Plant Pantheism

A few years ago I attended a conference where some apparently serious people debated whether plants had consciousness. To me this seemed absurd, given that consciousness is a product of neural systems in general and brains in particular. While I’ve never had any problem attributing consciousness to animals, plants seemed a domain or kingdom too far. Without neural systems or brains, how could they have consciousness? They can’t, at least if we adhere to traditional definitions of consciousness, sentience, and intelligence.

But if we acknowledge, as we must, that plants are living organisms with whom we share a common ancestor going back billions of years, then the notion of asking a Nagel-like question (What is it like to be a plant?) makes good sense. While most of the speakers at the conference I attended were starry-eyed mystics, neo-pagans, and pantheists, one was a harder-nosed scientist. She discussed recent research into plant “behavior” and it sounded fascinating. So I did some skeptical reading in this nascent field and came away impressed. Plants are far more interesting than I had supposed or imagined.

Several studies have shown that plants can recognize and favor kin. Impressive as this is, it’s nothing compared to the possibility that some plants have memory and are capable of learning. While this sounds incredible, check out this excerpt from an article that Michael Pollan just published in the New Yorker:

The most controversial presentation was “Animal-Like Learning in Mimosa Pudica,” an unpublished paper by Monica Gagliano, a thirty-seven-year-old animal ecologist at the University of Western Australia who was working in Mancuso’s lab in Florence. Gagliano, who is tall, with long brown hair parted in the middle, based her experiment on a set of protocols commonly used to test learning in animals. She focussed on an elementary type of learning called “habituation,” in which an experimental subject is taught to ignore an irrelevant stimulus. “Habituation enables an organism to focus on the important information, while filtering out the rubbish,” Gagliano explained to the audience of plant scientists. How long does it take the animal to recognize that a stimulus is “rubbish,” and then how long will it remember what it has learned? Gagliano’s experimental question was bracing: Could the same thing be done with a plant?

Mimosa pudica, also called the “sensitive plant,” is that rare plant species with a behavior so speedy and visible that animals can observe it; the Venus flytrap is another. When the fernlike leaves of the mimosa are touched, they instantly fold up, presumably to frighten insects. The mimosa also collapses its leaves when the plant is dropped or jostled. Gagliano potted fifty-six mimosa plants and rigged a system to drop them from a height of fifteen centimetres every five seconds. Each “training session” involved sixty drops. She reported that some of the mimosas started to reopen their leaves after just four, five, or six drops, as if they had concluded that the stimulus could be safely ignored. “By the end, they were completely open,” Gagliano said to the audience. “They couldn’t care less anymore.”

Was it just fatigue? Apparently not: when the plants were shaken, they again closed up. “ ‘Oh, this is something new,’ ” Gagliano said, imagining these events from the plants’ point of view. “You see, you want to be attuned to something new coming in. Then we went back to the drops, and they didn’t respond.” Gagliano reported that she retested her plants after a week and found that they continued to disregard the drop stimulus, indicating that they “remembered” what they had learned. Even after twenty-eight days, the lesson had not been forgotten. She reminded her colleagues that, in similar experiments with bees, the insects forgot what they had learned after just forty-eight hours. Gagliano concluded by suggesting that “brains and neurons are a sophisticated solution but not a necessary requirement for learning,” and that there is “some unifying mechanism across living systems that can process information and learn.”

This is fascinating stuff, even if it is potentially nightmarish for ethical vegans.

Pollan’s piece, “The Intelligent Plant,” is a superb and comprehensive introduction to this field. It’s long but well worth your time and attention.

Human-plant

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6 thoughts on “Plant Pantheism

  1. Gyrus

    I can accept “scientifically-minded” people’s antipathy to the readiness with which many believe in such things as plant consciousness. However, it seems utterly perplexing that many such people, at the same time, dismiss these things with equal readiness. I know there’s some point to be made in there about the burden of proof etc., but in the end that doesn’t really wash for me. Uncertainty seems more scientific than dismissal or belief.

    There does seem to be a lot of interesting evidence for plant behaviours piling up. In the end, why not consciousness? Are we saying the experience would be the same as ours? No. But what is the actual evidence for consciousness being dependent on brains etc.? OK, in terms of self-consciousness, we can perhaps draw some lines with observable evidence for that, and that may be unique to humans and certain animals. But actual conscious awareness is a phenomenally varied thing. In a culture dominated by Darwinian thinking, it seems odd that his perception of continuum in the natural world is so thoroughly and casually rejected when it comes to consciousness. Odd, until you consider humanism’s inheritance of Christian anthropocentrism.

    BTW, “potentially nightmarish for ethical vegans” – I assume you’re being tongue-in-cheek! Thanks to a few loud and punctilious self-appointed vegan spokespeople, there seems to a silly popular image of veganism as being utterly divorced from sense and pragmatism. This piece was a terribly conceived attack from that viewpoint. It was only a shame that the extent to which it was a straw man attack was clouded a little by the loud vegans in the comments…

  2. Cris Post author

    Uncertainty certainly is more scientific than dismissal or belief. Just this morning I was reading an Edge essay by Paul Saffo, which I will cite in whole:

    The breathtaking advance of scientific discovery has the unknown on the run. Not so long ago, the Creation was 8,000 years old and Heaven hovered a few thousand miles above our heads. Now Earth is 4.5 billion years old and the observable Universe spans 92 billion light years. Pick any scientific field and the story is the same, with new discoveries—and new life-touching wonders—arriving almost daily. Like Pope, we marvel at how hidden Nature is revealed in scientific light.

    Our growing corpus of scientific knowledge evokes Teilhard de Chardin’s arresting metaphor of the noosphere, the growing sphere of human understanding and thought. In our optimism, this sphere is like an expanding bubble of light in the darkness of ignorance.

    Our optimism leads us to focus on the contents of this sphere, but its surface is more important for it is where knowledge ends and mystery begins. As our scientific knowledge expands, contact with the unknown grows as well. The result is not merely that we have mastered more knowledge (the sphere’s volume), but we have encountered an ever-expanding body of previously unimaginable mysteries. A century ago, astronomers wondered whether our galaxy constituted the entire universe; now they tell us we probably live in an archipelago of universes.

    The science establishment justifies its existence with the big idea that it offers answers and ultimately solutions. But privately, every scientist knows that what science really does is discover the profundity of our ignorance. The growing sphere of scientific knowledge is not Pope’s night-dispelling light, but a campfire glow in the gloom of vast mystery. Touting discoveries helps secure finding and gain tenure, put perhaps the time has come to retire discovery as the ultimate measure of scientific progress. Let us measure progress not by what is discovered, but rather by the growing list of mysteries that remind us of how little we really know.

    So I think we agree.

    As for the possibility of plant consciousness, my hesitation is that if we are scientifically inclined (as I like to be) and linguistically minded (as we all are), then we should aspire to basic agreement on terms. We might even begin our conversations with quaint things like non-essentialist definitions (keeping in mind, of course, that language is slippery and definitions are simply shorthand for what Wittgenstein calls “family resemblances”).

    With this in mind, we might like to designate “consciousness” as the product of neurological systems. Brains may or may not be required. Because plants lack neurons, I think we first should be able to show, with some scientific rigor, that they have functional equivalents which give rise to actions that are analogous to neurological consciousness.

    When it comes to plants and functional equivalencies, I would prefer to begin our inquiries with something other than a category or concept called “consciousness.” I think we should begin by describing, in detail, the various properties of plant action. Once we have a good grip on plant action, we might then asking Nagel-like questions about plant “being” and “consciousness.”

    But I think we are a long ways away from having good descriptions of what plants do, so talking about plant “consciousness” may (at this preliminary juncture) curtail our inquiries and limit our imaginations.

  3. Gyrus

    On “functional equivalents” of neurological systems and plant behaviours, I’m sure you’ve read Michael Pollan’s recent New Yorker piece. Some important scientific issues well-covered. There’s also an excellent book by Jeremy Narby, Intelligence in Nature, which covers some very interesting research – especially in Japan, where the animist Shinto backdrop to culture has left science free to explore some areas curtailed by our own monotheist inheritance.

    I agree generally with what you’ve put here. It reminds me of a part of Pollan’s piece that questions the “animal-centric” focus of much “plant intelligence” speculation, i.e. trying to identify “functional equivalents” of the kinds of intelligence-generating apparatus that animals happen to have. This limits us from appreciating radically different kinds of intelligence and power.

    “Why would a plant care about Mozart?” the late ethnobotanist Tim Plowman would reply when asked about the wonders catalogued in The Secret Life of Plants. “And even if it did, why should that impress us? They can eat light, isn’t that enough?”

  4. Larry Stout

    It’s disillusioning to see inference of something transcendent, and somehow comparable to animal brains, where experiment has (so far) failed to explain in physicochemical terms. Neo-animism?

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