To most of us, mushrooms are just weird-looking woodland growths, and a fungus is something you probably need a cream for. Increasingly, though, scientists are describing fungi as more sophisticated than we previously thought.
Some even say 'intelligent', with a few researchers going so far as to hint they might be conscious.
While such theories are controversial among experts, the rest of us would like to know if, for instance, our breakfast ingredients are thinking about us. So, what should we make of such reports?
Biologists have long argued over whether animals like fish and bats are conscious. But now brainless beings like plants, slime moulds and fungi are getting caught up in the debate.
And there’s certainly more to mushrooms than meets the eye, as Cecelia Stokes, a PhD fungi researcher at the University of Wisconsin-Madison, in the US, explains.
Below ground, mushrooms are attached to a mycelium web of wire-like filaments, called ‘hyphae’ that stretch through the soil to seek out food and mates. The mushrooms, above ground, are the fruiting body – the fungi’s spore- spreading reproductive organs.
“[Fungi have] developed a really efficient and effective way of navigating minute changes in their environment,” says Stokes. “And that alone – doing it without a central nervous system or a brain – is amazing.”
Whether this kind of behaviour demonstrates intelligence, she isn’t sure, but she says it might be “worth considering” a wider definition of the term, given that it’s already being applied to the non-living, as with artificial intelligence, for instance.
Newfound appreciation
Fungi have gone up in our estimations in recent years, following claims that their hyphae from nutrient-swapping networks with trees that connect up the forest – the so-called ‘wood wide web’ theory.
And they’ve gained some street cred as the agents of a zombie apocalypse in the popular video game and HBO show, The Last of Us.
Now, though, new studies imply fungi are capable of behaviours usually reserved for humans and other animals, such as learning, remembering and decision-making.
Dr Yu Fukasawa and his team at Tohoku University in Japan observed this behaviour when ‘baiting’ the wood-decomposing fungus, Phanerochaete velutina, with wood blocks on soil.
In one 2020 study, Fukasawa and UK colleagues saw the fungi ‘decide’ when to give up one block in favour of another, bigger piece of wood. The fungi also ‘remembered’ the direction they grew in to find the wood, even after being moved to new ground.
For Fukasawa, these were expressions of intelligent behaviour. “It is, of course, not the same system as a brain,” he says, explaining that the fungi’s ability to ‘remember’ is probably based on having grown more on the side where the bait blocks were originally positioned.
“But I think we can say that it is a kind of memory in the mycelial system – a kind of structural memory.”
Slime moulds have also been said to have memory because they avoid previously explored areas when searching for food. In their case, they’re able to sense slime in the areas they’ve already covered.
Last year, Fukasawa’s team attempted a new experiment, this time exploring whether fungi could ‘recognise’ shapes.
Using nine blocks laid out on the soil – in either the shape of a cross or a circle – they observed the fungi growing from the centre outwards. In the case of the cross, the fungi eventually left the middle blocks for the outer ones, as they searched further afield for more wood.
While Fukasawa notes that what they saw is just the fungi’s natural response to using up the resources in the centre, he still views it as “very intelligent.” The fact that the fungi distinguish between inward and outward means they can recognise spatial direction, he explains.
In the paper they published, the researchers call this behaviour a form of ‘pattern recognition’, a term used in computing to describe how they’re able to spot certain combinations in data, but which can also be used to describe how people recognise faces or sounds.
In the case of the circle, the fungi left the centre uncovered, suggesting they ‘decided’ there was already enough food on offer at the perimeter and communicated this throughout their network.
Given his findings, Fukasawa thinks there’s merit in viewing intelligence as more of a sliding scale. “Because, in that condition, we can discuss intelligence in more broad terms and make comparisons between us and different organisms,” he says.
"If we define intelligence only for human brains, we can't discuss the evolution of intelligence."
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Expanded views
Along the way, experiments like Fukasawa’s have encouraged some to entertain more eye-opening theories about fungal consciousness, such as fungal biologist Dr Nicholas Money’s, “fungal mind.”
He suggested a basic premise in an essay in Psyche magazine in 2021, that fungi could be regarded as conscious, if we’re willing to expand our view of what consciousness actually is.
In the paper, Money proposes that we “allow ourselves to identify different versions of consciousness across a continuum of species, from apes to amoebas.”
Other concepts of primitive minds include “liquid brains”, which could account for how slime moulds and some other microbial communities process information without neurons.
Meanwhile, electrical signals detected in fungi have been likened to the electrical signals associated with nerve cells in animals, leading some to ask whether fungi have a form of brainless nervous system. Similar arguments have been made for plants.
For Fukasawa, however, whether or not fungi are conscious isn’t the question. “For me, it isn’t so important if fungi are conscious because they can [show] intelligent behaviour and they can solve their own problems in life,” he says.
Meanwhile, Stokes says consciousness is too much of a stretch. Although she agrees that putting fungi in the same box as humans and other animals can help them seem more relevant to us, the science “hasn’t caught up to the narrative” yet.
By making these comparisons, she says, “We’re dismissing a lot of really fascinating biology they have that’s different from us.”
Theory vs evidence
Humans have a tendency to compare, though, so what of the claims of brainless nervous systems? According to Stokes, it isn't surprising that we're able to detect electrical signals in fungi or plants.
“All cells generate electricity from movement of ions across membranes,” she says. Moving ions (charged atoms or molecules) around is a crucial part of what cells do to make energy and signal to neighbouring cells.
It’s just that the electrical signals that drive our nerve impulses are the result of ions arriving at the membrane of a nerve cell.
Yet, it’s easy to dismiss theories of fungal intelligence and consciousness as eccentric, but perhaps instead it’s worth exploring what’s driving the theories.
Often it’s a desire to make organisms that seem almost alien to us more relatable. Giving a species human characteristics can, in some cases, persuade us to protect them.
In the case of the wood wide web, however, some scientists are now arguing that the theory has gone too far. The idea that trees communicate with each other via fungal networks is being stated as fact, when the truth is that the evidence for it remains thin.
Similarly, defining fungi as conscious under current definitions seems premature and could interfere with conservation efforts. On the other hand, if you change the definition, you can say what you like. But why bother?
"We don’t need human characteristics to think about how cool fungi are,” says Stokes, whose own research focuses on the poisonous ‘death cap’ mushroom.
About our experts
Cecelia Stokes is a PhD fungi researcher at the University of Wisconsin-Madison, in the US. She is published in the scientific journal, New Phytologist.
Dr Yu Fukasawa is an associate professor of Forest Microbial Ecology at Tohoku University, in Japan. His work has been published in the likes of Multidisciplinary Journal of Microbial Ecology, Fungal Ecology and Forest Ecology and Management.
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