Spanning from about 635 to 541 million years ago, the Ediacaran Period was a pivotal time in the Earth's history. It marked a transformative era during which complex, multicellular organisms emerged, setting the stage for the explosion of life that followed.
Now, scientists believe that this could all be down to an unusually low magnetic field that could have led to a crucial shift in oxygen levels.
Research from the University of Rochester has shown that during the Ediacaran Period the Earth's magnetic field reached its weakest levels known to date – up to 30 times weaker than the magnetic field today.
This ultra-low field strength – which lasted for at least 26 million years – led to a build-up of oxygen in the atmosphere and the surface of the ocean, and a lowering of hydrogen. Together, these factors created conditions that made it easier for more advanced life forms to emerge.
What is the magnetic field?
About 1,800 miles below us, liquid iron churns in Earth's outer core, creating the planet's protective magnetic field. Though invisible, the magnetic field is essential for life on Earth because it shields the planet from solar wind -- streams of radiation from the sun.
According to John Tarduno from the Department of Earth and Environmental Sciences at the University of Rochester, one of the most remarkable life forms that developed during the Ediacaran Period was the Ediacaran fauna - a plant-like creature and earth's first animal - and the increase of oxygen could have helped them.
Ediacaran fauna were notable for their resemblance to early animals – some even reached more than a metre in size and were mobile, indicating they probably needed more oxygen compared to earlier life forms.
"Previous ideas for the appearance of the spectacular Ediacaran fauna have included genetic or ecologic driving factors, but the close timing with the ultra-low geomagnetic field motivated us to revisit environmental issues, and, in particular, atmospheric and ocean oxygenation," says Tarduno.
The weak magnetic for triggered life because of the increase in oxygen, but this wasn’t sustainable for maintaining life as the reduced hydrogen meant the world's water would have dried up. The magnetic field was also needed for protection.
Therefore when the magnetic field recovered its strength during the subsequent Cambrian Period and the protective magnetic field was reestablished more animal groups begin to appear in the fossil record, and life was able to thrive.
"If the extraordinarily weak field had remained after the Ediacaran, Earth might look very different from the water-rich planet it is today: water loss might have gradually dried Earth," Tarduno says.
"It's fascinating to think that processes in Earth's core could be linked ultimately to evolution," Tarduno says. "As we think about the possibility of life elsewhere, we also need to consider how the interiors of planets form and develop."
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The study was published in Nature Communications Earth & Environment
This research was supported by the US National Science Foundation.
Main image: Dickinsonia, an extinct animal, that lived during the late Ediacaran period © Getty Images