I knew I'd love Carl's Microcosm for the delicious irony of using a mere "germ" to illustrate the mysteries of life itself. Well, I'm also partial to bacteria and their multicellular abilities, which Carl describes wonderfully. .
First, as the other science writer on the panel, I'd like to express my appreciation for Carl's way with a metaphor. I think for many of us, what makes science writing take flight are these wonderfully unexpected yet perfect comparisons that convey understanding along with a flash of sensory fireworks. For instance, Carl describes a (eukaryotic) cell's stained chromosomes as looking like "crumpled striped socks." Perfect! They really do. Another literary allusion made me laugh out loud. But I hesitate to give away for risk of spoiling its effect for those who haven't read the book yet. It comes at the end of the first graph on page 21. My daughter, a Shakespeare fanatic, will love it.
Well, I'm posting from a VERY SLOW dial-up connection from a remote cabin off the coast of British Columbia. Friday I'll catch a ride up island to the radio-connected Internet Center to post more. Till then, I'll wrap up this plain post with a question for Carl. It's an old question, I know. But since Carl's book centers around "what is life?" I get to indulge my obsession with it.
Carl, twice in the book you refer to viruses as "creatures." Perhaps you used the word metaphorically. In any case I'd love to know whether you think viruses qualify as being alive, and I'd love to hear your reasoning either way.
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Personally I define life as entities amenable to evolution by means of natural selection. As such, viruses fit this definition. See more here: http://tinyurl.com/3ryxar and here: http://tinyurl.com/66nskh
That is exactly the same question I was pondering while reading that the inspiration for the book was the question: "What does it mean to be alive?"
Living in Ecuador, I think I'll have to wait a few months until I can get a hold of a copy of the book, but I'm extremely curious as to what Carl Zimmer's definition of life is, when compared to, say, Martin Mahner and Mario Bunge's take on how to define life.
I'd love to hear some of the contributor's thoughts on this topic as well.
I don't remember Carl making an explicit definition of life in the book (Correct me if I'm wrong).
In my opinion, viruses ARE alive. My definition of life includes all entities that evolve by natural selection. I've blogged about this here http://tinyurl.com/3ryxar and here http://tinyurl.com/66nskh.
As one astute observer commented, "I'm going with Nobelist Nebraskan George Beadle: 'Is such a virus living? The question is unanswerable without a definition of 'life.' And any definition of life must be arbitrary.' (1964, quoted in PATOOMB)"
Note: PATOOMB is the acronym for the book Phage and the Origins of Molecular Biology.
When I started graduate work 11 years ago, I was taught that viruses are not living things. Period.
However, I see more and more references to them as live organisms. I think it might be a little like 'data' as plural versus singular. There may have been a correct answer before, but now both are accepted.
I guess it really comes down to your personal belief about what constitutes life. In my world, viruses are alive.
"Life" is blurry in the same way that "species" is, never mind the ambiguous nature of the concept itself which Mahner and Bunge touches.
Presumably astrobiology will need one some day, meanwhile they contribute for example the so called NASA definition of life, roughly "Life is a self-sustained chemical system capable of evolution".
I loosen the requirements further and note that as evolution is the process of life, it defines life as a process on populations, roughly "Evolution is a process that results in heritable changes in a population over time". And consider biological populations undergoing such a process as life we are interested in.
Personally, I think simplified parasites qualify, even extreme cases such as viruses. These would qualify under an evolutionary based definition of organism by Rybicki et al:
YMMV. Evidently prions can't be pressed into such definitions. The "genetic material" is the topology, but that isn't the problem. IIRC a biologist claimed on a blog that prions are "dirty" assemblages without faithful reproduction.
When I started graduate work 11 years ago, I was taught that viruses are not living things. Period.
However, I see more and more references to them as live organisms. I think it might be a little like 'data' as plural versus singular. There may have been a correct answer before, but now both are accepted.
I guess it really comes down to your personal belief about what constitutes life. In my world, viruses are alive.