Intelligence in Nature - Jeremy Narby [36]
Trewavas knew that human neurons also use internal calcium elevation when they relay information. Once he saw the speed of the plantsâ reaction to touch, he started thinking about intelligence. Plants may not have neurons, but their cells use a similar signaling system, he told himself, so they may have the capacity to compute and make decisions.
As I listened to him, I realized that he had firsthand experience of the changes that had swept across contemporary biology in recent decades. He had opened himself to the idea of intelligence in nature. This was a courageous step for a Western scientist. I knew indigenous people in the Amazon who consider it a matter of course that plants have intelligence. But in Western cultures, those who attribute intelligence to plants have long been the objects of ridicule. Until now, scientists, and in particular botanists, had avoided using the words plant intelligence. I wanted to know more about how his thinking had changed and pressed him for details.
Gesturing at the documents piled around his office, he said he had read up on a number of different subjects over decades. He described his work method in some detail. âThe family used to complain that I would sit in a chair vacantly thinking. I found it very necessary to do. The ideas donât just come by reading. You have to go away, lie down, sit down, walk about, and let things turn over in your mind. And what I find particularly enjoyable is a problem Iâm trying to solve in my own mind. Is there something I can connect together? And I find itâs only by long periods of doing nothing but think that suddenly facts start coming into your mind. And they come together in an interesting combination which enables you to see the possibilities for what plants can actually do.â He said the notion of plant intelligence had come to him in this fashion. Intelligence in general was a subject that had interested him for years. So when he saw the connection between plants and calcium, it inevitably led him to think about intelligence.
Trewavasâs intuition about calciumâs role in learning in both animals and plants was confirmed by subsequent research. Scientists recently discovered that when an animal learns to avoid a threat, charged atoms of calcium and specific molecules including enzymes are unleashed inside its neurons. They set about modifying the molecular structure of the channels that span the neuronsâ outer membranes and control the import and export of charged atoms and molecules. If the threat to the animal persists, its neurons go on to produce proteins that build new connections, or synapses, between neurons. Along with changes in the strength of existing connections, these new synapses give rise to memory, and allow the animal to remember the threat and avoid it.
An analogous process occurs in plants. When a plant is threatened, by lack of water, for example, exactly the same atoms and molecules are unleashed inside its cells. And they set off the same reactions, first modifying the same import-export channels, then stimulating the production of proteins if the threat persists. Eventually, the plant modifies its cells and their behavior so that its leaves get smaller, its shoots cease to grow, and its roots extend. These responses minimize further stress and injury to the plant. They also take into account external factors such as nutrients and temperature, as well as the plantâs age and previous history.
Science now indicates that plants, like animals and humans, can learn about the world around them and use cellular mechanisms similar to those we rely on. Plants learn, remember, and decide, without brains.
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WE HAD BEEN TALKING for an hour and a half. Trewavas invited me to accompany him to the rooftop cafeteria for a cup