Earth's Magnetic Field 'Near-Collapse' Boosted Evolution, Scientists Think

Life on Earth may exist thanks to a brief faltering in our planet's protective magnetic field shell, scientists have found.

A bizarre drop in the strength of the magnetic field has been found to have occurred between 591 and 565 million years ago, which coincides with a major increase in the oxygen levels in Earth's atmosphere and ocean, according to a new paper in the journal Communications Earth & Environment.

This increase in oxygen is associated with the evolution of some of the earliest species of complex life on our planet, which therefore may have resulted from the magnetic field's weakening.

Life first evolved on Earth around 3.7 billion years ago, existing as only very simple single-celled organisms for billions more years until multicellular life evolved about 1.7 billion years ago. Animals only appeared around 580 million years ago, in the Ediacaran period, and were mostly soft-bodied jellyfish-like creatures. However, between 575 and 565 million years ago, animals began to diversify in complexity, which is thought to have been triggered by a sudden jump in the level of oxygen in the atmosphere and oceans.

"Oxygen has long been identified as a key 'environmental gatekeeper,' allowing for evolutionary innovation and for meeting the energy demands of animals," researchers wrote in the paper.

"Although sponges and microscopic animals can survive at low levels of dissolved oxygen (as low as around 1.5 μM, equivalent to 0.5 percent present atmospheric level [PAL]), macroscopic, morphologically complex, and mobile animals require a greater amount of oxygen to support their metabolic demands," the researchers wrote. "A complex animal ecosystem involving long food chains and predators requires still greater amounts of oxygen."

"Multiple lines of geochemical evidence point to a possible increase in atmospheric and oceanic O2 levels in the late Ediacaran Period, specifically in the period of around 575–565 Ma," they said.

However, the reasons for this spike in oxygen were unknown—until now.

In the paper, the team of international researchers revealed that they analyzed the magnetic properties of 21 plagioclase crystals—a common mineral in the crust of our planet—extracted from a rock formation in Brazil dating back 591 million years. They discovered that when the crystals were formed, the Earth's magnetic field was weaker than had ever been seen before, at about 30 times less strong than it currently is.

Other crystals found that formed around 2,000 million years ago showed that the magnetic field was around the same strength as it is today, meaning that the field weakened and then strengthened again.

After examining previous data, the researchers discovered that this weak magnetic field lasted around 26 million years, between around 591 and 565 million years ago. They suggest that this period of weakened magnetic field could have sparked the evolution of more complex life by allowing more hydrogen to escape from our atmosphere and increasing the concentration of oxygen.

"This concurrence raises the question of whether enhanced H ion loss in a reduced magnetic field contributed to the oxygenation, ultimately allowing diversification of macroscopic and mobile animals of the Ediacara Fauna," the researchers wrote.

This study provides "a framework for future studies quantifying hydrogen loss, oxygenation of the atmosphere and the potential consequences on the evolution of complex animals highlighted by the synchroneity of these phenomena and the near collapse of the geodynamo," the researchers said.

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