(This month’s post features a photo of Stentor coeruleus by Jasper Nance on Flickr. Under a microscope, this little guy looks translucent white, with green and brown bubbles trapped inside of it. It’s roughly cone shaped, rooted to some debris at its narrow base, bent at a ninety degree angle as its wide, cilia-lined mouth quests about for food)
Sometimes I like to talk about all sorts of living things as “intelligent,” even ones that are very simple and reflexive in their behaviors. That’s because I tend to think of the process of evolution itself, and everything it creates, as intelligent. In some sense, I feel like the simplest of creatures are particularly intelligent in their design, because they don’t waste any effort on “thinking” or complexity when they don’t have to. But this isn’t how most people use the word “intelligent,” which is a problem. It’s not a particularly well defined word, either, so I think my view deserves some clarification. How are evolution and cognition related to each other? That’s something I’ve been thinking about a lot lately.
Perhaps it’s best to start with some of the simplest life on the planet: bacteria. They are basically just little robots, controlled by a simple “computer” made out of proteins and genes (here’s a great book on the subject). They certainly don’t “think” like we do, but they do perceive their environment and respond to it appropriately. They seem to have a model of their tiny selves, and their relationship with their environment, that lets them make good decisions from moment to moment, to survive in a hostile world with intermittent food, and many poisons and predators about. They aren’t particularly creative, but their evolved programming can handle a very wide range of contingencies, responding in appropriate ways to just about anything that their ancestors have encountered in the past.
Even very simple computer programs can learn. It’s just a matter of observing when two experiences tend to go together, and recording that association for later. This is all that “AI” is doing, and it can be shockingly effective. There’s no reason that a “computer” made of proteins and genes couldn’t do the same thing. But simple cells like bacteria don’t need to do this. They reproduce so quickly, they can simply evolve instead. The difference is surprisingly subtle. Bacteria use a relatively fixed “program” for themselves. Unlike a mind, it isn’t made to reorganize itself to conform with experiences in the world, it just does what it does. However, this “fixed” program is constantly being subjected to random edits (mutations), so it does change. The main difference is that genes accommodate to the environment by death and survival, rather than learning within a lifetime. Bacteria are incredibly prolific. E. coli can easily fill a single square millimeter with over 10 billion cells, and a population can double in twenty minutes. As long as some of the random edits are good, and they spread quickly, bacteria can adapt in real time to their changing environment, without learning.
What’s interesting is that more complex cells do seem to learn. Animals like you and me are built out of vast numbers of eukaryotic cells, but our ancestors were actually single-celled eukaryotes, and there are still plenty of those thriving out in the wild today. These cells are much larger and more complex than bacteria. In the past, they actually swallowed up other cells, that went on living inside of them. So, they’re actually like little clusters of several cells in one, working together as a team. Thanks to one of these symbiotic partners, mitochondria, eukaryote cells have a much larger energy budget than bacteria. Their genomes also have much more complex structure and regulatory mechanisms. They can actually re-write the instructions in their genes after reading them, using a process called splicing. We’re still not completely sure that these single cells do what we’d call “learning,” because we only recently thought to look for that, and it’s rather difficult to prove definitively. But there’s good reason to suspect they can.
There’s a single-celled eukaryote called Stentor coeruleus that is shaped like a tiny trumpet. It’s actually considered to be huge for a single cell, at a whopping two millimeters long. That may not seem like much, but it’s 1,000 times bigger than an E. coli bacterium. This little guy is very sensitive to vibrations, which it uses to detect predators. When it feels threatened, it contracts into a tiny ball to make itself harder to catch. What’s interesting, though, is that when it feels the same vibration over and over again and doesn’t get eaten, it learns to ignore vibrations at that frequency (but not other frequencies). That learning is flexible, because if the vibrations get stronger (as if the predator were getting closer, perhaps), it can change its mind and go back to treating them as a threat. This sort of behavior is pretty simple, but I would consider it “intelligent” in a minimal sense. It has a non-trivial model of the world that it updates in real time without having to evolve to do it.
As organisms get larger and more complex, they also become slower. They move more slowly and they reproduce more slowly. They also tend to have larger, more complex genomes which are much harder to successfully edit with random mutations. As this happens, life needs to find ways to keep responding quickly, and one solution is to invest more in cognition. Even single celled organisms like Stentor seem to do this. Larger organisms like plants have even more complex cognition. Plants may not seem very intelligent, but they can learn, behave strategically, and even communicate. They interpret clues over a season to guess when it’s safe to grow, they maneuver around obstacles and each other to get access to light, and warn each other when pests show up. This isn’t thoughtful, exactly, but neither is it simply hard-wired. There’s flexibility, context sensitivity, memory. Real, non-trivial computation. More complex organisms, like animals, have even evolved their own specialized “computers” built out of cells: brains. They are much more intelligent than plants, in one sense, because their behavior is so much more flexible and dynamic. They really can think, which for most people seems to be the gold standard for intelligence.
The powerful thing about investing in cognition is that it makes evolution easier. An intelligent organism doesn’t need to evolve exactly the right behavior for a situation, it just needs to be “close enough” from birth that learning can take it the rest of the way. For instance, most animals have to learn how to walk. That means when an animal is born a little different, say with legs that are shorter than usual, it can figure out how to work with that. In fact, if having short legs turns out to be useful, they might do better than their peers, even if they have a body type never seen before in their family history. If a species has to re-learn the same behavior in every generation in order to survive, then natural selection will favor individuals that learn that skill more easily and reliably. For instance, baby deer learn to walk very quickly, seemingly because they are born with some innate clues for how to do this, and an urgent desire to do so. In this way, behaviors that were at first creative solutions to novel problems can slowly become reliable programs encoded in the genes. This sort of dynamic is sometimes called “genetic assimilation” or “the Baldwin Effect,” and it’s one of the key ways that life uses its evolved intelligence to shape the process of evolution to make it more efficient.
This is why I like to think of evolution and cognition as continuous with one another. They are different things, but they are both kinds of learning, just happening on different time scales, and there is flow between them. Flexible cognition can make evolution much easier, and evolution can generate new opportunities for cognition to work with. You might say that organisms like bacteria, which are little more than fully-automated evolved mechanisms, aren’t intelligent because their behaviors are rigid and can’t adapt without evolution. But perhaps an evolving population of bacteria is intelligent? It can be quite flexible and dynamic, adapting to dramatic changes in the environment in minutes. This is why they can be so difficult to control, and often very challenging for our immune system (which is very intelligent and flexible) to keep up with.
Organisms like plants rely a lot on evolved mechanisms, but they also have some minimal real-time learning and flexible behavior, so I would consider even a single plant to be intelligent. Animal species like insects, reptiles, and mammals shift the balance even further toward real-time cognition. In a sense, every organism is precisely as smart as it needs to be to live its lifestyle. If it can be successful and thrive without expensive, complicated, biological computation that can learn in real time, that’s a good “design.” I consider that to be intelligent, even if the organism itself doesn’t seem so intelligent. Every organism evolved from a single common ancestor, and has had just as much time to adapt. Some have become extremely good at being extremely simple, with precisely honed, fully automatic routines controlled by genetics that have stayed stable for hundreds of millions of years. Others have less refined innate behaviors, and make up for it with flexible learning and cognition. Neither option is better, and evolution explores the full range of that spectrum, finding a huge variety of strategies to survive and thrive in a complex world!
Thinking with Nate 