A tossup between here and GQ.
What defines life? What quality or behavior is exhibited by something so that we call that thing alive if this behavior occurs, and call it dead if it does not?
I would prefer to keep this away from the potentially inflammatory question of “When does life begin?”, because I am talking about any sort of life, and I believe that most of us would refer to sperm and eggs as alive, even when they are separate.
Life has certain characteristics, some of which include:
Consumption/Excretion
Reproduction
Growth
Death
There are of course exceptions to every rule: Some trees never seem to die naturally (old age as opposed to, say, a fire or an axe). Some life-forms never seem to grow, such as viruses. And reproduction… I could go on all night, there are so many positions one can take!
And even that has its exceptions: Is a virus really alive? What about fire?
In my opinion, the Star-Trek-style “Lifeform Detector” is a crock. There isn’t one aspect you can point to and say “THAT means this is alive”. It takes careful study and extensive debate.
Og help the first person to discover silicon-based ‘life’!
…or, of course, zombies.
Wow Plynck, you don’t mess around, do you? They don’t come much stickier than this.
Personally, I prefer to keep the list of requisite qualities simple: it has to take in energy (in some form, doesn’t matter how), and reproduce. By “reproduce,” I mean that it has to generate something that is or will become something resembling the original. In other words, it has to pass information from one generation to the next. As best as I can tell, my definition as written here includes viruses and rules out fire.
In my experience, what the Star Trek lifesigns-scanner might do is scan for the unique EM spectrum of certain chemical reactions that are almost always present in most lifeforms. This naturally leaves the door open for life forms that their scanners don’t recognize, the inorganic crystal intelligences in “Home Soil” are an excellent example.
First off, Cecil’s take on the subject.
It also includes memes, the written word, DVDs and computer algorithms as being alive, amongst other things… That is obviously problematic since none of those things are alive. Nonetheless all of those things and a great many others are capable of reproducing something resembling the original and they all take in energy. You could also include any useful invention as an example of life by this standard. How many times has the mousetrap managed to generate copies that resemble the original, and how much energy did it take in to do it?
Now I am assuming you will add the qualifier that the energy it needs to take in has to be its “own”, it can’t be human produced energy. The problem with this is that you then immediately exclude most human paraistes and diseases as being alive.
I’ve always liked the reversal of local entropy criterion, but that still doesn’t exclude most human innovations that manage to reproduce themsleves…
How exactly do DVDs or the written word reproduce using this definition:
‘By “reproduce,” I mean that it has to generate something that is or will become something resembling the original’
?
DVDs can recreate what is stored on them but, unless there is some new DVD technology that I don’t know about*, they cannot create new DVDs. Yes, DVDs can be copied but the DVD is NOT generating anything itself. Same thing with memes, algorithms and written works.
Slee
I fail to see the difference between ‘copying the information on a DVD into a new physical medium’ and ‘creating a new DVD’. Can you explain what the difference is? When I burn a DVD and give it to a friend, haven’t I created a new DVD? It seems I must have done since I still posses the original.
I realy don’t see the distinction. When my dog has pups it doesn’t create a duplicate of itself using the same matter. It utilises new matter to create a facsimile. How does this differ from me copying a DVD? In both cases I had one version of something, then I took new matter form another source and onverted that into two verison witht he same approximate information.
I’m really puzzled what you see as being the distinction.
There’s no single property common to all of life, but not to non-life. ‘Family resemblances’ is the basis of demarcation of life from non-life. Phenomena exhibit varying degrees of isomorphism in form and dynamics. Those which fall within a somewhat arbitrary and fuzzy threshold, measured relative to us, qualify as life; those outside, don’t.
Things usually get sticky when I *do * mess around. Okay, bad joke, let’s move along.
Honestly, though, sticky is good. I’m genuinely interested in hearing all points of view on this.
I thought that you folks must have been mind-readers until I clicked on the link and realized that I had read that column some time ago. It must have been rattling around in my brain ever since.
Fire was exactly what I was wondering about. I saw a movie* the other night, and for the first time in my life I looked at fire as a life form rather than a process or a phenomenom (probably because of that column). Fire seems to have form, an appetite, a by-product, and the ability to reproduce itself. Then I started wondering about whether DNA was a requirement, but remembered someone once saying that prions reproduce without DNA. I was a little surprised reading Cecil’s column to find that some folks don’t consider a virus to be alive. I would have guessed that they were, so that would probably disqualify prions as well. Now I am only more confused, but happy to hear what you folks have to say.
“15 Minutes” with DeNiro and Ed Burns. Not a great flick, but the fire scene was well done.
This is what I was wondering; whether there is no hard boundary that defines life, per se, but rather a consensual definition.
Yes, YOU created the new DVD, the DVD did nothing. The specific issue is this phrase:
The DVD has to generate something, it has to DO something to create the next DVD. The DVD does nothing. Someone or something puts the DVD in a DVD player, plays the DVD and a DVD recorder creates the new DVD. The DVD itself isn’t doing anything. It is not acting in anyway. It is being acted upon. Even when you create a new DVD the blank DVD is just being acted upon byt the DVD writer.
When a dog has a puppy you are not doing anything with the creation of the puppy. Nothing else is required to act. The dogs figure it out with out any help and have puppies. DVDs cannot do that, it requires a) someone to take an action and b) something to create the copy of the DVD. A DVD cannot reproduce on its own. Dogs, cats, bactiera and a whole bunch of other things can. DVDs, by themselves, cannot generate anything. Even when you put a DVD in a player the DVD itself really isn’t generating anything, the DVD player is doing all the work.
Slee
Prions are less alive than salt crystals. Salt crystals at least have the ability to act as condensation surfaces to produce salt crystals out of suspended ions, and in so doing produce ordered crystal growth out of a highly entropic suspension. That is more than prions manage. Prions can reproduce only by transforming other equally complex proteins into a different conformation. IOW there is no decrease in entropy or complexity and the level of information produced is les than that found in a salt crystal.
As for whether viruses are alive, that gets tricky. But consider the following. We currently have the ability to read off a virus genome. We can then kill the virus, read the genome out over a telephone to someone who can then write it down on paper, then feed it into a computer that will reassemble the genome in DNA form. Then when we can inject the DNA into a living cell and the virus will continue on as normal.
So the question is, at what point was the virus alive, and at what point was it dead? If it was ever dead did that mean we created life when we injected it into a living cell? If it was never dead then was it alive when it only existed as soundwaves? When it existed as scribbles on a peice of paper? When it existed as pattern of electon flow? And if it was alive in all those forms then why isn’t a computer program or a song alive if it can transfer information that reproduces in those forms?
Thank you, sleestak, for explaining that better than I could. I ran through examples like buildings, etc, before making that distinction in my mind. That’s why a meme or a computer program or any generic piece of information isn’t alive just because it’s information. What makes something alive is that something taking an action or action that generates some new form that preserves some information from the original. Obviously it doesn’t create matter or energy in doing so, but it rearranges matter and energy to do so.
I suppose one could make the argument that fire is passing on information in that it’s giving off photons and jostling air molecules, but I strongly suspect that if one actually distilled some numbers out of measurements of fire, there wouldn’t be any sort of repeating pattern from one second to the next, or from one part of the fire to another.
As far as the virus example, what happened in that scenario is that one individual virus was analyzed and killed. Then certain information was transmitted and someone else made a different instance from that certain information. I would find it very hard to believe that what was created in the second laboratory was exactly the same as the first one. Nevertheless, a very accurate copy was created. There’s a word for this: “cloning.” Notwithstanding that, the virus was capable of reproducing on its own, so it was alive, then it died, and a clone was created.
I still don’t see any logical distinction. The trouble is that ‘do something’ is about as vague as a term can get. "Something’ encompases, well, eveything. A DVD certainly does something insofar as it produces pleasant sensations that lead the host to aid its movement and reproduction. How is that any different to a bacterium that produces unpleasant sensations that lead the host aid its reproduction and movement though sneezing and coughing?
What constitutes an action? Do you need to see self-generated physical movement before it consitutes 'doing something". If this is the case then you are saying that a great many paraistes are not alive since they rely entirley on on thier hosts for their physical movement, just as the DVD does. Is ringworm alive for example, and why is it alive and the DVD not alive?
If my doing ‘something’ to aid reproduction means the unit isn’t alive then most of my parasites are not alive. You really need to use a more specific term than ‘somehting’, since obviously a DVD does something that leads to it being reproduced.
The blank DVD as raw material is indeed just being acted upon by the DVD writer utilising the information extracted form the parent DVD. How is this in any way diffrent from the monomer amino acids and carbohydrates being acted upon by zygote utilising the information extraced from the parent animal?
I really can’t see any but an arbitrary distinction here. We have raw material that is acted upon (blank disc or chemical monomers), we have a peice of hardware specifically engineered to act as a replictaion unit ( zygote or writer), we have an original hardware unit containing information (DVD or animal). The raw material is just acted upon by the writer hardware in both cases, in neither case does the raw material act of its own volition. So what do you see as being the distinction?
What if in the future humanity makes a ‘race’ of sophisticated, spacefaring, insect-like AI robots that act independently of us? They could travel the cosmos, descending upon planets and asteroids looking for fuel and new building material to make newer generations of their basic schematic that are better suited for the different environments they face.
Are they alive?
How is producing a pleasant sensation in the host that makes the host want to assist replication not an action that generates a new form that preserves information from the original? What definition of action are you using here? Are you saying there needs to be physical action?
So a live clone was created, despite the original organism having been dead for 15 years? So an organism was dead for 15 years, then a clone was created, and that clone became alive again? So at what point did the clone become alive? Was the clone alive when it only existed on paper? Was it alive when it only existed as soundwaves? At what point do you define it as being alive, and why did you choose that point?
And how do you define “was capable of reproducing on its own”? A human virus is never capable of reproducing without human intervention. So is the virus alive despite that limitation? And if it is then why was the virus not equally alive when it existed as scribble son a piece of paper? After all the scribbles on the paper were capable of reproducing, but only with human intervention.
Are you saying perhaps that life is defined by whether the intervention of the human is deliberate or unconscious?
I’m saying it’s defined by whether the human intervention is there at all. Consider again the DVD example. The new DVD is created when the computer, via the DVD burner, prints information onto the surface of the laminated disk. Every other part of the process is irrelevant to this discussion. What happens there is that some object other than the raw disk acts on the raw disk to transmit information. If somehow a DVD with information on it could, without human intervention of any kind, produce another DVD with information on it, then it might be alive (assuming that some information was actually passed down).
So now you’re going to say, “That means tapeworms and other parasitic organisms aren’t alive.” Wrong. The tapeworm makes new tapeworms without us taking any action at all, unconscious or otherwise. All we do is provide the raw materials. A streambed could just as easily do the same job had the tapeworm evolved differently. Parasitic (and symbiotic, for that matter) organisms have evolved to use another living organism as their environment, is all.
The virus clone was not alive when it’s genome was on paper, or as sound waves, or anything like that. Because as I said above, a bunch of chicken scratch on a piece of paper cannot do anything without human intervention. Even if the human intervention was unintentional, in this case it would have to do the actual creating of the virus clone, and that’s what makes the information on paper not alive. Once the virus clone is created, however, it can do its own reproducing using the raw material of whatever cells it infects, which means it IS alive.
Well no, that’s not true. If humans didn’t exist the tapeworms would never recieve the hormones they need to compleet there lifecycle. This is why tapeworms are host specific. A stream living flatworm can live in any stream. A mammalian tapeworm can live in only anarrow range of hosts, in some cases only specificlaly in humans. They simply can not produce new tapeworms without the actions of the human body. So by your own standard they are not alive.
I still haven’t seen any objective difference here. You are still using terms like ‘something’ and ‘any action at all’. But the thing is that sneezing or eating contaminated meat or producing hormones or wtring things down are all ‘something’, they are all ‘any action at all’. So you cna not objectively use such criteria to distinguish life from non-life.
Of course if we want to prove how unworkable this deifntion is take a look at paraistic barnacles, These organisms chemically castrate male carbes, then flood their bodies with reporductive hormones that cause them initiate spawning behaviour which releases the parasite’s eggs. Or how about the humble rabbit flea that only produces eggs in response to the pregancy hormone in the blood of a doe. If it doesn’t recieve that hormone it will die of old age and can never reproduce.
These parasites simply can not reproduce without causing the host to help it. Yet by your standards these parasites are not alive because they can’t reproduce without another species taking action to enable it.
But that is a total non sequitur. Why is it alive if it can reproduce using the raw material in the cells and by inducing the host to sneeze, but not alive if it can use the raw materials in the laboriataory and by inducing the host to write down more copies of itself?
I think you really need to define what objective difference you see here. Terms like ‘something’ and ‘anyhting at all’ clearly are not providing any objective difference. So what precisely is the objective difference that you see? Can you explain that, rather tha using terms like ‘somehting’ or ‘anything’ that clearly don’t explain anything becuase they are all-encompassing.
Do the hormones the tapeworms recieve actually create the baby tapeworms? If not, the human body doesn’t make the baby tapeworms, the adult tapeworm does. Host specificity is irrelevant. The critical question is, what does the actual reproduction?
Those parasitic barnacles? If all they do is use the crab as a house and then cause the crab to let them go, the crab doesn’t make new barnacles, the barnacles make new barnacles. That humble rabbit flea needs a trigger to reproduce, but it still makes its own eggs. Hell, every mammal that goes into seasonal estrus needs a trigger to reproduce. It’s not the enabling, it’s the actual making of the new organism.
How does a virus genome written on a piece of paper actually induce a person to make a virus clone?
The objective difference is, does the organism in question require some external process to actually produce a duplicate? A canine does not, it’s alive. A DVD does, it is not alive. When a dog reproduces, the materials, the matter itself, come from outside of the dog, but the dog assembles them into a canine embryo, which matures and then comes out of the dog. When a DVD is copied, the materials, the matter itself, come from outside of the DVD, but the DVD does not do the assembling into a new DVD.
First you need to define what you even mean by ‘actual reproduction’. You still haven’t provided anything objective that we can use despite being asked several times.
Let me put it like this, if I say that the human does the actual reproduction and the tapeworm merely provides the information and abasic template then by what objective standard am I incorrect?
By providing them with research results, thus money, prestige etc. Of course music provides a much more direct inducement by producing pleasant sensations that lead to it being reproduced
Wrong. By this objective standard any organism that requires some external process to actually produce a duplicate is not alive. Once again your definition relies on the all encompassing ‘Some external process’, which is no improvement over ‘anything at all’ or ‘something’. All organisms require ‘some external process’ to produce a duplicate. Even a dog can’t reproduce without eating, and the death of a prey animal is indisputably ‘some external process’.
Many fish are not living things by this standard because the eggs and sperm are shed into the water and fertilisation occurs there. The materials, the matter itself that makes up a new fish come form outside the fish, the fish does not do the assembling into a new fish or even a new zygote. This is clearly not a workable standard to attempt to apply to life and fish are clearly living things regardless of whether new fish are assembled from matter outside of the parent fish.
Quite simply put the idea that living things have to assemble their offspring internally doesn’t stand up to even cursory examination since the vast majority of creatures do not assemble offspring internally.
A dog eating isn’t an external process of reproduction, it’s the dog taking in the energy and materials needed for the internal process of reproduction.
Define “external process of reproduction” to mean “the process of producing a copy of an organism without any matter or energy moving directly from the original to the copy.” Then my previous statement works.
Then obviously humans are not alive because humans require all kinds of other species (like trees) to reproduce. To reproduce humans must be alive. To live humans require oxygen. The oxygen comes from plants. The plants require the sun, earth and a whole lot of other things to produce the oxygen. Therefore humans are not alive because humans cannot live without the hosts (earths)help. Which is absolute nonsense.
It seems to me that you are confusing what a life form requires to live with whether or not that it is actually alive. The fact that a tapeworm requires a human hormone to live is irrelevant to whether or not it is alive. Humans require oxygen. Does that mean that humans are not alive?
You speak of us being vague by using the term ‘something’ then pop out with this:
What actions, exactly, do DVDs undertake to reproduce?
Slee