Ancient Fungi: Earth's Earliest Decomposers

5. Ancient Fungi and the Great Oxidation Event: A Symbiotic Revolution

One of the most intriguing chapters in Earth's history is the interaction between ancient fungus and the Great Oxidation Event (GOE). About 2.4 billion years ago, this crucial epoch saw a significant rise in atmospheric oxygen levels, therefore changing the chemistry of the planet and opening the path for the creation of sophisticated life forms. Although photosynthetic cyanobacteria were the main drivers of the GOE, new data points point to ancient fungus as being absolutely vital, if indirectly, in this transforming event. Early fungi and rudimentary photosynthetic organisms may have created symbiotic interactions that increase oxygen generation, therefore influencing the drastic change in the atmosphere of Earth One hypothesis holds that by means of their breakdown activities, fungus produced nutrients that drove the expansion of cyanobacteria producing oxygen. Fungi produced necessary elements like phosphorous more readily in the environment by breaking down organic matter and weathering rocks. This nutrient enrichment might have caused algal blooms and more cyanobacterial activity, hence accelerating the oxygen generation. Moreover, the development of fungal-plant symbioses—especially mycorrhizal relationships—may have indirectly helped the atmosphere to oxygenate itself. Early terrestrial plants were able to flourish and expand thanks to these alliances, hence raising the world biomass of photosynthetic species. These plants helped the atmosphere gradually accumulate oxygen by photosynthesis, hence generating oxygen. In the framework of the GOE, the function of fungus in soil creation was also rather important. Fungi enabled the spread of terrestrial plants as they helped produce more complex and nutrient-dense soils. This extension of terrestrial vegetation would have raised oxygen generation even further, therefore helping to continuously oxygenize the atmosphere. Fascinatingly, the increase in atmospheric oxygen levels might have shaped fungus development. More effective metabolic pathways developed in fungus most likely driven by the availability of oxygen, enabling them to exploit fresh ecological niches and diversify more. Recent research also implies that some ancient fungus might have been able to use oxygen in their metabolic activities, therefore enabling aerobic respiration. If this is the case, part of the extra oxygen generated during the GOE would have been consumed by these fungus, therefore helping to control oxygen levels and stop them from reaching dangerous quantities.