For four billion years, the world's oceans have been the domain of single-celled microbes. But suddenly that changed and all kinds of strange new life forms appeared. Australian researchers have finally discovered the cause of this crucial moment in evolution.
They have succeeded in very accurately dating some of the oldest fossils of complex, multicellular life – the so-called Ediacaran organisms. For this unique discovery, the researchers used successive layers of volcanic rocks as bookmarks in the book on the geological history of our planet, as it appears poetic.
Volcanic time capsule
Researcher Anthony Clark Tells how they worked. “The Coed Cohion quarry in Wales contains an abundance of fossils of shallow marine life from ancient times. We used the eruption of an ancient volcano, which covered the animals in dust and lava, as a time marker. “We succeeded in dating the age of the fossils to 565 million years, with an accuracy of To 0.1 percent.’” Similar Ediacaran fossils have also been found in the ground elsewhere in the world. We can now say with a great deal of certainty that they were part of a very ancient group of animal species that evolved in the world's oceans as the Earth slowly thawed after a long ice age.
The Ediacaran organisms seemed very distinctive. “These creatures were similar in some ways to modern marine species, such as jellyfish. But they were very strange creatures. Some were fern-like, others were shaped like cabbages or sea feathers,” the British geologist said.
The name of the fossils is easy to explain. “We can directly link fossils found on land in Wales to the famous Ediacara fossils in South Australia. The name comes from the Ediacara Hills, where the first fossils of Ediacara organisms were found. This led to the discovery of the first new geological period in more than a century », explains Australian Professor Chris Kirkland. «British fossils provide some of the oldest evidence of the extensive presence of multicellular organisms. They represent an important turning point in Earth's biological history and show that some geological processes, such as the melting of our planet after the Ice Age, are strongly linked to biology, or the transition to more complex, multicellular organisms.
The study shows how important it is to understand how ecosystems that are hundreds of millions of years old work. Only in this way can we uncover the secrets of the distant past of our planet and understand the evolution of life on Earth.
Life in Ediacara
The Ediacaran Period is the last period of the Neoproterozoic Era and lasted from 630 to 542 million years ago. The first indications of new, more complex life forms emerging at that time come from the Dushantou Formation in Guizhou Province in China and date back to 600 million years ago. Fossils have been found that have been interpreted as animal embryos, but it is not yet certain whether this is true. They are also seen as large sulfur bacteria.
During the Ediacaran period, the first metazoa evolved. Fossils of these multicellular organisms between 575 and 542 million years old have been found in more than forty places around the world. These animals had no exoskeleton, yet some of their fossils are remarkably well preserved. The role these organisms played in the evolution of life on Earth is not entirely clear. Some scientists suspect that they are the forerunners of life that appeared during the Cambrian explosion, but others see it as an evolutionary dead end.
More oxygen after the ice age
There was an ice age in the Ediacaran period. We know this, among other things, from deposits found in the Jaskiers Glacier, which are 580 million years old. This was before the emergence of organisms in the Ediacaran period. Therefore, the evolution of these organisms appears to be linked to the increase in oxygen concentration in the oceans after the end of the Ice Age.
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