The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth

by Zoë Schlanger

was an only child for the first nine years of my life, until my brother was born. Even then a newborn wasn’t much use to a nine-year-old girl, especially not one who truly believed she was an adult trapped in a child’s body. Which is to say I was alone and predisposed to fantasy. Girls of that nature tend to build complex internal worlds that they proceed to drape like a blanket over the world around them. Adults who don’t understand this disposition tend to call it melodramatic. But I resented that word, which implied that my version of reality couldn’t be trusted. I was sure I was simply seeing things around me for what they actually were. In most cases, those things were trees and squirrels and sometimes rocks, and they were very much alive, alert to the world. Children are known to be inborn animists.

In The Ecology of Imagination in Childhood, the writer and researcher Edith Cobb spends two decades investigating the role of nature in the early thinking of children.

Nature is not a puzzle waiting to be put together, or a codex waiting to be deciphered. Nature is chaos in motion.

A leaf is the only thing in our known world that can manufacture sugar out of materials—light and air—that have never been alive.

“Of course, the world itself stays the same,” Kuhn wrote. Plants will go on being plants, whatever we decide to think of them. But how we decide to think of them could change everything for us.

From an evolutionary, survival-of-the-fittest perspective, one might think the shyer chipmunks were doomed. But Couchoux found that wasn’t the case. The less aggressive individuals took less risks, so they ate less, and they had fewer babies each year. But they tended to live longer. Less risk-taking meant fewer chances to be gobbled by an eagle. At the opposite end of the spectrum were the really bold chipmunks. “They reproduce earlier, they eat a lot, they take more risks. They will have more babies, let’s say three in one year. But then they die because they are eaten by a predator.

“Their strategies are different, but they can both work for life,” Couchoux says. “This has been found in many species now, from big-horned sheep to fish.” When it comes to personalities, there’s a place for everyone.

In our brain, electricity travels in waves. Information appears on colorized brain scans as pulses, like a wave traveling between two shores. The complexity and coherence of these waves are what neurologists routinely use to determine brain health and mental state. Christof Koch, a chief scientist at the Allen Institute for Brain Science in Seattle, takes it further. He is a fan of a theory developed by neuroscientist Giulio Tononi, which argues that the complexity and integration of these waves are what actually create in us a coherent feeling of reality, one way we sense our own consciousness. Consciousness, Tononi argues,

Their work was based on earlier studies, in which scientists measured electrical impulses in the giant cells of Chara algae, a common pond weed. The Chara cells were enormous, as cells go—ten centimeters long, and a millimeter in diameter—and thus conveniently visible to the naked eye. You could jab an electrode right into one. And they were excitable in much the same way as human cells were. It took a long time for science to begin to ask plants more electrical questions. In 1992, a group of researchers from the UK and New Zealand found that they could block the chemical signaling in tomato seedlings, but that the plants would still accumulate the defensive proteins when another part of the plant was wounded. But they also noted that when a seedling was intentionally wounded, a flurry of electrical activity was detectable. Could the defensive signal be sent by way of electrical impulses, they wondered, instead of chemical ones? In a letter published in Nature, the researchers even went so far as to say that the electrical activity had “similarities to the epithelial conduction system used to transmit a stimulus in the defense responses of some lower animals.” In epithelial conduction, an electric signal is transported cell-to-cell, by way of narrow channels that let ions pass between adjacent cells. “Although plants lack any structures comparable to animal nerves,” they wrote, cells in a plant tissue are linked by narrow threads that have “electrical conductivities nearly...

In 1995, then-president Bill Clinton got word that the U. S. Department of Agriculture was funding studies on “stress in plants” with taxpayer money. He even made a jibe about it in that year’s State of the Union Address, implying that he thought the study was about plants needing psychotherapy, and promised to cut such wasteful spending.

Marcgravia evenia, this ruby-colored sonar reflector, was the second vine found to be acoustically tailored to correspond with bats; the first was a flowering vine that grows on the edge of rain forests across Central America. That vine, Mucuna holtonii, produces many small flowers, and releases its pollen explosively. To reach the nectar, a bat must land on a flower and press its snout into a slit between two winglike petals. The pressure of the push causes a second pair of fused petals within, called a keel, to burst open. Inside the keel, bent under tremendous tension, is a stamen full of pollen. Once the bat bursts the keel, the stamen catapults most of the pollen load onto the bat’s rump.

She has written papers in feminist theory journals that seem to advocate for scientists to use more of a felt sense in their methodologies, acknowledging that this is completely antithetical to how they are trained.

Gagliano spoke at Dartmouth in early 2020, about humbling ourselves as humans: “We are the new kids on the block. Traditionally, you should pay respect to the elders,” by which she meant bacteria, fungi, and plants. She called the view of humanity at the top of an evolutionary chain “arrogant” and “juvenile.” “Who said that science is the only way of knowing? As a scientist, I love science,” Gagliano said at Dartmouth. “I think it’s a beautiful way to describe the world. But it is not the only way.”

With biocommunication, it’s monkey flowers all the way down. De Moraes talks about the “arms race” of insects, plants, and viruses, each outsmarting the other and being outsmarted at turns. “Everybody is trying to survive. All of them.” She often laughs as she explains her findings, as if experiencing her own amazement at the results all over again. I get the sense she isn’t as wedded to this vision of nature as a battlefield, but it’s a metaphor near at hand in all of science since Darwin, so she uses it.

The visual display did something to entice the bees, just as it enticed her. Their beauty, she concluded, was on purpose. Our own subjective sense of beauty could tell us something true about plant intentions after all.

Beauty is almost always a form of communication. Namely, it communicates “choose me.”

The question becomes, in what other ways are they influencing us? A fleet of humans carefully tending a field of crops can certainly start to look like an army of plant symbionts, diligently serving the plants’ needs. I think about Vavilovian mimicry: we didn’t domesticate oats; oats domesticated us. When I look at a field of cabbage or pumpkin or blueberries, I wonder: Have they conscripted a symbiont, and is that symbiont us? But of course we both benefit from that particular form of coercion. Perhaps that’s the way to think about all these layered entanglements: they can be seen as antagonisms, or they can be opportunities for symbiosis, for mutualism. “I think the plants are primary organisms, and we are the secondary ones. We are fully dependent on them. Without them, we would not be able to survive,” Baluška says. “The opposite situation would not be so drastic for them.”

As we walk out of the forest, Gianoli tells me about another strange case of plant mimicry. Chile, he said, is home to a second plant in the same family as the boquila, the Lardizabalaceae family. This species in the genus Lardizabala is an extremely rare climbing vine, growing only in subtropical Chile and parts of Peru. A friend of a friend told him that their uncle lived in a rural village where the lardizabala grew. Its dark purple fruits figured into the village’s medicinal traditions. Gianoli hasn’t been to this village yet, but he says that when something is part of traditional knowledge, it’s likely built upon years of experience and observation. The local lore was that when the lardizabala climbs onto different trees, the fruit that it bears will have medicinal properties similar to those of the tree it climbs on. “So if the properties are digestive, or something related to heart or blood pressure, or other medicinal properties, it is there too.” This suggested a different kind of mimicry entirely. “That the fruit inherits the properties of the tree—this would be amazing,” Gianoli said.

Brain wave synchronization has been found in bats and primates too, which suggests it probably happens in lots of other animals. Clearly, this is a useful phenomenon. Research has found that teams of people perform better when their brain waves are synchronized, that copilots’ brains tend to synchronize during takeoff and landing when collaboration is crucial, and that people who are cognitively in sync report higher feelings of cooperativeness and affinity for each other.

Couples with higher brain synchrony report more satisfaction in their relationships, and brains of coparents appear to sync up in each other’s presence. Our brains evolved in a highly social context, and we are only now seeing how deep that sociality can go. Perhaps this social, collective intelligence deserves its own attention. We may be missing a big part of the story of our own existence without it.

Dudley chalks up this discovery to her choice to temporarily set aside the usual question of how something benefited the plant. Instead, she simply observed what they actually did. “My innovation is that I was asking how plants behave,” she said. Looking at behavior is a different thing from looking at benefits to the plant. Sometimes it can be hard to know what a benefit would look like to a plant, anyhow. Humans don’t always know enough to infer these things. But they can watch and take notes about what’s actually happening in front of them.

others. In 2017 Dudley suggested that crop breeders have been going about their business with a huge blind spot. They have likely been selecting against altruistic plants, to their own detriment. A field without altruistic plants is a field at war. Like any population in wartime, they’ll be thrifty with their energy, and it certainly won’t go toward luxuries like making fruit.

But individual altruistic tendencies may be more clearly distinguishable among them. To develop cultivars in crop breeding, farmers select for the most “vigorous”-looking individual plants in a field. But these are actually the most competitive individuals. The

altruistic tendencies will be more reserved, in that they will tend not to grow aggressively into their neighbor’s sun space. So it seems the history of crop breeding has actually helped to reduce altruism, to its own peril, writes Dudley.

The list goes on and on. Where a plant ends and a fungi

Invasive species have often been maligned as more aggressive, ruthlessly competitive. These are strangely moralizing concepts to put on a plant, when you think about it. The words we use for invasive species are very often unsubtle in their xenophobia, matching nativist language.

But we are the youngest brothers of this family of ours. We haven’t been here that long. Change happens, plant communities fluctuate. Of course, there’s a twist. This era is unique in that we are the ones moving plants around the world. We’ve caused—and are still causing!—most of these invasive species to show up in new places, to adapt to new scenarios and locations. We literally bring them there. It’s even stranger to fault a plant for its successes with this fact in mind.

concrete begins to split open our understanding of plants as sessile,

Humanity has proven its failure as an evolutionary project and chosen a path of generalized destruction. Plants are intelligent, he has written over and over in books and papers. But we have been too slow to notice. It’s probably too late now for that knowledge to change anything in

suppose that’s the nature of pessimism; it forecloses the imagination of hope.

In the world of Ursula K. Le Guin’s 1974 short story The Author of the Acacia Seeds, it might be the year 2200, perhaps 2300.

But I wonder, instead of humanizing plants, could we not just vegetalize our language? We can call these traits plant-memory, plant-language, plant-feeling. The plant-specific essence of each word would stand behind it like a ghost. If plants are intelligent in their own, vegetal manner, perhaps we call that plant intelligence. It rolls right off the tongue.

am quite seriously proposing that we give legal rights to forests, oceans, rivers and other so-called ‘natural objects’ in the environment—indeed, to the natural environment as a whole,” Stone writes; at different points in history, our social “facts,” on which law is often based, have changed. We create a collective “myth” of ourselves and the world, he writes, which reflects our present norms, and is enshrined in our laws. But we tend to forget that these norms are fabrications. “We are inclined to suppose the rightlessness of rightless ‘things’ to be a decree of Nature, not a legal convention acting in support of some status quo,” Stone writes. As our knowledge of “geophysics, biology and the cosmos” grows, so should our collective “myth” and our laws expand with it. The status quo as such is outmoded.

Personhood means one has agency and volition, and the right to exist for their own sake. Harming an animal person (or plant person) may be crucial to one’s ability to survive, but it can’t possibly be disregarded. Yes, you have to eat. You have to make clothing and build houses. You have to kill plant persons and animal persons to do that. That’s a fact of life. But that doesn’t leave any excuse for indiscriminate killing, or thoughtless destruction.