A tiny fossil that represents the “missing link” between single-celled animals and more complex lifeforms like humans has been found near Loch Torridon, in the Northwest Highlands of Scotland.
The first living things on Earth were single-celled animals. And for billions of years these simple lifeforms were the sole inhabitants of Earth.
Then, around a billion years ago, multi-cellular organisms developed.
But until now, scientists had been unable to find an example of a creature that marked the turning point between these two approaches to biology.
The fossil remains of a new species, which researchers have named Bicellum brasieri , seems to be just that.
Charles Wellman, from the University of Sheffield, is one of the authors of the paper which is published in scientific journal Current Biology.
He says that the the origin of multi-cellular organisms and, later, animals are among the most important events in the history of life on Earth. “Our discovery sheds new light on both of these,” he writes.
“We have found a primitive spherical organism made up of an arrangement of two distinct cell types, the first step towards a complex multicellular structure, something which has never been described before in the fossil record."
“The discovery of this new fossil," he adds, "suggests to us that the evolution of multicellular animals had occurred at least one billion years ago and that early events prior to the evolution of animals may have occurred in freshwater like lakes rather than the ocean.”
Professor Wellman explains that B. brasieri wasn’t actually an animal, as scientists understand the term today.
“There’s a long, long way to go until you get real animals,” he told New Scientist.
"But it probably belonged to the larger group from which animals arose, he said.
“It’s telling us about the really early events in that lineage.”
The next question he and his colleagues have to answer is whether multi-cellular life evolved after the Earth’s atmosphere began to contain oxygen some 800 million years ago, or whether the oxygenation of the atmosphere happened after these complex lifeforms were already well established.
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