Mushrooms, Time, and the Tree of Life

Hibbett opened by dismantling the assumption that fungi are straightforward. Mushrooms are only the fruiting bodies of certain species; the kingdom also includes yeasts, lichens, filamentous molds, and flagellated swimming cells that resemble sperm. No single morphological or biochemical trait unites them, so they are best defined phylogenetically — as a branch of the tree of life more closely related to animals than to plants. He illustrated their hidden scale with the Armillaria clone in Oregon: a single individual covering 2,000 acres, estimated at 1,900 to 8,700 years old, and roughly the footprint of Logan Airport. About 175,000 fungal species have been described, but estimates of the true total range from 1.5 million to 160 million, and only 0.4% of named fungi have been assessed for conservation status, compared with 80% of vertebrates.

The case for why fungi matter spanned from the grocery aisle to industrial chemistry. They are the basis of bread, beer, wine, and biofuel through yeast fermentation; the original source of penicillin, statins, and many other drugs; and the dominant producers of industrial enzymes, a $14 billion market in 2024. Mycelium itself has become a commodity material, now used in packaging, leather substitutes (including Hermès handbags), and meat analogues. Ecologically, fungi are the master decomposers — effectively the only organisms that fully break down lignin, using enzymes called class II peroxidases to perform white rot. They also form mycorrhizal partnerships with roughly 80% of plant species, and in their pathogenic mode they have shaped human history through chestnut blight, wheat rust, and the Dutch elm disease that erased the elm-tunneled streets of Hibbett's childhood Arlington.

The middle of the talk presented three evolutionary episodes in which fungi played a decisive role but are routinely omitted from textbook timelines of life's history. First, the colonization of land by plants around 460 million years ago appears to have been enabled by a mycorrhizal partnership with arbuscular fungi, which traded soil nutrients for photosynthetic sugars. Second, the end of the Carboniferous period saw a steep decline in coal formation, and Hibbett's group has used phylogenetic reconciliation to date the evolution of white rot decay to roughly the same moment — suggesting the invention of lignin-digesting enzymes may have helped close the window on massive carbon burial. Third, reconstructions of fruiting-body evolution indicate that for the first 150 million years of mushroom history, the dominant form was a simple crust-like "resupinate" morphology; the charismatic capped mushrooms we recognize today did not diversify until the Jurassic and Cretaceous.

The final section turned to the future: the "dark fungi." Since around 2009, next-generation sequencing has let ecologists pull DNA directly from soil and water and detect fungi that have never been collected as physical specimens. These environmental discoveries now vastly outpace traditional taxonomy, which names about 3,000 species per year. But the International Code of Nomenclature — inherited from a 17th-century, pre-evolutionary framework — still requires a physical type specimen for a name to be valid. Hibbett and colleagues have twice proposed allowing sequence-based species descriptions, most recently at the 2024 International Mycological Congress, and both proposals were rejected. A creative attempt to typify sequence-only species through a nomenclature loophole for "works of art" prompted the Nomenclature Committee for Fungi to formally rule that a sequence alignment is not art because it does not depict the organism. At current rates, it will take more than 1,000 years to name every fungal species. "I know that for the Long Now group, 1,000 years is a heartbeat," Hibbett remarked, "but I guess I'm more impatient than you are.

In the Q&A, the conversation ranged across mycoremediation (a field with promising lab results but, Hibbett cautioned, no proven field-scale application yet), fungal burial shrouds (conceptually beautiful but ecologically misguided, since bacteria, not oyster mushrooms, decompose vertebrate bodies), and the thermotolerance hypothesis linking climate change to emerging human fungal pathogens like Candida auris. Asked whether a mushroom could serve as the basis for a 10,000-year clock to rival Long Now's own, Hibbett suggested tracking a front of decay over time — a cool idea, he allowed, but not one he had worked out.