If you sometimes look around and ask yourself, "So what is life, anyway?"--even if you haven't ingested some illegal substance--you may be interested in a story I've written for Seed magazine. "The Meaning of Life" is the cover story for the August issue, which just turned up at my doorstep. The story isn't online yet, but when it does pop up, I'll make a note of it.
The idea for the story crystallized during the course of my work on my next book. My initial idea for the book was to investigate this very question, "What is life?" There is actually a lot of new research and thinking going into this ancient puzzle. But I recognized that I probably would not come out of such a vast enterprise alive, or at least with my wits intact. So I narrowed the question as tightly as I could, to one species--E. coli. And even under such tight constraints, I wonder from time to time how much of my wits has (have?) survived the experience.
The question "What is Life?" is not purely a scientific question. It helps to think about it philosophically. What I particularly enjoyed in my first experience writing unbloggily for Seed was that the folks at the magazine were not scared off by the thought of an article that tried to look at both biology and philosophy. Whether I've succeeded I'll let others judge. I don't want to give away the goods on the story and spoil the surprise, but if you finish the story and want to learn more, check out the work of Carol Cleland of the University of Colorado, NASA's philosopher-in-residence. Here's the Google scholar page for one of her key papers, "Defining 'Life.'"
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It's simple, Carl:
Life is a self-assembled system that exploits a loophole in the second law of thermodynamics, which states that the entropy of a closed system must always increase� on average.
Living organisms get around this law by accelerating the �flow� of entropy around them and harvesting a portion of the difference between natural flow and accelerated flow to fuel local decrease in entropy. (Net entropy increases.)
I haven't read anything recent on the definition of life, but after reading your evolution book, I believe that one defining quality of life is the ability to pass information to its offspring.
In our recent history, we can see how much culture has evolved just since the creation of language and writing, and how valuable passing information down through that method has been. I think we're seeing the same kind of process that enabled life to begin and evolve.
Hmmm, right off the bat I see, that there is Error in Cleland's article!
If I might just make a comment to the previous comment on defining life based on reporoduction. I think the definition constrains the way we look at life and evolution. By defining that life = something that can reporoduce we get into this circular definition in evolution of saying that the fittest organisms are those that reproduce in the given circumstances.
Why should reproduction be treated as the defining parameter?
Reproduction is simply one of the key parameters in evaluating fitness. In general, since evolution has no 'end goal',the end goal of evolution is certainly not to produce organisms that can reproduce the best! :-)
1 - Erwin Schrodinger, 'What is Life?', 1944 is available on the web.
http://home.att.net/~p.caimi/schrodinger.html
I respectfully suggest a subtitle for your version.
2 - I have been thinking about your National Geographic article 'From Fins to Wings, NOVEMBER 2006; specifically the illustrations for evolution of the eye.
Since fauna do not have chloroplasts, but are related to flora as eukaryocytes; it may be possible that chloroplast genes brought into the cell nucleus somehow evolved into eyes as an alternate type of photoreceptor rather than function in photosynthesis?"
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I am not an evolutionary biologist, so I feel naive on the subject "what is life". But several months ago I became enamored of the importance of boundaries and domains in organisms. Cell membranes are the most obvious example, but, in vertebrates there are other larger domains, such as within the CNS, within the gut, and, most obviously, the external surface of the organism (separating self from non-self).
Clearly, boundaries don't define life. soap bubbles aren't alive. But its hard to imagine a living organism without an external boundary. Replicating DNA floating in an ocean doesn't seem like it should be called life. Once it is bounded it seems much closer.
Finally, I'm not sure the definition of life is an interesting or well formulated. Perhaps it is interesting only because intelligent life evolves from non-intelligent life.
Is it not true that definition by its own very definition limit and constrain the possibilities of that being defined?