"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 time of research and a first author.
While many studies have analyzed signs of early life in ancient rocks, this new paper, published in Nature Reviews Microbiology, integrates these findings with genomic data of modern organisms and recent discoveries about the early Earth's changing oceans, atmosphere, and continents.
The research highlights how early microbial life, including oxygen-producing bacteria and methane-generating archaea, influenced and adapted to shifts in Earth's oceans, continents, and 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."
The paper, a collaborative effort among experts in biology, geology, geochemistry, and genomics, traces the progression of Earth's early life forms from their initial appearance to their ecological dominance. As these microbes proliferated, they began to significantly impact their environment, notably through oxygen production via photosynthesis.
According to Tino, who is now a postdoctoral associate at the University of Calgary, the findings across each field often "agree in remarkable ways."
The study details how microbial life utilized, altered, and dispersed essential nutrients like nitrogen, iron, manganese, sulfur, and methane across the Earth. These biological pathways evolved in tandem with the planet's dramatic surface changes, sometimes driven by the microbes themselves. As continents emerged, the sun grew brighter, and oxygen levels increased, these pathways offer insights into the timelines and ecological impacts of early life forms.
Ancient rocks, often devoid of visible fossils, require chemical analysis and genomic comparisons with modern organisms to reconstruct early life. This comprehensive approach has provided a clearer picture of Earth's initial microbial influences.
"In essence, we are describing Earth's first flirtations with microbes capable of changing the global environment," said Lyons, who is also the director of the Alternative Earths Astrobiology Center in the 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 research challenges the assumption that life quickly proliferated once it appeared on Earth. By synthesizing decades of multidisciplinary studies, Lyons, Tino, and their colleagues have demonstrated that the journey from existence to ecological dominance often spanned 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.
Ultimately, the study addresses the fundamental question of our origins. However, the insights gained also have practical applications, offering clues on how life and environments might respond to climate change both now and in the future.
Additionally, the findings could guide the search for life on other planets. "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 from the Massachusetts Institute of Technology, Rika E. Anderson from the University of Washington and Carleton College, William D. Leavitt from Dartmouth College, Kurt O. Konhauser from the University of Alberta, and Eva E. Stueken from the University of Washington and University of St. Andrews.
Research Report:Co-evolution of early Earth environments and microbial life
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