In a groundbreaking study published in the prestigious journal Science, researchers from the HUN-REN Center of Ecological Research (HUN-REN CER) in Hungary have joined an international team to unravel a remarkable mystery about the origins of bacterial life on Earth. Their findings suggest that some forms of bacteria developed the ability to utilize oxygen nearly a billion years before the Earth’s atmosphere became rich in it, fundamentally altering long-held beliefs about microbial evolution and the Great Oxidation Event.
Setting the Stage: The Great Oxidation Event
A Turning Point in Earth’s Atmospheric History
Roughly 2.33 billion years ago, Earth experienced a pivotal shift known as the Great Oxidation Event (GOE). This event marked the first significant rise of oxygen in the planet’s atmosphere, a change widely attributed to the photosynthetic activity of cyanobacteria. Prior to this, Earth’s environment was mostly anoxic, meaning it lacked oxygen.
READ MORE: Surprise Discovery: ‘Hairy’ Medieval Books Bound in Sealskin
The GOE was instrumental in reshaping Earth’s biosphere and paving the way for more complex life forms. It has long been assumed that the ability of organisms to use oxygen, known as aerobic respiration, developed only after oxygen levels in the atmosphere rose. However, the latest research indicates that this ability may have evolved much earlier than previously believed.
New Analytical Methods Reveal Ancient Clues
Combining Fossil, Genetic, and Geological Data
Due to the absence of fossil evidence for most bacteria, studying the evolutionary timeline of microbes has always been challenging. To overcome this, the international research team employed a unique combination of genetic reconstruction, geological benchmarks, and advanced computational methods.
Using machine learning (ML) algorithms, the scientists identified bacteria capable of aerobic respiration. They then applied Bayesian statistical analysis to determine the likely timelines for when these bacteria first appeared. Importantly, their models assumed that the aerobic bacteria evolved after the GOE—but what they found challenged this assumption.
Stunning Findings: Oxygen Use Preceded Atmospheric Oxygen
Bacteria Were Breathing Oxygen Long Before It Filled the Air
The study analyzed 1,007 bacterial genomes and identified 84 independent evolutionary events where bacteria transitioned from anaerobic (oxygen-free) to aerobic (oxygen-using) life. While the majority of these events occurred after the GOE, the researchers found at least three clear instances where bacteria developed aerobic capabilities hundreds of millions of years earlier.
The earliest of these transitions predated the GOE by nearly 900 million years—an astonishing revelation. This implies that localized pockets of oxygen, perhaps in the form of trace amounts produced by non-photosynthetic mechanisms or photochemical reactions, may have been present long before oxygen became abundant in the atmosphere.
Rewriting the Evolutionary Timeline
Implications for the Origin of Life and Photosynthesis
One of the most striking aspects of this research is its potential to reshape our understanding of not just respiration but the entire timeline of life on Earth. The study proposes that the ability to utilize oxygen may have preceded—and possibly even facilitated—the evolution of photosynthesis itself.
It has traditionally been thought that photosynthetic organisms evolved first and created oxygen-rich environments, enabling the evolution of aerobic respiration. But the reverse may also be true: that aerobic metabolic pathways laid the groundwork for the genetic developments that made oxygen-producing photosynthesis possible.
Tracing Life Back to the Earliest Earth
When Did the First Bacteria Emerge?
The researchers were also able to estimate when the last universal common ancestor of all present-day bacteria lived. Their analysis places this ancestor between 4.4 and 3.9 billion years ago—right at the dawn of Earth’s history, shortly after the planet cooled enough to support liquid water.
Major bacterial lineages emerged later, between 2.5 and 1.8 billion years ago, coinciding with major shifts in Earth’s environment and climate. Remarkably, many modern bacterial families, including those that play roles in human health and environmental processes today, only arose 750 to 600 million years ago—alongside the first animals and plants.
Innovation in Methodology: A Blueprint for Future Research
A New Way to Study Ancient Microbes Without Fossils
To make these determinations, the team developed a new analytical approach that integrates genetic data with fossil records and geochemical indicators. This method offers a powerful way to study microorganisms that left no fossil trace, which includes the vast majority of microbial life.
According to the researchers, this multi-disciplinary approach opens new doors for studying other microbial species and even viruses, allowing scientists to investigate the early biochemical capabilities and environmental adaptations of Earth’s oldest life forms.
International Collaboration and Hungarian Excellence
HUN-REN CER Plays a Pivotal Role in Global Breakthrough
The HUN-REN Center of Ecological Research (CER) has been at the forefront of microbial and evolutionary biology research in Hungary. Their participation in this international collaboration exemplifies the country’s growing contribution to major global scientific endeavors.
The study not only enhances the reputation of Hungarian research institutions but also reinforces the importance of global cooperation in tackling the biggest questions about our origins and evolution.
Future Applications: Searching for Life on Other Planets
Could This Research Help in the Search for Extraterrestrial Life?
The implications of this research extend beyond Earth. Understanding how life adapted to oxygen in low-oxygen environments can inform the search for life on other planets. For example, if life exists or existed on Mars or Europa, it may have evolved under similar conditions, where oxygen is present only in trace amounts.
These findings underscore the adaptability of life and suggest that microbial life may be more versatile and widespread than previously imagined—both on Earth and potentially elsewhere in the universe.
Conclusion: Breathing New Life into an Ancient Mystery
This surprising discovery redefines our understanding of microbial evolution and the deep history of life on Earth. The revelation that bacteria were using oxygen nearly a billion years before it saturated the atmosphere not only shifts key timelines but also raises fascinating questions about how life begins, evolves, and adapts to its environment.
By developing a powerful new approach to study life’s earliest adaptations, scientists from HUN-REN CER and their collaborators have opened up exciting new frontiers in biology, astrobiology, and evolutionary science.
As this research continues, one thing is clear: even after billions of years, Earth’s oldest organisms still have stories left to tell.
