Life on land didn’t begin with great forests; it began with small, stress-tolerant partnerships. A new study, published in the journal Science Advances, provides compelling evidence that lichens were already widespread approximately 410 million years ago during the Devonian Period, long before complex, rooted plants took hold.
The research identifies the long-enigmatic Devonian fossil, Spongiophyton, as a true lichen a symbiotic living partnership between a fungus and an alga. This discovery fundamentally repositions lichens as key pioneers in the transformation of Earth’s surface from bare rock to a habitable landscape.
Chemical Fingerprints Confirm Ancient Partnership
The breakthrough came from a detailed analysis of a fossil from southern Brazil. Lead paleobiologist Bruno Becker-Kerber at Harvard University, whose research focuses on early life on land, spearheaded the effort.
To confirm the organism’s identity, the team used a synchrotron, a high-energy X-ray source, to map the internal structures of the mummified fossil in three dimensions without destroying it.
The scans revealed a structure strikingly similar to modern lichens: a flattened body (thallus) containing branching fungal filaments (hyphae) weaving through clusters of round algal cells.
Chemical tests showed the fossil’s organic matter was rich in nitrogen compounds and alkyl-pyridines, molecules that form when chitin the tough polymer in fungal cell walls breaks down. This confirmed the presence of fungal tissue, a signature unlike typical plant or free-living algal material.
The researchers also found calcite crystals near the surface and filament walls, which likely replaced earlier calcium oxalate, a common mineral product in living lichens.
“Our findings show that lichens were not marginal organisms, but key pioneers in the transformation of Earth’s surface,” said Becker-Kerber.
Earth’s First Ecosystem Engineers
The widespread occurrence of Spongiophyton across multiple Devonian rock layers suggests lichens were ecologically prominent just as life was making the crucial shift from water to land, a process called terrestrialization.
These simple, yet hardy, communities were essential in establishing the first terrestrial ecosystems:
- Soil Creation: By releasing acids and trapping dust, lichens helped rock crumble and create the first thin layers of organic soil that more complex plants could later use.
- Nutrient Cycling: They played a vital role in unlocking nutrients from the barren surfaces.
- Climate Regulation: Today, cryptogamic covers (carpets of lichens, mosses, and algae) fix roughly seven percent of terrestrial plant production. Their Devonian ancestors would have similarly contributed to stabilizing surfaces, slowing erosion, and affecting global carbon and nutrient cycles.
The fossils likely thrived in the cold, high-latitude regions of the ancient supercontinent Gondwana (South America and Africa), which fits the resilient nature of modern lichens in harsh settings.
The study concludes that before deep roots took hold, this humble fossil partnership was already performing the foundational “quiet work” that ultimately made land livable, forever linking the story of life’s beginnings to the planet’s ongoing balance.