"This paper strives to inform the Earth sciences community where the research needs to go next," said Christopher Tino, a UCR PhD candidate during the research and a first author.

The study, published in Nature Reviews Microbiology, integrates data from ancient rock studies, genomic research of modern organisms, and recent discoveries about the early Earth's evolving chemistry. It illustrates how early microbes, such as oxygen-producing bacteria and methane-producing archaea, influenced and were influenced by changes in oceans, continents, and the atmosphere.

"The central message in all of this is that you can't view any part of the record in isolation," said Timothy Lyons, a UCR distinguished professor of biogeochemistry and co-first author. "This is one of the first times that research across these fields has been stitched together this comprehensively to uncover an overarching narrative."

Experts from biology, geology, geochemistry, and genomics contributed to the paper, detailing the progression of early life from its emergence to ecological significance. Microbes, as they proliferated, began altering their surroundings, notably through oxygen production via photosynthesis.

The findings from various fields often "agree in remarkable ways," according to Tino, who is now a postdoctoral associate at the University of Calgary.

The study tracks how microbial life processed and dispersed key nutrients like nitrogen, iron, manganese, sulfur, and methane. These biological pathways evolved alongside significant changes to Earth's surface. The emergence of continents, a brighter sun, and increased oxygen levels marked these transformations.

As new biological pathways developed, they influenced element cycles, indicating when early life appeared, how it interacted with the environment, and when it gained global ecological prominence. Although ancient rocks lack visible fossils, this study used their chemistry and genomes of living organisms to construct a detailed view of ancient life.

"In essence, we are describing Earth's first flirtations with microbes capable of changing the global environment," said Lyons, who also directs the Alternative Earths Astrobiology Center in UCR's Department of Earth and Planetary Sciences. "You need to understand the whole picture to fully grasp the who, what, when, and where as microbes graduated from mere existence to having a significant effect on the environment."

The study challenges the assumption that life quickly became prolific once it appeared on Earth. Only by synthesizing decades of interdisciplinary research, as Lyons, Tino, and their colleagues did, can scientists distinguish between the presence and dominance of certain microbes. The rise to ecological prominence often took hundreds of millions of years.

"Microbes that at first eked out an existence in narrow niches would later have their turn to be the big kids on the block," said Lyons.

This research addresses fundamental questions about our origins and has practical implications, such as predicting how life and environments might respond to climate change.

The findings could also support the search for extraterrestrial life. "If we are ever going to find evidence for life beyond Earth, it will very likely be based on the processes and products of microorganisms, such as methane and O2," said Tino.

"We are motivated by serving NASA in its mission," Lyons noted, "specifically to help understand how exoplanets could sustain life."

Lyons and Tino collaborated with Gregory P. Fournier of MIT, Rika E. Anderson of the University of Washington and Carleton College, William D. Leavitt of Dartmouth College, Kurt O. Konhauser of the University of Alberta, and Eva E. Stueken of the University of Washington and University of St. Andrews.

Research Report:Co-evolution of early Earth environments and microbial life

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