territories were dry land full of lichens.

Gregory Retallack argues that the most famous genera of Ediacara biota such as the Dickinsonia (photo ©Verisimilus) and Spriggina are not animals but lichens and their traces actually include slime moulds and soil structures. Retallack proposed this theory for the first time in the ’90s, in this new research he brings new geological data in support of his thesis such as the color red and the erosion patterns, which according to him were formed in a terrestrial environment and not a marine one.

According to the majority of paleontologists, the Nature article adds nothing new to Gregory Retallack’s theory. According to the many skeptics, what are considered evidence that those organisms were lichens that lived on land have alternative explanations compatible with their classification among marine animals.

A minority of scientists supports Gregory Retallack’s theory so the debate continues. Those are very ancient fossils so their study isn’t easy and at any time new ones can be found with other characteristics that contradict current ideas. Science works this way, with the possibility that new information will lead to changes even radical in the existing theories, we’ll see if this is the case.

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