The Intelligent, Ingenious, Utterly Amazing Slime Mold

A veiny yellow plasmodium of a Physarum slime mold, or myxomycete, crawling and moving on a substrate

Things used to be simple. There were two kingdoms, plant and animal, and one kind of real intelligence—human. Then we discovered that Life is creative and complex… Enter the brilliant slime mold.

Every now and then a new scientific discovery is made that is so exciting, so paradigm-shifting, that we need to share it as widely as possible; to think about it; discuss it, absorb it into a new world view of the nature of Life. The good news—it is a worldview that, if we adopt it, will help with our environmental crises. It is so amazing it can’t help but foster respect and wonder for all life.

As a little girl I was fascinated by slime molds. There were these greenish-brownish slimy mushroomy-type blobs in our backyard—that moved! A plant—that moved! After creeping across the yard ever so slowly for a couple of days they solidified into pale pink formless blobs with the feel and look of dry sand stuck together. From movement, into something inanimate. How did that happen??? Later I learned that it had transformed into structure that housed spores—which is what plants do, but not animals.

I would crawl around the yard in hopes of finding one. They were windows into the world between worlds, neither plant nor animal. Our current state of knowledge suggests that they evolved from bacteria and represent the intermediate step in the evolution of the other three kingdoms, fungi, plants and animals. Plants that are on their way to becoming animals? What does that do to our current accepted sense of boundaries between species? Add to that the fact that carrots share 50% of our DNA, and we get totally bolloxed.

And even more mind blowing—slime molds are one-celled organisms without a brain or nervous system, but they have an amazing intelligence. How can that be? Intelligence without a nervous system! They can solve mazes, are capable of learning and remembering, and are able to solve certain mapping dilemmas that even the most advanced computer simulations can’t quite crack. Slime molds are also able to accurately imitate the development of Roman roads dating back to the 1st century BCE.

What does this all mean?? Perhaps that Life itself has intelligence. And when you think about it, it has to. How else could each species adapt and survive, each life form developing its own type of intelligence and its own unique biological pathways to achieve it. (See The Intelligence of Crows and Magpies) Maybe intelligence is a property of Life itself, in myriad, fantastically wondrous expressions.

In one of many experiments, researchers set up little bridges between a slime mold called Physarum polycephalum and an oatmeal treat. Normally the slime mold would bunch together and move across the bridge. Then, the scientists coated the bridges with caffeine or quinine, bitter substances that the organism generally avoids, but which aren’t harmful in small quantities. During the first runs it stopped the slime in its tracks. But apparently it really likes oatmeal so it found a way. It “tip-toed,” extending a long thin tendril of itself across and then speedily moving the rest of its body over the bitter bridge. In subsequent runs it moved ever faster over the bridge and towards the food. Learning that these substances weren’t actually harmful, after about a week they moved across the bridges as if they had nothing on them. When quinine and caffeine were removed from the bridge, the slime mold went back to its original behavior of crossing the bridge with no hesitation. When the scientists changed the substance the slime mold reacted as if it were new, and then learned again that it wasn’t necessary to avoid it.

One of the researchers, Romain Boisseau, explained that basic learning requires at least three steps: a behavioral response to whatever the trigger is, memory of that moment, and future changed behavior based on the memory. Then the organism must be able to “recover” from the process, so it is not locked into the new behavior. The slime mold is learning.

Thus learning likely even predates the emergence of nervous systems, much less brains.We don’t understand how an organism without nerves can do all this. Some theorize that perhaps they can switch genes on or off to potentially store past experiences in cells, allowing organisms without nervous systems to remember and learn. If so – what might that mean about the capacities for all cells to remember, including our own?

“We used to think learning was very complicated, and required a lot of neurons and a brain. But if it is happening at the level of one cell, the process called learning that we thought was complex, might happen through a simple mechanism that could have evolved very early in life. It could be more universal than we realize,” said Boisseau in Proceedings of the Royal Society .

Researcher Chris Reid at the University of Sydney found that, “foraging slime molds leave a chemical trail to avoid retracing their steps. They found a way to externalize spatial memory, allowing them to achieve tasks that would tax the nervous system of far more sophisticated creatures.” Life, apparently, has its ways.

They also have an intuitive understanding of efficiency. Scientists in Japan placed them on a “map” with clusters of food positioned in the place of Tokyo and its suburbs. The slime molds moved to form a network that was startlingly similar to the city’s actual railway system. They did the same with a map of the highways of the United Kingdom. “If some countries started to build highways from scratch I would recommend to them to follow the slime mold routes, “ said Andrew Adamatzky of the University of West England.

Researchers in Japan are exploring the slime molds’ unusual information-processing abilities, and have demonstrated that it has potential use in designing urban transportation systems, or even as logic circuits in bio-computers modeled after the human brain. As one commented, “the future, apparently belongs to slime…”

The implications here are mind-bending and wonderful. A plant-animal. Intelligence without a nervous system. A “blob” with the persistence to cross a noxious bridge to get a treat, once it determined it was safe. A single cell gathering together into a multicelled organism when needed, and successfully cooperating. A blob that can compete with a human brain and a computer in areas that are relevant to its survival. What else is there to discover yet about Life! What a joy to be alive to do so!

Addendum: Walking in a field or a yard,  seeing a blob of something on the ground, would probably not catch our attention. But if we start to attend;  to question, as with the slime mold, we open a doorway into absolute wonder. And the most amazing thing is, this is true for any aspect of life at all, from tiny and inconspicuous to something as huge as a blue whale or the fact that we are made of stardust. Pick a leaf and cut it open – there is an entire multispecies community in there making the leaf work. The chloroplasts that give plants the ability to photosynthesize,- the basis of our life, were once free and independent beings. What happened and how? Plants can communicate in ways we never thought possible, and are active participants in their own fate. It goes on and on. Something else wonderful happens when we attend – we are brought out of ourselves and our personal concerns,  into the larger world of Life and this calms us as well as opening new possibilities for seeing our or the world’s problems in a different light. The whole thing, is only good.  

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