After googling the definition of Life and I was a bit disappointed to find that the best definitions were anchored in functions we associate with life, but I couldn’t quite put my finger on why this made me sad.
“the condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death.”
Setting aside the use of a word to define itself (in this case “animals and plants” are synonymous with life and “inorganic” is just another way of saying “not living."), all of the things listed here felt like something that could easily be used to describe something that isn’t alive.
What about a fire? I was reminded of this classic example recently while reading a sci-fi book, but subsequently remembered it from high school biology. A fire has the capacity for growth, reproduction, functional activity, and continual change preceding death. So is a fire alive?
I’ve kept this question in the back of my mind for the last couple weeks because I want to find a definition of life that is more in line with my intuition of what life is.
One of my favorite examples of a thing that may not fit a traditional definition of life, but every fiber of my intuition would argue that it should, is Conway’s game of life. The patterns of movement, change and interaction mimic what you might see under a microscope in an environment teaming with life. When left to the imagination, the possibilities that come from running it with enough complexity for enough time seem endless. But it still begs the question, why does such a game scream life, when a fire doesn’t?
What is a fire? Atoms get tied together in ways that are a bit more complex than they prefer, and with a little encouragement, they decide to go their separate ways. Word spreads fast among the atoms and before you know it all the molecules are trading atoms and releasing heat. It is nothing more than a simple chain reaction that starts with molecules bonded together with some energy, and ends with different molecules bonded together with less energy.
How is this similar to life? Well, if you look at non-photosynthetic life, it leverages exothermic reactions in a very similar, though more controlled way. The question is, controlled to what end? Why is it controlled and is this control the thing that differentiates life from a fire?
We often talk about life as the animal, or the plant, but we don’t talk about fire as the hot coal or the flaming leaf. Just how a fire is the process those things undergo, we can think of life as a process, out of which the byproducts are plants, animals, bacteria, etc…
Thinking of life as a process, allows us to compare more closely with fire. We can start by looking at the preconditions, which in the case of life that we’ve found so far, starts with atoms with a good amount of flexibility in comfortable configurations (carbon). This opportunity for complexity is seeded by an environment that is constantly stirring the pot and encouraging that complexity (usually with heat) until it reaches the point where the complexity created can self-encourage. It is a chain reaction, just like the fire, but instead of complexity crumbling away, it is slowly building up with the careful finesse of self-regulation. Instead of the uniform exothermic chain reaction created by the fire, life is a delicate dance of endothermic and exothermic reactions that balance each-other out.
Another thing I like about this definition is that you can take something like cancer, which, if you evaluate it in isolation looks a lot like life, and move it over to have a definition closer to a fire. The very fact of it’s malignancy means it is no longer holding that delicate balance of life.
What about Conway’s game of life? It doesn’t have atoms or molecules, it doesn’t always perform all of the functions listed above, but it does provide a good opportunity for complexity seeded by an environment that can inject just enough complexity to allow the complexity to run away with itself.
Okay, okay, I know what you are thinking. What about crystallization? What about fractals? They are infinitely complex, would you call the process of crystallization life? This is a great question that really requires us to challenge our concept of complexity and think about the true nature of entropy. If we take the equation for a fractal and execute it forever, is it really infinitely complex? Or is it only as complex as the equation? If complexity is patterned, that by definition stops the clock on new complexity. Just like the example of a cancerous tumor, the whole universe could be filled with them, but it still has a pretty low complexity compared with a universe teaming with biodiversity.
Hopefully this made you think a little, it occupied several showers for me and while it probably isn’t original thought, I mostly wouldn’t know because I didn’t start my showers with any research and left out citations from my pontificating because finding them takes time and I’m pretty sure no one reads this blog. If I’m wrong, feel free to have a conversation with me about it, you will at least get to see the surprised look on my face while I process the news that someone is reading the stuff I write.