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What pray tell is life?

On a hypothetical simmering ocean world, under an oversized blue-white star, the tendrils of one of sci-fi writer Steven Baxter’s “Qax” reach out to the limb of another in the distance.

It’s fair to think we know life when we see it. But is that really true? Scientists have worked on defining life for decades, and in most cases they’ve ended up with a pragmatic suite a characteristics that’s both useful and clearly incomplete. With the recent focus on Mars, the effort is rejoined. Here’s one stab at it:

Faye Flam — That’s been a concern for NASA, and so in the 1990s, the space agency convened a panel to try to define life, said Steve Benner, a biologist from the Foundation for Applied Molecular Evolution(Ffame). The panel put evolution front and center: Life, the panel decided, is self-sustaining chemical system capable of Darwinian evolution. Benner said Carl Sagan had some pull on the panel. “This definition is very Saganesque.” …

Some creationists worry that the NASA panel’s definition will force scientists to ignore or cover up findings of life forms that didn’t evolve. Take the creationist website, “Uncommon Descent,” which accused me of “getting it wrong” in a previous column for mentioning NASA’s Darwinian definition without saying it’s controversial because a post-doc at Michigan State University criticized it in a blog post.

The blogging post-doc post in question proposed a “thought” experiment: “Suppose we go to another planet and find one being there, looking exactly like a human being. Everything we can measure about this being confirms that it is just as much alive as you and me. It eats, moves, heals, replenishes, communicates, feels, defecates. Learning more about this being, though, we find that it has no ancestors, and that it does not age. It does not reproduce, and it is the only such being on the planet. Thus, there is no lineage of descent and no population that can evolve. So this being is then not alive? Of course it is. This definition does not work.”

The article notes there’s a subtle semantic difference at work here, between living and life. That being said, is it a good idea to limit our definition to chemical systems that evolve?

It certainly make sense given the facts we have to work with here on earth! Maybe chemistry is the only way replicating system, using local resources to grow and reproduce, can or has developed in the universe. But should we count out other possibilities?

Comments

  1. fastlane says

    What about digital life? We can create self replicating programs with built in selection and random bit flipping (lots of good info online). What would happen if it somehow managed to get into the ‘hardware’ and start producing more hardware, which would move it from the virtual, to the physical realm, at least. Would we call that life? Mostly unrelated to your post, but there is a lot of good reading on the topic, and since you mentioned creationists anyway…

    I think any life without technology (that we could probably recognize) would be chemical in nature. Is there any other driving mechanism in the universe that we could even imagine at this point that might otherwise develop a living system?

  2. says

    Despite everything else, such a being would most certainly be an artificial life form, even if it’s biological. I would consider it alive, but would categorize it differently than a natural life form. The evolved beings who built it would be interesting to meet.

    But I’m not a biologist, so they may consider it differently.

  3. jamessweet says

    The anonymous “blogging post-doc” referred to is Bjorn Ostman, and I’m sure he would be infuriated to know that his words are being twisted by creationists in support of their agenda!

    I rather liked Bjorn’s thought experiment. I don’t think it completely illegitimizes the Darwinian definition of life (this distinction between “living” and “life” is interesting, but more importantly, Bjorn’s scenario is completely unrealistic and so is probably not a problem in practice for the definition) but it definitely makes us think!

  4. Gregory in Seattle says

    Life:

    Life is the characteristic of objects considered to be alive. Because life is a system of processes and not a discrete substance, it is defined based on a list of descriptive characteristics: to be considered alive, an object must exhibit metabolism, self-organization, reproduction and adaptability.

    I really need to put in more work on that article, but it’s a start.

  5. a miasma of incandescent plasma says

    That’s just weird. “So what if you find a rock that likes Beethoven”… I thought that thought-experiments needed to be plausible.

    And everything comes from something. You’d be able to trace a rock’s atoms to the dead exploded star they were manufactured in, and the path of cosmic evolution it took to get there.

    So yeah, if the universe happens by chance to make a fully functioning person from a similar process that produces an asteroid then we’ll revisit the definition. Until then, I’m going to assume that isn’t going to be done in this universe (but multi-universe theory says it could and probably has happened) and say that chemistry and descent with modification is going to be involved since the law of nature seem to be consistent throughout the universe based on the current available evidence.

  6. says

    “Suppose we go to another planet and find one being there, looking exactly like a human being.

    Suppose 10,000 flying purple monkeys shoot out of my ass. It’s more likely to happen.

  7. jaytheostrich says

    Hmm.. creationist..
    “Suppose we go to another planet and find one being there, looking exactly like a human being. Everything we can measure about this being confirms that it is just as much alive as you and me. It eats, moves, heals, replenishes, communicates, feels, defecates. Learning more about this being, though, we find that it has no ancestors, and that it does not age. It does not reproduce, and it is the only such being on the planet. Thus, there is no lineage of descent and no population that can evolve. So this being is then not alive? Of course it is. This definition does not work.”

    I get it! They think we’ll find Jesus on another planet, and those evil scientists will immediately call Him non-life, kill Him (again) and never tell anyone, cause they hate God. That’s what scientists do, right? Right?

  8. Emptyell says

    @ 6,7,8 Yes!

    …and if I were to fall down a rabbit hole and talk to a vanishing cat, a dormouse and a mad hatter would they also be alive despite no evidence of having evolved?

    If we’re to count that as a thought experiment then all of mythology, literature and superstition qualify as well. It’s more of a philosophical musing. And not a particularly interesting one. I think this barely rises to the level of a deepity.

    My model of what qualifies as thought experiment are Einstein’s examples. Imagining the impossible (traveling at the speed of light) to help understand an actual, measurable phenomena (the speed of light). Since we have no evidence of, and no reason to expect we ever will find evidence of, complex life forms appearing spontaneously, there is nothing informative about this so called thought experiment.

  9. jamessweet says

    I thought that thought-experiments needed to be plausible.

    Um, no, that’s sort of part of the point of them being thought experiments.

    Hmm.. creationist..
    “Suppose we go to another planet and find one being there,

    No no no! The blogger who proposed that thought experiment is NOT a creationist, and I’m a bit annoyed at the otherwise excellent Faye Flam that she portrayed this whole thing in a confusing manner. Bjorn Ostman is the “blogging post-doc” who proposed the thought experiment, he is most certainly not an ally of creationists, in fact he is an excellent evolutionary biologist with god-knows-how-many publications, is an outspoken atheist, a vocal opponent of creationists, and I’m sure would be absolutely mortified to find his thought experiment being wielded in this way.

    As I said earlier, I found his thought experiment very provocative and interesting. Is a definition still valid if it fails to comprehend unrealistic scenarios? I don’t know. If your definition of “bulletproof” is “stops a bullet under any possible set of circumstances”, then I would say that is not a very good definition even if I have to resort to implausible circumstances, like a bullet being fired at the speed of light. A better definition of “bulletproof” would specify the parameters under which a material can stop a bullet, e.g. the limit of caliber, speed, number of rounds fired in the same place in the material, etc. When possible, it’s better to clarify your definition than to just hand wave and say, “Well, I probably won’t get shot by a gun that big anyway, so who cares?”

    Granted, in this case Bjorn has not offered a clearer definition (which he freely admits). I’m still inclined to think that the Darwinian definition is the best we have (barring artificial life, of course), but the thought experiment points out that the definition may have some problems.

  10. Pierce R. Butler says

    jamessweet @ # 3: … Bjorn’s scenario is completely unrealistic …

    As a science fiction scenario, it could be very simple: the humanoid was artificially created by unknown entities who left it there, for purposes the pursuit of which puts the protagonists through a plethora of purple-prosed perils.

  11. says

    Why would we have to limit our definition to the kinds of life observed on Earth? This is NASA we’re talking about!

    On top of that, and as Pierce R. Butler highlights above, are we to exclude as life living organisms that are created? If humans create artificial life, for instance an artificially made cell, then are we not to say that it is alive, and that it is life, just because it is not evolving? That would be hogwash.

    Bjørn Østman

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