An international team of scientists has determined that fungi originated between 900 million and 1.4 billion years ago, predating plants and animals by hundreds of millions of years. This discovery, based on advanced molecular dating and gene transfer analysis, suggests fungi were key pioneers in Earth's early terrestrial ecosystems. The findings were published in Nature Ecology & Evolution.
Researchers, including evolutionary biologist Eduard Ocaña from the Universitat Oberta de Catalunya (UOC), analyzed fungal fossils, genomic sequences from over 100 species, and horizontal gene transfers to reconstruct the timeline. Horizontal gene transfer, where genes move between species, helped establish relative ages: "When a gene jumps from one organism to another, that tells us that the two existed at the same time," Ocaña explained.
The study pushes back fungi's origins far beyond previous estimates. "As a group, fungi are much older than previously imagined. It's highly likely that they were already around over a billion years ago, making them one of the oldest major groups of eukaryotes," Ocaña said. Fungi, which include mushrooms, molds, and yeasts, arose before animals (about 600 million years ago) and multicellular land plants (around 500 million years ago).
Evidence indicates fungi inhabited land at least 800 million years ago, interacting with ancestors of land plants resembling green algae. These early partnerships, similar to modern mycorrhizae, likely aided the transition to terrestrial life. "Our findings show that fungi were already present on land environments at least 800 million years ago and had ecological interactions with the ancestors of multicellular land plants," Ocaña noted. He added, "If we accept that fungi were instrumental in helping plants colonize the Earth, our theory is that this partnership may have started much earlier than previously thought, in environments similar to biological soil crusts or the microbial mats that we still have today."
By breaking down minerals and forming soils, ancient fungi transformed barren landscapes, challenging views of an empty early Earth. The collaborative effort involved experts from Hungary, England, Japan, and Catalonia, building on tools from Gergely J. Szöllősi's group. Future work aims to apply these methods to other eukaryotes for a refined evolutionary clock.