Life › Complex cells & first multicellular life › Multicellular life
Fungi
possibly c. 1 billion years ago (debated fossils)· Organism or group· Plants & fungi
DebatedScientists disagree about when, how or why.
The kingdom of mushrooms, molds and yeasts, closer relatives of animals than of plants, whose fossil beginnings are debated.
See it on the Life map →What happened
Fungi grow as threads (hyphae) that form networks called mycelia, digest food outside their bodies and build walls of chitin, the same material as insect shells. Genes place them on the same branch of the tree of life as animals (the opisthokonts). Molecular clocks suggest an origin around a billion years ago or earlier. Claimed early fossils include Ourasphaira, about 1 billion years old, from Arctic Canada (reported 2019). Undisputed fungi are preserved in the 407-million-year-old Rhynie Chert of Scotland.
Why it matters
As decomposers and partners of plant roots, fungi recycle nutrients and helped plants colonize land. Their multicellularity evolved separately from that of plants and animals.
The evidence (fossils, genes, rocks)
Gene trees, chitin detected in Ourasphaira fossils, fungus-like filaments about 810–715 million years old from rocks in Congo, and clear fossils in the Rhynie Chert.
Still debated
Whether the billion-year-old fossils are really fungi, and whether fungi lived on land long before plants.
Connections (3)
▸Multicellular life arose independently in FungiStrong evidence
The connection
Fungi evolved many-celled bodies on their own, separately from plants and animals. Their networks of threads (hyphae) share cell contents and nutrients, a very different design from animal tissues. Mushrooms are the fruiting bodies of these networks, and complex forms may have evolved more than once within fungi.
When and how
Possibly around a billion years ago, though fungal fossils that old are debated; mushroom-forming fungi came far later.
How sure are we?
Gene trees place fungi closer to animals than plants, yet the genes behind their multicellular growth differ, indicating an independent origin.
Debates and open questions
How many times complex multicellularity arose within fungi, and what the earliest fungal bodies looked like.
▸Fungi formed Plant–fungus partnerships (mycorrhizae)Strong evidence
The connection
Fungi feed by absorbing nutrients through networks of fine threads (hyphae). Some fungi came to live in and around plants, trading minerals and water pulled from the ground for the plant's sugars. These partnerships were formed by early fungal groups related to today's Glomeromycota and Mucoromycotina.
When and how
From early land plants, perhaps 470 million years ago; preserved in Scotland's Rhynie chert, about 407 million years ago.
How sure are we?
Fossil fungi inside Rhynie plant cells resemble living mycorrhizal fungi, and DNA family trees date these fungal groups to before or alongside land plants.
Debates and open questions
Fungi may be a billion years old, based on debated fossils; when they first met plants, and which group partnered first, is unresolved.
▸Why so much coal? The wood-rot debate asks when wood-rotting evolved in FungiDebated
The connection
White-rot fungi are the main organisms that can fully break down lignin. The 2012 study compared 31 fungal genomes and used a molecular clock to date their lignin-dissolving enzymes to about 295 million years ago, near the end of the coal age. If wood-rot came that late, buried wood could escape decay and become coal.
When and how
David Floudas, David Hibbett and colleagues, Science, 2012, building on a 1990 proposal by Jennifer Robinson.
How sure are we?
The enzyme dates come from molecular clocks, which have wide error bars; fossil fungi and decayed fossil wood offer only limited direct checks.
Debates and open questions
Whether wood-rot evolved earlier than the clock suggests, and whether other fungi or bacteria could already break down lignin, are open questions.