Rewritten Title: New Study Reveals Fungi as Pioneers of Terrestrial Life, Long Before Plants
Rewritten Article:
A groundbreaking study published in Nature Ecology & Evolution is reshaping our understanding of life’s history on Earth, revealing that fungi were among the planet’s first major evolutionary pioneers, diversifying hundreds of millions of years before land plants emerged. This research, conducted by the Okinawa Institute of Science and Technology (OIST) in collaboration with international scientists, positions fungi as foundational architects of the earliest terrestrial ecosystems.
The Five Paths to Complex Life
Professor Gergely Szöllősi, a co-author of the study and head of the Model-based Evolutionary Genomics Unit at OIST, provides a broader context for this discovery.
“Complex multicellular life—organisms composed of cells with specialized roles working in cooperation—evolved independently in five major groups: animals, land plants, fungi, red algae, and brown algae,” he stated. “On a planet once dominated by single-celled organisms, this revolutionary development occurred not once, but at least five separate times. Understanding when these groups emerged is crucial for reconstructing the history of life on Earth.”
This leap to multicellularity was more than just cells clustering together; it marked the dawn of true organisms with specialized cells organized into tissues and organs. This transformation required sophisticated molecular systems for cell adhesion and complex communication networks to coordinate functions—innovations that arose independently in all five lineages.
Fossil Clues and the Fungal Mystery
For most of these groups, fossils act as a geological calendar, providing anchor points in Earth’s deep history. For instance:
- Red algae likely appeared around 1.6 billion years ago.
- Animals emerged around 600 million years ago.
- Land plants diversified approximately 470 million years ago.
However, fungi have long been an enigma for paleontologists. Their soft, filamentous bodies rarely fossilize well. Furthermore, unlike animals and plants, which have a single origin for multicellularity, fungi acquired this trait multiple times from different single-celled ancestors, making it difficult to pinpoint their precise origins.
Decoding the Molecular Clock
To fill the gaps in the fungal fossil record, scientists turned to the “molecular clock”—a concept that estimates the relative time of species divergence based on the relatively constant rate of genetic mutations over generations.
But without calibration, this clock only shows relative time. To determine an exact timeline, it must be anchored with fossil evidence—a task that has been persistently challenging for fungi. The OIST team overcame this by using an innovative calibration source: Horizontal Gene Transfer (HGT), the rare transfer of genetic material between different fungal species.
Genes That Leap Through Time
“While genes are typically transferred vertically from parent to offspring, HGT is like a genetic side-hop from one species to another,” explained Professor Szöllősi. “These events provide powerful temporal clues. If a gene was transferred from lineage A to lineage B, it is clear that the ancestors of A must be older than the descendants of B.”
By identifying 17 such transfer events, the researchers established a series of “older/younger” relationships that, combined with scarce fossil data, allowed for a more precise calibration of the fungal timeline.
A Revised Timeline for a Biological Pioneer
The team’s analysis concludes that the common ancestor of all modern fungi lived between 1.4 and 0.9 billion years ago—far earlier than the rise of land plants. This revised timeline underscores the profound and ancient role of fungi, suggesting their long-term interactions with algae were instrumental in paving the way for all subsequent terrestrial life.