How a weak magnetic pulse triggered evolution 600 million years ago

Research suggests that the unusual state of Earth’s magnetic field during the Ediacaran period could have significantly influenced the development of complex life by altering the oxygen level in the atmosphere. The research shows that this period had the weakest magnetic field ever recorded, which may have increased oxygenation, allowing for larger and more active life forms. This improved understanding of geomagnetic and evolutionary dynamics provides insight into the life potential on other planets. Credit: SciTechDaily.com

There is evidence that a weak magnetic field may have fueled the proliferation of life millions of years ago.

The Ediacaran Period, which lasted about 635 to 541 million years ago, was a pivotal time in Earth’s history. It marked a transformative era in which complex, multicellular organisms emerged, setting the stage for the explosion of life.

But how did this wave of life proceed and what factors on Earth may have contributed to it?

Researchers from the University of Rochester have found compelling evidence that Earth’s magnetic field was in a highly unusual state as the macroscopic animals of the Ediacaran period diversified and flourished. Their study, published in Nature Communication Earth & Environmentraises the question of whether these fluctuations in Earth’s ancient magnetic field led to shifts in oxygen levels that could have been crucial to the proliferation of life forms millions of years ago.

Researchers at the University of Rochester studied Earth’s magnetic field during the transformative Ediacaran period, which spanned from about 635 to 541 million years ago. The research raises questions about factors that may have fueled the emergence of complex, multicellular organisms such as the Ediacaran fauna, notable for their similarity to early animals. Credit: University of Rochester Illustration / Michael Osadciw

According to John Tarduno, the William Kenan, Jr. professor in the Department of Earth and Environmental Sciences, one of the most remarkable life forms during the Ediacaran period was the Ediacaran fauna. They were notable for their similarity to early animals; some even grew to over a meter in size and were mobile, indicating that they likely required more oxygen compared to earlier life forms.

“Previous ideas for the appearance of the spectacular Ediacaran fauna included genetic or ecological driving factors, but the close timing with the ultra-low geomagnetic field motivated us to reconsider environmental issues, and in particular the oxygenation of the atmosphere and the ocean,” says Tarduno. , who is also dean of research for the School of Arts & Sciences and the School of Engineering and Applied Sciences.

The Magnetic Mysteries of Earth

About 2,000 miles below us, liquid iron spins in Earth’s outer core, creating the planet’s protective magnetic field. Although invisible, the magnetic field is essential for life on Earth because it protects the planet from solar wind – radiation currents from the sun. But Earth’s magnetic field was not always as strong as it is today.

Researchers have proposed that an unusually low magnetic field may have contributed to the rise of animal life. However, it has been challenging to investigate the connection due to limited data on the strength of the magnetic field during this period.

Fossil impression of Dickinsonia, an example of the Ediacaran fauna, found in present-day Australia. Credit: Shuhai Xiao, Virginia Tech

Tarduno and his team used innovative strategies and techniques to investigate the strength of the magnetic field by studying the magnetism trapped in ancient feldspar and pyroxene crystals from anorthosite rock. The crystals contain magnetic particles that maintain magnetization from the moment the minerals were formed. By dating the rocks, researchers can construct a timeline of the development of Earth’s magnetic field.

By using advanced tools, including a CO₂ laser and the laboratory’s superconducting quantum interference device (SQUID) magnetometer, the team precisely analyzed the crystals and the magnetism trapped within them.

A weak magnetic field

Their data show that Earth’s magnetic field during the Ediacaran period was at times the weakest field yet known – up to 30 times weaker than the current magnetic field – and that the ultralow field strength persisted for at least 26 million years.

A weak magnetic field makes it easier for charged particles from the sun to remove lightweight atoms, such as hydrogen, from the atmosphere, causing them to escape into space. If hydrogen loss is significant, more oxygen may remain in the atmosphere instead of reacting with hydrogen to form water vapor. These reactions can lead to a build-up of oxygen over time.

Fossil impression of Fractofusus, an example of the Ediacaran fauna, found in what is now Newfoundland, with a Canadian cent nearby for its scale. Credit: Shuhai Xiao, Virginia Tech

Tarduno and his team’s research suggests that the ultraweak magnetic field during the Ediacaran period caused a loss of hydrogen for at least tens of millions of years. This loss may have led to increased oxygenation of the atmosphere and surface ocean, allowing more advanced life forms to emerge.

Tarduno and his research team previously found that the geomagnetic field recovered in strength during the subsequent Cambrian period, when most animal groups appeared in the fossil record and the protective magnetic field was restored, allowing life to thrive.

“If the extremely weak field had remained after the Ediacaran, Earth could have looked very different from the water-rich planet it is today: water loss could have gradually dried up the Earth,” Tarduno says.

Core dynamics and evolution

The work suggests that understanding planetary interiors is crucial when thinking about the potential for life beyond Earth.

“It’s fascinating to think that processes in the Earth’s core could ultimately be linked to evolution,” says Tarduno. “As we consider the possibility of life elsewhere, we must also consider how the insides of planets form and develop.”

For more information about this research, see How Earth’s Weak Magnetic Field Facilitated the Emergence of Complex Life.

Reference: “Near Collapse of the Geomagnetic Field May Have Contributed to Atmospheric Oxygenation and Animal Radiation in the Ediacaran Period” by Wentao Huang, John A. Tarduno, Tinghong Zhou, Mauricio Ibañez-Mejia, Laércio Dal Olmo-Barbosa, Edinei Koester , Eric G. Blackman, Aleksey V. Smirnov, Gabriel Ahrendt, Rory D. Cottrell, Kenneth P. Kodama, Richard K. Bono, David G. Sibeck, Yong-Xiang Li, Francis Nimmo, Shuhai Xiao and Michael K. Watkeys, May 2, 2024, Communication Earth & Environment.
DOI: 10.1038/s43247-024-01360-4

This research was supported by the US National Science Foundation.