Down the Rabbit Hole with Our Least Known Kin
Your cousins are fungi, and the survival of life on Earth depends on them.
by Richard Conniff
Early this week—the big snow day here in New England—Substack tumbled me boots-over-teakettle down a rabbit hole. It was a more-or-less healthy, not too disorienting rabbit hole, on an Alice in Wonderland sort of topic—mushrooms, lichens, and fungi more generally.
The rabbit hole started with a dazzling series of photos of turkey tail mushrooms taken in Hertfordshire, England, by Gem at Birdfolk. That bounced me along, by way
of a restack, to a photo by my Substack friend Jessica Groenendijk asking “what the heck is this?” about a beautiful … thingy (below), which she found at 13,000+ feet in Quito, Ecuador. It seems, said her readers, to be a lichen in blossom, possibly Phyllobaeis. One reader, a Substack friend named Jim Colbert, also saw a resemblance to a North American species commonly known as “fairy puke lichen.”
“I love fairy puke,” came the reply, from a self-described “death doula, writer, and mushroom forager studying eco theology.” This rabbit hole was starting to feel weird and cozy at the same time. For one morning, anyway, it felt like a blessed relief from having to think about the Trumpian hatred and brutality in the streets outside our doors.
But let me get to the point. As an amateur naturalist, I have been struggling for a while now to make sense of fungi—that is, to understand what they are and how they fit into the big picture of life on Earth. There are good reasons we should know: Fungi are, to begin, astonishingly abundant, with an estimated 2.5 million species worldwide (or possibly double that), though only 155,000 have been described so far. They seem to be everywhere, from the desert to the deep ocean to the Antarctic. Many of them are microscopic. But I have seen lichens splashed across large expanses of rock. And a fungus named Armillaria ostoyae, better known as “the humongous fungus,” inhabits 3.5 miles of land, mostly underground, in Oregon's Malheur National Forest and may be the largest organism on Earth.
Fungi also seem to play a role in almost everything, especially as scientists have begun to exam them more closely. For dinner last night, to take a familiar example, I made a no-knead pizza dough, added the usual toppings, and ate it with a beer on the side. Both the dough and the beer are of course products of yeast, which is a fungus. I digested this meal with the help of fungi living in my mouth and gut, where they play an important part not just in digestion but also in mental health. Likewise, having the right mix of fungi around the roots of the right plant species—for instance, the tomatoes in the sauce on my pizza—has turned out to be a key determinant of whether the plant lives, becomes productive, and is able to adapt to climate change.
I have often blundered through the fungal world incidentally on assignments as a writer about the natural world. In the Amazon, for instance, I once witnessed the ghastly, thready growths of a parasitic Cordyceps fungus bursting from the head of a living wasp. I also once ate a Cordyceps fungus in a mountaintop monastery in Bhutan. I did it mainly to be polite to my hosts, who seemed to regard it as an almost sacred treat, or possibly as their version of Viagra. This was long before the apocalyptic hit television series “The Last of Us” made people a little nutty on the pandemic possibilities of Cordyceps. In any case, there were no noticeable effects, good or ill.
My fungal tumble down the rabbit hole took one more surprising turn. That same morning, on another online venue, my friend Harry W. Greene, a retired herpetology and ecology professor from Cornell University now living in Texas, posted this photo:
Still a professor at heart, Harry added a spot quiz:
OK Tree of Life fans …
1) Who’s more closely related to these organisms, me or a pine tree?
2) What’s the name that encompasses me, a pine tree, and mushrooms?
3) What’s a defining characteristic of all three?
4) Was the common ancestor of all three one-celled or multi-cellular?
I immediately closed my empty blue book, stood up, and walked out of the room intent on taking my failing grade with grace. Then I went home and looked up the answers: (1) you—that is, humans are more closely related to fungi than to plants, 2) all three are eukaryotes, 3) That means our cells have a membrane-bound nucleus containing DNA, and 4) humans, the pine tree, and the mushrooms shared a single-celled common ancestor.
Even scientists, I learned on further reading, had no clue what fungi were all about until recently, except that they did not seem to belong in the animal kingdom. So for more than 230 years, on the rare occasions naturalists bothered to notice them at all, fungi got dumped into the plant kingdom. The notion that all living things fell into just those two kingdoms came from the eighteenth-century biological organizer Carolus Linnaeus. It wasn’t until 1969, a few months ahead of the moon landing, that classification of life on Earth got expanded to five kingdoms, including one for fungi.
The close connection between fungi and humans—well, animals more generally—was first suggested in 1987 by an Oxford evolutionist named Thomas Cavalier-Smith, who called us “Opisthokonts,” which has a nice ring to it. I’m going to pretend it means that we are classy sort of organisms. Genetic research since then has confirmed the connection. Early primitive plants split off from our last common single-celled ancestor about 1.5 billion years ago, while early animals and fungi evolved together for eons after that, only splitting off from our last common ancestor 800 or 900 million years ago.
That’s not yesterday. But it’s close enough, says Jessica Allen, a mycologist with the nonprofit NatureServe, that, “at a cellular level, we share a lot of similarities with fungi. It’s part of what makes treating human fungal pathogens so hard.” For instance, Candida auris, a yeast, was first identified only in 2009 in Tokyo. But it now causes multi-drug resistant infections worldwide in patients with weakened immune systems, spreading mainly in nursing homes and other healthcare settings.
At the same time, adds Allen, “the close cellular connection is part of why fungal-derived compounds have a lot of potential utility for human health.” Dozens of drugs that got started from fungi are already in routine use, for anti-fungal, anti-depressant, anti-inflammatory, and even anti-cancer purposes. Penicillin, mass-produced from a fungus found on a rotten grapefruit in a grocery store in Peoria, Indiana, launched the antibiotic era and has saved scores (and perhaps hundreds) of millions of lives, starting with the Allied soldiers who carried it ashore on D-Day 1944. The first cholesterol-lowering drug, Lovastatin, in 1987, was also based on a fungal compound.
“Almost every single species produces a different suite of compounds,” says Allen, numbering from five to 70 compounds per species. “The genes underlying them just seem to evolve really quickly. From an evolutionary perspective, this makes a lot of sense. Most of the ways that fungi mediate interactions with their environment are through chemical interactions.”
So fungi are also the subject of intense bioprospecting research for industry. Current commercial applications range from food production (initiating fermentation for your favorite soy sauce or miso, for instance) to pollution remediation (breaking down hydrocarbons, heavy metals, and pesticides).
The hitch, as with almost all living things, is that fungi are threatened and in decline because of human activity—meaning the usual suspects, like habitat loss, air and water pollution, logging, agricultural land-clearing, wildfires, and climate change.
“We don’t do very much to conserve them,” says Allen. In truth, even conservation groups barely recognize their existence. The Red List of the International Union for Conservation of Nature (IUCN) is an exception. It currently names 1000 fungus species worldwide in danger of extinction. Branden Holmes, an independent researcher in Australia, also maintains a database of dozens of fungal species thought to have become extinct in recent times. The U.S. Endangered Species Act has listed two East Coast lichen species for the past 30 years, but it hasn’t led to a species recovery program for either.
Allen recently joined NatureServe to change that, by adding fungi to the essential natural heritage data the organization currently provides to state, provincial, and federal government agencies in the United States and Canada. The aim is to bring fungi up to speed with the plants and animals that depend on them.
“That’s pretty exciting,” she says. Fungi “are the most biodiverse and understudied groups of organisms on the planet and and at the same time, they’re absolutely essential to all of our functioning ecosystems … and to the health of our planet.”
On that thought, let’s fade out with the 1958 novelty hit “Fungus Among Us,” by the Texas rockabilly singer Terry Noland:
Or, if you prefer, Jefferson Airplane performing “White Rabbit” at Woodstock:
Other Reading and Viewing:
Robbins, Jim; March 12 2026 Long Overlooked as Crucial to Life, Fungi Start to Get Their Due
Fascinating! I knew fungi had their own kingdom, but not that they're more closely related to us than plants - so cool! I just love how complex and intricate nature is, it's humbling to realize how much humans don't know about life on our own planet. Thanks for a great rabbit hole I could explore this morning.
It’s a wonder Zappa never did a tune featuring fungus. Or did he?