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Early animal life digging into the ocean floor was the cause of a global warming event half a billion years ago, a new study released Monday demonstrates.
It took about 100 million years for small animals that dig into the sandy seabed to breathe oxygen from the water and poison their own environment with carbon dioxide, report Nature Communications scientists. But they got there.
Life began to evolve about 4 billion years ago, despite controversial evidence of fossil bacteria in some crustal rocks. (It is thought that the Earth itself was created 4.6 billion years ago.)
The first life would have been simple cells without nuclei, which looked like bacteria today. Then complex cells with nuclei, eukaryotes, would have evolved, then multi-cellular, plant and animal life.
When all these things happened, it was fiercely debated: the fossils suspected to be multicellular fungi found in South Africa date back 2.4 billion years ago.
It can be said, however, that the true explosion of animal speciation occurred in the Cambrian, 550 million years ago. This evolutionary explosion has resulted in an extraordinary diversity of animals, arthropods with simple nervous systems, but sports eyes, legs and claws.
Scientists have long wondered what triggered this explosive explosion of Cambrian life forms. Prior to this, the ocean had been low in oxygen and the animals it contained were probably small, lethargic and probably confined to eating bacterial mats on the seafloor.
In 2016, an article by Nature proposed that the development of complex animals be facilitated by the oxygenation of the oceans. Primitive algae absorbed carbon dioxide and produced oxygen. The primordial animals living in the mud of the seafloor could breathe more easily, literally, and had the metabolic luxury of evolving advanced features such as legs and predatory habits – which in turn would have triggered an evolutionary arms race.
Some of the Cambrian animals were not small: the dreaded Anomalocaris canadensis for example could be a formidable 60 centimeters long. And some early animals have dug.
Tunnel of Hell
But to the consternation of the Cambrian animals that collide, this luxurious oxygenation will not last, report Sebastiaan van de Velde of the Vrije Universiteit of Brussels and colleagues of the universities of Exeter, Leeds and Antwerp in their new newspaper . They suspect that it was the fault of the burrowers.
While animals freaked in the oceans and ate bacterial mats and algae, they breathed oxygen and exhaled carbon dioxide just like us. And the concentration of carbon dioxide in the air has increased and increased, just like our emissions.
Jenny
About 100 million years ago, scientists write, these primordial animals have gradually ruined their own environment. "Oxygen levels in the ocean have fallen and carbon dioxide has caused global warming," they summarize.
Why would they think the burrowers are dunnit? "Like worms in a garden, tiny creatures on the seabed disrupt, mix and recycle dead organic matter – a process known as bioturbation," says Professor Tim Lenton, of the University of Toronto. ; Exeter. If they "bioturb" the entire bottom of the ocean, you get a critical mbad.
Apparently, there was at that time a critical mbad of animals burrowing. Professor Filip Meysman of the University of Antwerp confirms that a decrease in ocean oxygen levels occurred about 520 million years ago; and points of geological evidence at rising CO levels 2 .
"We knew that the warming was occurring at this stage of the Earth's history, but we had not realized that it could be driven by animals," said Dr. Benjamin Mills of the University of Leeds.
Increases in temperatures driven by carbon dioxide on Earth may have underpinned the multiple mbad extinctions that followed the Cambrian explosion, and the parallel is evident. Although what it took to worms 100 million years ago, humans have reached 100, and we have done it more dramatically. Scientists are horrified to find that carbon dioxide concentrations in the atmosphere (and water) have never increased as rapidly as over the past 200 years. But just like our predecessors on the planet, we poison it for ourselves and for all others, and like them, we can end up because of it.
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