It’s Life, Jim, But How Do We Know It?

What does “life” mean? Hold on, now, I’m not talking about the “meaning of life.” We all know that’s forty-two, anyway. No, the question that I’m getting at is how do we know that something is alive? And no, at no point in this discussion beyond this sentence will I raise the topic of abortion.

I ask the question because I watched an episode of The Universe on Netflix last night. For those of you who aren’t familiar with that program, it’s the History Channel’s attempt to present space sciences to the masses. Occasionally, it does let slip some deep thoughts, and the pictures and animations are well done. The episode that I watched was on the subject of astrobiology. As a writer of science fiction, among other kinds of writing, this is important to me.

So here again is the question: What is life? In what follows, I’ll propose a possible definition. See what you think.

1. A living organism must reduce local entropy.

Entropy, or the second law of thermodynamics, is the observation that in a closed system, energy states must run to the lowest possible level over time. Put another way, the flow always runs from organized to disorganized. (See my desk for an example.) In an internal combustion engine, for example, the fuel, which exists at a relatively high state of potential energy, is burned. That does work, but the products of combustion now are at a lower level of potential energy than before. The universe is likely a closed system, but since it started out at a high state of energy, it has a long time to run down. Earth is not a closed system, speaking in the local sense, because the Sun provides lots of new energy. Some life instead uses geothermal energy of volcanic vents on the sea floor.

Now that you see what entropy is, consider my requirement for life. A living organism must use energy from the environment to create something more complex than its surroundings. Yes, cells eat each other, but what they produce–more of themselves–is still at a higher level of organization than minerals, atmospheric gases, and the like.

I raise this qualification to answer whether fire is alive. Yes, fire consumes food and reproduces, but what it leaves behind is less organized–at a higher state of entropy–than what was there before.

2. A living organism must create discrete units.

Is a rock crystal alive? It reproduces, and its structure is often more complex than its surroundings, but a crystal is a repetition of a relatively simple pattern. Cells, by contrast, have discrete boundaries and internal parts. Some parts absorb nutrients; some contain the genetic instructions for building and reproducing the cell, and so forth. It’s interesting to speculate as to whether a crystal could develop in that manner, but for now, what we know of them says that they are mere repetitions of an organized, but simple pattern.

3. A living organism must have the capacity to reproduce.

Is our Sun alive? In some ways, it acts like a living cell, but it can’t make more of itself. By reproduction, I mean the ability to pass on the form of the living organism through a set of instructions that will assemble a new organism that is separate from the parent. Life on Earth does this through DNA. Making more of something through accumulation–such as what happened in the formation of the solar system when small rocky bodies collided and joined to form planets–isn’t reproduction in this sense.

4. A living organism must be self-contained in its functions.

Yes, living things have to have external sources of energy to live. We all must eat. But the functions of building, repairing, and reproducing the organism have to be contained within the organism.

Is an assembly line alive, for example? It takes in parts–call them food sources–and assembles them into something more complex. But an assembly line doesn’t contain all of its functions within itself. It’s made up of the cooperative efforts of smaller units, the workers. There certainly is a level of analogy here, and the definition gets strained when we consider that multicellular organisms are something like assembly lines. I’m not happy with this part of the definition, even though I have the feeling that I know what it means. This item remains to be made rigorous.

I do want this item, though, because we have to consider whether viruses are alive. A virus is a string of RNA that takes over the machinery of a cell to make more viruses. If the virus is alive, it is only alive in a derivative sense.

What this all means:

You may be wondering why I don’t simply say that a living organism has DNA. The answer is that we may come on something that looks alive on another planet that does not use our method of encoding instructions for life functions. Consider again a crystal that is complex enough to have differentiation of parts and that does more than just copy its structure ad infinitum. Can it be alive?

Or what about computer viruses, worms, and the like? When do they reach a level that qualifies them as being alive? There’s a lot of discussion about what is required for machine intelligence, but if computers gain the ability to assemble themselves, won’t they be a kind of life?

I hot that this isn’t going to be like pornography: We may not be able to define life in a rigorous sense, but we’ll know it when we see it. But even loose definitions can work as guides.

Feel free to offer suggestions for improvement in the definition or alternative ways to define the idea.

By Design

I was raised in a community that demanded belief in creationism.  Seventh-day Adventist doctrine was that the Earth is 6,000 years old and all kinds of living beings were separately created by God.  My problem was that I read too much as a child, and I saw how such a belief has no basis in evidence.

These days, I spend little time paying attention to creationism, other than reading and commenting on the posts of The Sensuous Curmudgeon.  (See the Blogroll to the right and down.)  But one of my students in my Composition I class wanted to write an argument paper on why evolution by natural selection is wrong, and this woke up my memories of doing battle on the side of Darwin.  (I was once labelled the most dangerous person on campus by an Adventist theology professor.)

The present version of creationism is called Intelligent Design.  The argument is that life is both too complex and too well structured to have come about by chance.  There is much that is wrong with such thinking, but for the purposes of this article, let’s consider just the idea that a human being is well designed.

As an analogy, think about a skyscraper.  If you were going to build one, how would you design the support columns?  For a rectangular building, you’d put them at the four corners, no?  Or perhaps you’d put one column in the center.  That second option would work better if the tower needs to be flexible.  A stable structure, though, would not have the main column off to one side with the floors extending away from it.

If human beings are intelligently designed, I have to ask why our spine is placed where it is.  For those of us to whom good nutrition has given some length of bone (as Dr. Lecter put it), height equals back pain.  After standing at the kitchen sink washing dishes or raking leaves in the yard, I want to ask my supposed designer why the human body is so poorly assembled.

The answer, of course, is that our distant ancestors went about on four legs, and a spine at the top, a ridge with rafters coming down, makes good sense.  Watch how stable and flexible a dog or a cat is.  Natural selection, though, operates within boundaries.  A special designer should have made a new blueprint for a new creature, the upright animal, but the rules of biology require working with what is available.  We don’t see something entirely new without antecedents popping up in nature.

Now why am I worrying over this subject?  After all, I’m a writer and English teacher.

For one, I’ve insisted that my students have to meet three conditions in writing their argument essays.  The subject must be 1)  Controversial, 2)  Reasonable, and 3)  Important.  Creationism fails on the second one.  Believing in it is a matter of faith alone, and faith is not something that can be argued reasonably.  Some have a hard time seeing the distinction, but it is a valuable lesson.

But there is another point to make here.  Think about science fiction aliens.  They are often well designed, either as perfect monsters or improved humans.  Vulcans, for example, live somewhat longer, are a bit stronger, have special mental powers, and don’t get eaten by gas clouds with a taste for iron in the blood.  (They also only get to have sex once every seven years, so there are trade-offs.)  The Alien in the movie of the same name had corrosive goo, lots of teeth and an extra mouth, and a nifty bone structure.  It was purpose built to show off Sigourney Weaver”s interesting features.

The problem that I’m addressing is how science fiction writers have a tendency to be intelligent designers.  I’ve faced this myself in writing one of my s.f. novels.  Alien life will have evolved on a different planet and must not look like tweaked Earthers.  At the same time, aliens have to be products of a possible set of mutations and descents.  In other words, they can’t be perfect.

That isn’t easy to do.  Tolkien spent decades constructing the cultures of Middle Earth and got believable results.  Many writers don’t take that much time.  Perhaps that’s why John W. Campbell told Isaac Asimov not to write about aliens.