We've reached the end of the series, so let's end where this kingdom actually leaves us: mostly in the dark. After five letters of genuinely astonishing things — fungi aren't plants, they're your cousins, they eat the world from the outside, they may have greened the land, the biggest one alive sprawls across square miles of Oregon — here's the punchline that ties it all together.
We've barely met this kingdom at all.
Not as a figure of speech. As arithmetic. And the honest version of that arithmetic is the perfect note to close on, because uncertainty isn't a gap in this story. For Crazy Organic, it is the story.
The numbers
Roughly 150,000 species of fungi have been formally described — named, written up, filed in the scientific record. That sounds like a lot. Here's the catch: the best modern estimates put the true number of fungal species somewhere between 2.2 and 3.8 million. Some estimates run higher still. Contested
Do that division and it's staggering. If the real total is in the low millions, then everything we've named — every mushroom in every field guide, every mold and yeast and blight humanity has ever catalogued — is only about 3 to 8 percent of the kingdom. We've met maybe one fungal species in twenty. The other nineteen are out there, unnamed, undescribed, unknown.
But we have to be honest about that big number, and the honesty is itself the interesting part: the 2.2-to-3.8-million figure is a contested estimate, not a measured fact. It's a careful, modeled projection — and the projection has its own history. For decades the working benchmark was the mycologist David Hawksworth's 1991 estimate of 1.5 million species. Then DNA surveys started sampling fungi straight from soil and water and the insides of other organisms — and revealed how much we'd been missing, sharply pushing the number upward to today's 2.2–3.8 million range. So when we say "we've named one in twenty," we're doing arithmetic on top of a denominator that is itself an active scientific estimate. The under-counting is certain. The exact multiple is not. Both of those are worth saying. Contested
Why a whole kingdom stayed hidden
How do you overlook millions of species? It seems impossible until you remember what a fungus actually is (Eps. 3 and 5): mostly an invisible web threaded through soil, wood, or the bodies of other living things, fruiting rarely or never into anything you'd notice. We mostly met the show-offs — the ones that push up conspicuous mushrooms. That's a tiny, flamboyant minority of the kingdom. The vast majority lives and dies without ever raising a visible flag, microscopic and hidden, exactly where we weren't looking. Established
And the science is young, too
Here's the part that surprised us most. The systematic study of fungi — mycology — is a remarkably recent science. Pier Antonio Micheli, an Italian botanist, is widely regarded as its founder: his Nova plantarum genera (1729) was the first work to describe fungal spores observed under a microscope. Established Before then, where fungi even came from was genuinely mysterious. Modern mycology — working out fungal life cycles, how fungi cause disease — really took shape only in the 1800s, with figures like Anton de Bary, often called the founder of modern mycology.
Sit with that timeline against the others in this series. We've been formally naming fungi for under three centuries, seriously understanding them for under two — for an entire kingdom of life as old and vast and strange as this one. We are, genuinely, still early.
The honest finale
So this is where we land, and it's home turf for everything Crazy Organic is about. The unexplored kingdom is not a tidy story with a bow on it. It's a frontier where "we don't know yet" is simply, gloriously true — true about how many fungi there are, true about what the giants of the deep past were, true about where the deepest branches of life belong (remember Ep. 1 — we're still arguing about that).
Most of science writing treats the unknown as an embarrassment to be hurried past. We think it's the best part. An entire branch of life — your weird, world-digesting, planet-greening cousins — is sitting mostly unmet under your feet, and the work of meeting it has barely begun. The gap isn't a flaw in the story.
The gap is the story. And it's exactly where the rest of Crazy Organic begins.
Thanks for walking through the kingdom with us. There's so much more ground to cover — fungal networks that might solve mazes, the question of whether anything without a brain can "think," what an individual even is. We'll see you out there.