On a freezing day in December 2021, I arrived in Madison, Wisconsin, to visit Simon Gilroy’s lab. In one room of the lab sat a flat of young tobacco and Arabidopsis plants, each imbued with fluorescent proteins derived from jellyfish.

Researchers led me into a small microscope room. One of them turned off the lights, and another handed me a pair of tweezers that had been dipped in a solution of glutamate—one of the most important neurotransmitters in our brains and, research has recently found, one that boosts plants’ signals too. “Be sure to cross the midrib,” Jessica Cisneros Fernandez, then a molecular biologist on Gilroy’s team, told me. She pointed to the thick vein running down the middle of a tiny leaf. This vein is the plant’s information superhighway. Injure the vein, and the pulse will move all over the plant in a wave. I pinched hard.

On a screen attached to the microscope, I watched the plant light up, its veins blazing like a neon sign. As the green glow moved from the wound site outward in a fluorescent ripple, I was reminded of the branching pattern of human nerves. The plant was becoming aware, in its own way, of my touch.

But what exactly does it mean for a plant to be aware ? Consciousness was once seen as belonging solely to humans and a short list of nonhuman animals that clearly act with intention. Yet seemingly everywhere researchers look, they are finding that there is more to the inner lives of animals than we ever thought possible. Scientists now talk regularly about animal cognition; they study the behaviors of individual animals, and occasionally ascribe personalities to them.

Some scientists now posit that plants should likewise be considered intelligent. Plants have been found to show sensitivity to sound, store information to be accessed later, and communicate among their kind—and even, in a sense, with particular animals. We determine intelligence in ourselves and certain other species through inference—by observing how an organism behaves, not by looking for a psychological sign. If plants can do things that we consider indications of intelligence in animals, this camp of botanists argues, then why shouldn’t we use the language of intelligence to describe them too?

[From the July/August 2021 issue: A better way to look at trees]

It’s a daring question, currently being debated in labs and academic journals. Not so long ago, treading even lightly in this domain could upend a scientist’s career. And plenty of botanists still think that applying concepts such as consciousness to plants does a disservice to their essential plantness. Yet even many of these scientists are awed by what we are learning about plants’ capabilities.

A single book nearly snuffed out the field of plant-behavior research for good. The Secret Life of Plants, published in 1973, was as popular as it was irresponsible; though it included real science, it also featured wildly unscientific projection. One chapter suggested that plants could feel and hear—and that they preferred Beethoven to rock and roll. Another suggested that a plant could respond to malevolent thoughts.

Many scientists tried to reproduce the most tantalizing “research” presented in The Secret Life of Plants, to no avail. According to several researchers I spoke with, this caused the twin gatekeepers of science-funding boards and peer-review boards to become skittish about plant-behavior studies. Proposals with so much as a whiff of inquiry into the subject were turned down. Pioneers in the field changed course or left the sciences altogether.

A decade after the book’s publication, a paper by David Rhoades, a zoologist and chemist at the University of Washington, reopened questions of plant communication. Rhoades had watched a nearby forest be decimated by an invasion of caterpillars. But then something suddenly changed; the caterpillars began to die. Why? The answer, Rhoades discovered, was that the trees were communicating with one another. Trees that the caterpillars hadn’t yet reached were ready: They’d changed the composition of their leaves, turning them into weapons that would poison, and eventually kill, the caterpillars.

Scientists were beginning to understand that trees communicate through their roots, but this was different. The trees, too far apart to be connected by a root system, were signaling to one another through the air. Plants are tremendous at chemical synthesis, Rhoades knew. And certain plant chemicals drift through the air. Everyone already understood that ripening fruit produces airborne ethylene, for example, which prompts nearby fruit to ripen too. It wasn’t unreasonable to imagine that plant chemicals containing other information—say, that the forest was under attack—might also drift through the air.

[Read: A glowing petunia could radicalize your view of plants]

Still, the idea that a plant would defend itself in this way was heretical to the whole premise of how scientists thought plants worked. Plants were not supposed to be that active, or have such dramatic and strategic reactions. Rhoades presented his hypothesis at conferences, but mainstream scientific journals were reluctant to take the risk of publishing something so outlandish. The discovery ended up buried in an obscure volume, and Rhoades was ridiculed by peers in journals and at conferences.

But Rhoades’s communication experiments, and others that came immediately after, helped establish new lines of inquiry. We now know that plants’ chemical signals are decipherable not just by other plants but in some cases by insects. Still, four decades on, the idea that plants might communicate intentionally with one another remains a controversial concept in botany.

One key problem is that there is no agreed-upon definition of communication, not even in animals. Does a signal need to be sent purposefully? Does it need to provoke a response in the receiver? Much as consciousness and intelligence have no settled definition, communication slip-slides between the realms of philosophy and science, finding secure footing in neither. Intention poses the hardest of problems, because it cannot be directly determined.

[From the March 2019 issue: A journey into the animal mind]

The likely impossibility of establishing intentionality in plants, though, is no deterrent to Simon Gilroy’s sense of wonder at their liveliness. In the ’80s, Gilroy, who is British, studied at Edinburgh University under Anthony Trewavas, a renowned plant physiologist. Since then, Trewavas has begun using provocative language to talk about plants, aligning himself with a group of botanists and biologists who call themselves plant neurobiologists, and publishing papers and a book laying out scientific arguments in favor of plant intelligence and consciousness. Gilroy himself is more circumspect, unwilling to talk about either of those things, but he still works with Trewavas. Recently, the two have been developing a theory of agency for plants.

Gilroy is quick to remind me that he is talking strictly about biological agency, not implying intention in a thoughts-and-feelings sense. But there’s no question that plants are engaged in the active pursuit of their own goals and, in the process, shape the very environment they find themselves rooted in. That, for him, is proof of plants’ agency. Still, the proof is found through inferring the meaning behind plants’ actions rather than understanding their mechanics.

“When you get down to the machinery that allows those calculations to occur, we don’t have the luxury of going, Ah, it’s neurons in the brain,” Gilroy told me. His work is beginning to allow us to watch the information processing happen, “but at the moment, we don’t know how it works.”

That is the essential question of plant intelligence: How does something without a brain coordinate a response to stimuli? How does information about the world get translated into action that benefits the plant? How can the plant sense its world without a centralized place to parse that information?

A few years back, Gilroy and his colleague Masatsugu Toyota thought they’d have a go at those questions, which led them to the experiment I participated in at the lab. Their work has shown that those glowing-green signals move much faster than would be expected from simple diffusion. They move at the speed of some electrical signals, which they may be. Or, as new research suggests, they may be surprisingly fast chemical signals.

Given what we know about the dynamics of sensing in creatures that have a brain, the lack of one should mean that any information generated from sensing ought to ripple meaninglessly through the plant body without producing more than a highly localized response. But it doesn’t. A tobacco plant touched in one place will experience that stimulus throughout its whole body.

The system overall works a bit like an animal nervous system, and might even employ similar molecular players. Gilroy, for his part, does not want to call it a nervous system, but others have written that he and Toyota have found “nervous system–like signaling” in plants. The issue has even leaked out of plant science: Researchers from other disciplines are weighing in. Rodolfo Llinás, a neuroscientist at NYU, and Sergio Miguel Tomé, a colleague at the University of Salamanca, in Spain, have argued that it makes no sense to define a nervous system as something only animals can have rather than defining it as a physiological system that could be present in other organisms, if in a different form.

Convergent evolution, they argue, wherein organisms separately evolve similar systems to deal with similar challenges, happens all the time; a classic example is wings. Flight evolved separately in birds, bats, and insects, but to comparable effect. Eyes are another example; the eye lens has evolved separately several times.

The nervous system can reasonably be imagined as another case of convergent evolution, Llinás and Miguel Tomé say. If a variety of nervous systems exist in nature, then what plants have is clearly one. Why not call it a nervous system already?

“What do you mean, the flower remembers?” I ask.

It’s 2019, and I’m walking through the Berlin Botanic Garden with Tilo Henning, a plant researcher. Henning shakes his head and laughs. He doesn’t know. No one does. But yes, he says, he and his colleague Maximilian Weigend, the director of a botanical garden in Bonn, have observed the ability of Nasa poissoniana—a plant in the flowering Loasaceae family that grows in the Peruvian Andes—to store and recall information.

The pair noticed that the multicolor starburst-shaped flowers were raising their stamen, or fertilizing organs, shortly before a pollinator arrived, as if they could predict the future. The researchers set up an experiment and found that the plant in fact seemed to be learning from experience. These flowers, Henning and Weigend found, could “remember” the time intervals between bee visits, and anticipate the time their next pollinator was likely to arrive. If the interval between bee visits changed, the plant might actually adjust the timing of its stamen display to line up with the new schedule.

In a 2019 paper, Henning and Weigend call Nasa poissoniana’s behavior “intelligent,” the word still appearing in quotation marks. I want to know what Henning really thinks. Are plants intelligent? Does he see the flower’s apparent ability to remember as a hallmark of consciousness? Or does he think of the plant as an unconscious robot with a preprogrammed suite of responses?

Henning shakes off my question the first two times I ask it. But the third time, he stops walking and turns to answer. The dissenting papers, he says, are all focused on the lack of brains—no brains, they claim, means no intelligence.

“Plants don’t have these structures, obviously,” Henning says. “But look at what they do. I mean, they take information from the outside world. They process. They make decisions. And they perform. They take everything into account, and they transform it into a reaction. And this, to me, is the basic definition of intelligence. That’s not just automatism. There might be some automatic things, like going toward light. But this is not the case here. It’s not automatic.”

Where Nasa poissoniana’s “memories” could possibly be stored is still a mystery. “Maybe we are just not able to see these structures,” Henning tells me. “Maybe they are so spread all over the body of the plant that there isn’t a single structure. Maybe that’s their trick. Maybe it’s the whole organism.”

It’s humbling to remember that plants are a kingdom of life entirely their own, the product of riotous evolutionary innovation that took a turn away from our branch of life when we were both barely motile, single-celled creatures floating in the prehistoric ocean. We couldn’t be more biologically different. And yet plants’ patterns and rhythms have resonances with ours—just look at the information moving through Gilroy’s glowing specimens.

Mysteries abide, of course. We are far from understanding the extent of “memory” in plants. We have a few clues and fewer answers, and so many more experiments still to try.

This article was adapted from Zoë Schlanger’s new book, The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth. It appears in the June 2024 print edition with the headline “The Mysteries of Plant ‘Intelligence.’”

My father collects 100-year-old magazines about Palestine—Life, National Geographic, even The Illustrated London News, the world’s first graphic weekly news magazine. For years, he would talk about these mysterious documents but rarely show them to anyone. “I have proof,” he would say, “that Palestine exists.”

His father, my paternal grandfather, whom I called Siddi, had a similar compulsion to prove his heritage, though it manifested differently. Siddi used to randomly recite his family tree to my father when he was a child. As if answering a question that had not been asked, he would recount those who came before him: “First there was Hassan,” he would say in his thick Arabic accent, “and then there was Simri.” Following fathers and sons down the line of paternity, in a rhythm much like that of a prayer, he told the story of 11 generations. Every generation until my father’s was born and raised in Ramallah, Palestine.

After 1948, however, almost our entire family in Ramallah moved to the San Francisco Bay Area. Although my American-born father didn’t inherit Siddi’s habit of reciting his family tree, he did recite facts; he lectured me about Palestine ad nauseam in my youth, although he had not yet visited. Similar to his father’s, these speeches were unprompted. “Your Siddi only had one business partner his entire life,” he would say for the hundredth time. “And that business partner was a rabbi. Palestinians are getting pitted against the Jews because it’s convenient, but it’s not the truth.”

His lectures were tedious, repetitive, and often fueled with so much passion that they overwhelmed me into silence. And yet they took up permanent residence in my brain, and I would reach for them when pressed to give political opinions after new acquaintances found out I was Palestinian. “So what do the Palestinians even want?” a co-worker’s husband once asked me as we waited in line for the bar at my company’s holiday party. I said what I imagined my father would have said in the face of such dismissiveness: “The right to live on their land in peace.”

But sometime after the luster of young adulthood wore off, I found my piecemeal understanding of Palestinian history—what I’d gleaned from passively listening to my father—no longer sufficient when navigating these conversations. When a man I was on a date with learned where my olive skin and dark hair came from, he told me that Palestinians “were invented,” even though I was sitting right in front of him, sharing a bowl of guacamole. I left furious, mostly at myself. I had nothing thoughtful to say to prove otherwise.

Like my father, I started collecting my own box of scraps about Palestine, although I couldn’t have said why. Perhaps I wanted to slice through a conversation just as others had sliced through my existence, but not even this was clear to me yet. Magazines, books, old posters, and stickers found a home in a corner of my bedroom. My collecting was an obsession. I’d buy books by Edward Said, Mahmoud Darwish, and Mourid Barghouti, not necessarily because I knew who these men were at the time, but because the word Palestine was right there, embossed on the cover.

At first I didn’t dare open these books. They became an homage to my identity that I both eagerly honored and wanted to ignore. My eventual engagement with the material was slow, deliberate. I wanted to preserve a semblance of ease that I feared I would lose once I learned more about my people’s history. I bookmarked articles on Palestine in my browser, creating a haphazard folder of links that included infographics on Palestine’s olive-oil industry, news clippings about the latest Israeli laws that discriminated against Palestinians, and articles on JSTOR with provocative titles like “Myths About Palestinians.” I was building an archive as if I were putting together an earthquake kit—like the ones my parents kept in our basement in San Francisco—even though I didn’t know when this particular survival kit would be useful or necessary.  

But my father knew. His father knew. Our liberation may eventually hang on these various archives.

Even more true: These archives validate Palestinians’ existence.  

In the 19th century, before a wave of European Jews settled in Palestine following the Holocaust, early Zionists leaned on the mythology that the land was empty and barren. The movement advocated for the return of Jews to their ancestral homeland. In 1901, the Zionist author Israel Zangwill wrote in the British monthly periodical The New Liberal Review that Palestine was “a country without people; the Jews are a people without a country.”

In 1969, Israeli Prime Minister Golda Meir was quoted in The Sunday Times of London: “[There is] no such thing as Palestinians … It was not as though there was a Palestinian people in Palestine considering itself as a Palestinian people and we came and threw them out and took their country away from them. They did not exist.” This idea has been similarly reused for more than a century, evolving very little. As recently as February 2024, Israeli Minister of Settlement and National Missions Orit Strock repeated the sentiment during a meeting of Israel’s Parliament, saying, “There is no such thing as a Palestinian people.”

But this fiction of Palestinians’ nonexistence feels tired. It’s a distraction that not only invalidates us but also places Palestinians on the defensive while Israel’s government builds walls and expands illegal settlements that separate Israelis from their very real Palestinian neighbors.

It feels especially absurd in the face of Israel’s latest military campaign in Gaza, launched in response to Hamas’s attacks on October 7. Since then, Israeli strikes have killed more than 34,000 people, according to Gaza’s Ministry of Health, although that number is incomplete. It does not include all of the civilians who have died from hunger, disease, or lack of medical treatment. If Palestinians don’t exist, then who is dying? I fear that Strock’s words may become true, that Palestinians soon will not exist, that slowly they will become extinct. It’s a cruel self-fulfilling prophecy—claim that Palestinians were never there, and do away with them when they continue to prove otherwise.

While listening to my father’s monologues, I used to think about how exhausting it must be for him to keep reminding himself that the place where his father was born is real. At the time, I didn’t think about my place in this heartbreak. But I can’t ignore that heartbreak any longer.

Since October, I’ve returned to my own little box on Palestine. I used to think that this haphazard archive lacked direction, but I see it differently now. This collection proves to me that the place where my great-grandfather owned orchards and grew oranges was real, that the land Siddi was forced to leave behind was a blooming desert before others claimed its harvest. It’s also a catalog of my own awakening, a coming to terms with a history that I didn’t want to know. My ignorance is shattered over and over again when I look through this box and think about all that we are losing today.

Gaza is considered one of the oldest continuously inhabited areas in the world; some of its monuments date back to Byzantine, Greek, and Islamic times. Since the October 7 attacks, however, Israel’s air raids on Gaza have demolished or damaged roughly 200 historical sites, including libraries, hundreds of mosques, a harbor dating back to 800 B.C.E., and one of the oldest Christian monasteries in the world. In December, an Israeli strike destroyed the Omari Mosque, the oldest and largest mosque in Gaza City, which housed dozens of rare ancient manuscripts. Israeli strikes have endangered Gaza’s remaining Christian population, considered one of the oldest in the world, and have destroyed every university while killing more than 90 prominent academics.

The destruction of cultural heritage is not new in the history of war. Perhaps that’s why when my father came across a tattered hardcover titled Village Life in Palestine, a detailed account of life in the Holy Land in the late 1800s, in a used-book store in Cork, Ireland, he immediately purchased it. He knew that books like these were sacred artifacts that hold a truth—a proof of existence outside political narratives. My father’s copy was printed by the London publishing company Longmans, Green, and Co. in 1905. The first few pages of the book contain a library record and a stamp that reads CANCELLED. Below is another stamp with the date: March 9, 1948. I’m not sure if that date—mere months before the creation of Israel—signifies when it was pulled out of circulation, or the last time it was checked out. But the word cancelled feels purposeful. It feels like another act of erasure, a link between my father’s collection and the growing list of historical sites in Gaza now destroyed. We are losing our history and, with that, the very record of those who came before us.

After I started my own collection on Palestine, my father entrusted me with some of his scanned copies of Life that mention Palestine. He waited to show them to me, as if passing on an heirloom. Perhaps he wanted to be sure I was ready or that I could do something with them. One of the magazines dates back to May 10, 1948, four days before the creation of Israel. There’s a headline that reads, “The Captured Port of Haifa Is Key to the Jews’ Strategy.” The author goes on to write that the port “improved Jews’ strategic position in Palestine. It gave them complete control of a long coastal strip south to Tel Aviv … They could look forward to shipments of heavy military equipment from their busy supporters abroad.” Right next to this text is a picture of Palestinian refugees with the caption “Arab Refugees, crammed aboard a British lighter in the harbor at Haifa, wait to be ferried across the bay to the Arab-held city of Acre. They were permitted to take what possessions they could but were stripped of all weapons.”

I can’t help but feel the echo of this history today. I think about President Joe Biden’s plans to build a temporary port in Gaza to allow humanitarian aid in, even though about 7,000 aid trucks stand ready in Egypt’s North Sinai province. Back in October, Israeli Prime Minister Benjamin Netanyahu appeared to welcome the idea of letting help arrive by sea,which at first confused me because not only has he denied that Palestinians are starving, but his government has also been accused by the United Nations and other humanitarian groups of blocking aid trucks from entering Gaza (a claim that Israel denies). Nevertheless, the historical echo seems quite clear to me now as I look through my father’s magazine and see refugees leaving by port 75 years earlier.

I believe my father didn’t want to be alone in his recordkeeping. Who would? It’s endlessly depressing to have to write yourself and your people into existence. But writing about Palestine no longer feels like a choice. It feels like a compulsion. It’s the same drive that I imagine led Siddi to recite his family tree over and over, a self-preservation method that reminded him, just as much as it reminded his young son, of where they came from. It’s the same compulsion that inspires my father to collect the rubble of history and build a library from it.

This impulse is reactive, yes, a response to the repeated denial of Palestine’s existence, but it’s also an act of faith—faith that one day all of this work will be useful, will finally be put on display as part of a new archive that corrects a systematically denied history. Sometimes I hear my father say that his magazines and books will one day be in a museum about Palestine.

“Your brother will open one, and these will be there,” he muses to himself.

Just as the compulsion to archive is contagious, so is hope. Since I’ve started publishing articles and essays about Palestine, I’ve had close and distant relatives reach out to me and offer to share pieces from their own collections.

They ship me large boxes of books and newspapers, packed up from the recesses of their parents’ homes. “Can you do something with these?” they ask. My answer is always yes. I’m realizing that this archiving is not only work I have to do, but something I get to do.

In the middle of the night, my father sends me subjectless emails with links to articles or scanned copies of magazines about Palestine that he’s been waiting to show to someone, anyone, who will care. I save each email in a folder in my Gmail account labeled “Palestine”—a digital version of the box in my bedroom, an archive that I return to whenever I feel despair.

“It’s all here,” my father writes. “We existed. We were there.”