Life’s explosive diversification unleashed a chemical revolution in earth’s crust

Around 500 million years ago, there was a rapid diversification of life in the oceans. In a relatively short period of time, simple, soft-bodied creatures evolved into complex multicellular organisms with shells and skeletons. However, new research led by the University of Cambridge suggests that this explosion of life also had a significant impact on the chemistry of Earth’s crust.

The study, published in the journal Science Advances, reveals that following the Cambrian explosion, the amount of phosphorus, a vital nutrient for life, in crustal rocks tripled. This increase in phosphorus played a crucial role in supporting the continued expansion of life on our planet.

By analyzing a comprehensive database of information on ancient rocks from around the world, the researchers created a map illustrating how the chemistry of Earth’s crust has changed over the past 3 billion years. They discovered that phosphorus levels in crustal rocks have steadily increased since the Cambrian explosion, up to the present day.

Lead author Craig Walton from Cambridge’s Department of Earth Sciences explains, “We found that ancient life had a profound impact on its environment—even to the point of resetting the chemistry of the continental crust.”

Co-author Oliver Shorttle, who is affiliated with both Cambridge’s Department of Earth Sciences and the Institute of Astronomy, adds, “This shows how the development of life can influence the growth of further life, and in turn, how much life a planet can go on to support.”

Phosphorus is one of the six essential elements for life, alongside carbon, hydrogen, nitrogen, and sulfur. While these elements are universally required by all forms of life, phosphorus is particularly important and can be challenging to access since it is typically locked up in minerals within Earth’s crust.

This research highlights the interconnectedness between life and the planet’s geological processes. It demonstrates how the evolution and expansion of life forms can shape and alter the composition of Earth’s crust, ultimately influencing the conditions for the sustenance of life on a planetary scale.

Shorttle explains that phosphorus is believed to be one of the limiting factors for life in the oceans. Unlike carbon and nitrogen, which are present in the atmosphere, phosphorus needs to be extracted from rocks before it can be utilized by living organisms. The process begins with the weathering of rocks through interactions with rainwater, which releases phosphate that is then carried by rivers into the oceans. Within the oceans, organisms such as plankton and eukaryotic algae metabolize phosphorus, and these organisms are consumed by larger animals in the food chain.

When these organisms die, much of the phosphorus is returned to the oceans, undergoing an efficient recycling process. This recycling process plays a critical role in controlling the overall amount of phosphorus in the ocean, which is essential for supporting life. Walton emphasizes the significance of understanding when this process began, as it is responsible for sustaining the life we observe today.

The researchers propose that an increase in oxygen during the Cambrian explosion could explain the rise in phosphorus levels in rocks. The availability of more oxygen at that time may have facilitated the breakdown of deep-sea biomass by oxygen-fueled bacteria, leading to the recycling of phosphorus in shallow coastal regions. As a result, phosphorus was transported back to the land and better preserved in the rocks forming the continents. Walton suggests that these changes played a crucial role in fueling the emergence of complex life forms.

However, the exact sequence of events and the interplay between oxygen, phosphorus, and the evolution of complex life forms remain a topic of debate. The researchers are now focusing on further investigating the timing and trigger of this phosphorus enrichment in the Earth’s crust to gain a more detailed understanding of these processes.

Source: University of Cambridge

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