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

by Zoë Schlanger

Boquila, a truly dynamic chameleon, was the first species found to imitate more than one other plant. There is only one other plant known to do anything close to this. Mistletoe, our sometime symbol of romantic love, is a parasitic plant. Like all parasitic plants, it sinks tendrils into its host plant, often a eucalyptus or acacia tree, and sucks out the nutrients it needs to survive, instead of making them itself. Very romantic.

I think of cuttlefish, which are colorblind, yet also able to “see” with their skin, instantly mimicking the color and texture of a pile of marine rock or cluster of coral to disappear in the background, hidden from predators in plain sight.

Gianoli talks about the fact that termites were recently discovered to have microbes in their guts that make it possible for them to digest the chemicals in wood. In other words, the most signature behavior of termites—wood-eating—is made possible by entirely different organisms living within them. The termite’s gut microbes, in turn, are able to function thanks to yet smaller microbes that live within them. The presence of these animals-inside-animals predates the evolution of the termite itself—some termite ancestor likely acquired them by eating dead plant material where microbes were living. From there, both evolved together into the versions of each that exists today. One species of Australian termite is known to have a protist in its gut that in turn carries around four types of bacteria of its own. So many cascading individuals make a termite possible.

Humans, too, are composite organisms, he reminds me: our own microbiomes appear to govern many aspects of our health, and possibly even our psychology. “They’re related to digestion, allergies, even certain psychological disorders,” he says.

I thought about Buddhist meditation, in which the goal is to dissolve the self. Of course, one must know what the self is before it can be annihilated. The way the “self” is described in Vipassana, a form of Buddhist meditation, is as a collection of tiny, quivering units. Some call them atoms. At the root, though, is the idea that we are not ourselves—rather, we are only the sum of a bunch of individual flecks that happen to be humming along in the shape of a person. The self is dissolved when that is understood.

One begins to see the world in bacterial terms—a microcosmic sea of shifting identity and form. Under the surface, our bacterial selves are morphing and changing. We are all in flux.

Once upon a time, certain insects evolved to be social in a very particular way. They evolved to be fully devoted, each of them, to the well-being of the larger group in which they lived. Their identities became wholly subsumed into supporting the collective. These are the colony dwellers. Everyone in the colony has a role, and to fulfill it some forgo even the activity most often seen as a marker of biological success: they never reproduce at all. Instead, these insects spend their lives foraging for food to bring back to their nest-mates, whose role it is to have the babies. This turns the idea of survival of the fittest on its head. In a colony like this, self-interest is subverted for the sake of group interest.

An entomologist in the 1960s named this lifestyle “eusocial” behavior, and first applied it to bees who live in hives, with multiple generations that take cooperative care of their young, and have distinct roles where only some reproduce. Eusocial literally means “truly social.” It’s a highly complex social lifestyle, full of defined rules of relationality and collaboration. It has since been found to apply to lots of insects, not just bees; termites are eusocial, as are ants, ambrosia beetles, and at least one type of aphid. A coral reef-dwelling shrimp can be eusocial, extending the concept to the world of crustaceans. And naked mole rats have the honor of being the breakout stars of eusociality in mammals. Insects, crustaceans, mammals: eusocial behavior must have evolved separately many times. Clearly it is an evolutionary strategy for success, or it wouldn’t have spontaneously reappeared and persisted across distinct branches of life.

There is still much we don’t know about soil and its pulsing community of life. There are as many as one billion microbes in a teaspoon of soil. Fungi weave their networks of hair-fine threads through nearly every square inch of ground.

The sweetness of tomatoes, the aromatic qualities of basil, and the properties of the essential oil in mint have all been shown to change depending on the species of fungi the plant grows with. The concentrations of medicinal compounds in echinacea, the aromatics in patchouli, and the antioxidant power of artichoke heads have all been found to increase with the presence of certain fungal associates too. The list goes on and on. Where a plant ends and a fungi begins becomes hard to parse. In fact it seems hardly a stretch to ask whether a plant is itself without fungi.

Sunflowers are known allelopathics, meaning that they will secrete chemicals into the soil when resources are low to stop the germination of seedlings of other plants. As such, sunflowers are often good guards against invading weeds in garden patches.

People with the “lung cancer gene” are much more likely to develop lung cancer, especially if they smoke. Due to genetic mutations, they lack a certain enzyme that most people have, which normally works to clear cancer-causing chemicals from hazards like tobacco smoke out of the lungs. So that was one trend line, at a steep angle upward; the more these “lung cancer gene” people smoked, the more likely they were to get lung cancer. But then she drew a second line and labeled it “broccoli.” People with the lung cancer gene who ate a significant amount of cruciferous vegetables, including broccoli, appeared to have a lower risk of lung cancer proportional to how much broccoli they ate. At high enough intake, broccoli nearly erased the impact of the gene mutation. (In a different study, it even appeared to help people without the genetic anomaly clear carcinogens from smoking.) This is likely because cruciferous vegetables like broccoli produce compounds that, when broken down in our bodies, turn into the enzymes that detoxify cancer-causing chemicals. In other words, these vegetables make the thing that does what the “lung cancer gene” people lacked the genetic ability to do. Here, genes weren’t everything. The environment a person experienced—in this case, what they ate—had a place in the story too. Possibly even a bigger place than genes.

Consider the emerald green sea slug. When I first read about it, I couldn’t stop talking about it with anyone who asked what was going on with me lately. The green sea slug, this whimsical thing that seemed to defy all boundaries between plant and animal, was going on with me. It was all I could think about. The slug, which lives in watery places all along the Atlantic coast of the United States, spends its early life a brownish color with a few red dots. It has one goal in those early moments: to locate the hairlike strands of the green algae Vaucheria litorea. When it finds them, it punctures the alga’s wall and begins to slurp out its cells as though through a straw, leaving the clear tube of empty algae behind. The algal cells are bright green, owing to the chlorophyll-filled chloroplasts inside them, which are responsible for photosynthesis. Under a microscope the whole exchange looks uncannily like the slug is drinking bubble tea, one bright green boba entering its mouth at a time. The slug digests the cells but keeps the chloroplasts within them intact, spreading them out through its branched gut. Now the slug itself has turned from brown to a brilliant green. After a few algal bubble teas, the slug never needs to eat again. It begins to photosynthesize. It gets all the energy it needs from the sun, having somehow also acquired the genetic ability to run the chloroplasts, eating light, exactly like a plant. How this is possible is still unknown. Remarkably, the now-...

The idea that everything is interconnected came through like a powerful chime. Everything is quite literally interconnected.

We are more like a system than a single unit. All biology is ecology. Plants remind us that we are contiguous with our environment, impacted by its every fluctuation, impacts that reverberate through our lineage. Our environment shapes our lives and the lives of our descendants. We inherit their environment in bodily form. One could say we inherit the earth.

Every inward breath of mine was first breathed out by plants. In this material sense, in terms of what they’ve contributed to my physical being, they are as much my relatives as any family member I know.

As we’ve already learned, Native philosophies from all corners of the globe often understand plants as relatives, or ancestors, or otherwise persons in their own right. It’s not that plants are human, but that humans are just one kind of person, as are animals. 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.

Báyò Akómoláfé, a Yoruba poet and philosopher, wrote about this in-betweenness, contemplating the way all creatures are in fact composite organisms. The state of nature is one of interpenetration and mingling that defies easy categorization. It occupies a middle place, both in the material reality of the world and in our understanding of it. “The middle I speak of is not halfway between two poles; it is porousness that mocks the very idea of separation,” he writes. Akómoláfé outlines our collective biological reality as a state of “brilliant betweenness” that “defeats everything, corrodes every boundary, spills through marked territory, and crosses out every confident line.”

The trying says more about what is inside us than does the success. Again, there are no foregone conclusions. If I’ve learned anything, it’s that biotic creativity is our inheritance.

A single plant is a marvel. A community of plants is life itself. It is the evolutionary past and future entangled into a riotous present in which we are ourselves also entangled.