Anyway, viruses seem so clearly to be living things that any definition of life which would exclude viruses is a bad definition of life. Any definition of life needs to be broad enough to include both eukaryotes and viruses.
@deathpigeon that's a spicy take. are robots alive? are computer scripts alive? viruses are essentially a self-replicating algorithm and not at all self-regulating, so they cannot be alive. viruses are literally just containers for RNA to modify other cells. what significant factor leads you to claim that a virus is "so clearly" alive?
1) algorithms evolve
2) computer code can reproduce
3) scripts act "independently"
4) a program can generally act however it's programmed
That's not enough to define life. And viruses don't even act or reproduce independently -- they require a host to propagate, and are otherwise just floating around waiting to run into a host.
- are not made of cells
- don't grow
- don't metabolize energy
- don't exhibit any homeostatic behavior
@trwnh Life very obviously didn't start out made in cells. It had to have developed cells at some point. Same with metabolized energy and homeostatic behavior. Growth, maybe, but even that seems sketchy. Those are problems with your definition of life, not with viruses.
And scripts hardly act independently. They require some outside source to actively start them on their tasks, for example.
@deathpigeon OK, let me try to break it down:
- Implanting genetic material is not the same as creating your own.
- "independently" implies acting alone, which viruses are categorically incapable of doing.
- Replication and reproduction are technically different processes.
- Genetic material alone is not enough to be alive.
@deathpigeon In short, viruses cannot mechanically move in a self-directed manner and are subject to movement solely based upon environmental interactions. Their replication process is the only similarity to life, and only because they hijack a living cell to do it.
@trwnh Mechanical movement in a self-directed manner seems unnecessary, to me, for something to be life. If a bacteria evolved such that it lost it's ability to mechanically move in a self-directed manner, you wouldn't stop calling it life, would you?
Independently seems to mean, to me, in this context, that they direct it rather than that they do it alone, ie parasites infecting a host are acting independently.
@trwnh Finally, at no point did I suggest genetic material is enough to be alive. In fact, I don't even really think it's necessary to be alive. If we discovered otherwise life-like things on another planet which lacked genetic material, I would be prepared to call it life. Similarly, if robotics became advanced enough that it could act life-like in all other ways, such as a Von Neumann probe, I'd also be prepared to call it life.
>If a bacteria evolved such that it lost it's ability to mechanically move in a self-directed manner, you wouldn't stop calling it life, would you?
What would that entail, though? Losing the ability to move would be a disadvantageous mutation because bacteria depend on movement to get enough nutrients. Which, coincidentally, is something viruses don't need to worry about, because they don't need it.
>they direct it rather than that they do it alone
A virus isn't directed at all.
>If we discovered otherwise life-like things on another planet which lacked genetic material, I would be prepared to call it life.
This is indeed the crux of your argument, and simultaneously the thing I find the most problematic. "Life-like" =/= "alive". And the only characteristic of life that you keep referring to is the ability to multiply. You just don't distinguish between replication and reproduction.
@trwnh I mean, the details of the hypothetical are irrelevant because the purpose is to suss out the definition of life. But, like, surely you're aware of bacteria which get their nutrients through photosynthesis, right?
How is the virus not directed at all?
And it's a good thing I never said life-like is the same as alive. Also, you're assuming those characteristics constitute a good definition of life while I'm not.
Finally, yes, if a virus couldn't replicate, it wouldn't be alive.
@deathpigeon OK, but a bacterium depending on photosynthesis would die if it was placed outside of the sun and unable to gather solar energy.
And still, the bacterium can direct its organelles to perform a task. A virus cannot direct anything, and it has nothing to direct.
I'm just trying to find out what your definition of "life" is such that it seems predicated heavily (if not wholly) on replication (which is still not the same as reproduction).
re: a definition, this is the closest I could find: https://left.community/@deathpigeon/100196580976509720 -- and in the immediate reply I challenged every single one of those characteristics. Virus evolution is limited only to transcription errors. Virus do not reproduce, they replicate. They are not independent in any way, and cannot do anything. They do not "act like life" except when they explicitly hijack life.
Since the 2nd point of contention seems to be the definition of "direction", please offer one.
@trwnh Transcription errors being involved in evolution doesn't make it not evolution? What?
I find the distinction between reproduction and replication to be philosophically uninteresting. For the purpose of determining if something is living or not, distinguishing between them doesn't help us.
Self-directed roughly means originating from the self.
>For the purpose of determining if something is living or not, distinguishing between them doesn't help us.
Well, that just seems illogical. Why would it be unimportant? It seems like a crucial distinction to make. One generates exact copies, bar some mistakes. The other generates a different object. Virus cannot produce offspring. Even in asexual reproduction, an organism reproduces **without the involvement of another organism**.
@trwnh Because "exact copies, bar some mistakes" and "a different object" isn't a difference? And the necessity of doing it without another thing doesn't seem to be all that relevant. Do animals which have evolved to only be able to reproduce by implanting eggs in another species of animal not count? It's more macroscopic than viruses, but it still is only able to be done with the involvement of another organism.
@deathpigeon No, because that would be *sexual* reproduction. Viruses cannot sexually reproduce any more than they can asexually reproduce. Again, they *only* replicate. Yes, this is a distinction that matters, because when living organisms reproduce, they produce a child that inherits code from the parent. The child is more than just code.
@trwnh That seems like an entirely ad hoc distinction. Why is it that characteristics which would discount an asexual reproducer from being a reproducer wouldn't also discount a sexual reproducer? I mean, if we want a rigorous definition of life, surely we need it to be the same for both asexually reproducing and sexually reproducing life, which your definition is failing at.
@deathpigeon Well, the definition of life includes "reproduction", but that says absolutely nothing about the different types of reproduction. So the definition is still the same -- what you mean to be addressing is the definition of *reproduction*, not the definition of life.
@deathpigeon Let me clarify again:
- Reproduction is a necessary (but not sufficient) characteristic of life.
- Reproduction is the act of producing offspring, not a replica.
- Asexual reproduction is done without another organism.
- Sexual reproduction is done by fusing gametes.
- Replication is done by transcribing and translating DNA, and produces replicas instead of offspring.
@deathpigeon Well, there's the circular definition of "offspring are living organisms", but this really just demonstrates why environmental responses are another necessary factor of life -- a genetic clone will NOT end up identical to the parent. By contrast, there is no functional difference between any two viruses of the same type because they are replicas, not offspring. The code within the virus does NOT respond to environment, nor does it dictate growth (because there is no growth).
@trwnh Ok, so, if we assume the Regressive Hypothesis of virus evolution is correct, which, to be clear, I don't think it is, but I feel it demonstrates a flaw in your reasoning, there must've been at one point a cell more like other living things than a virus which produced an offspring which was more like a virus than other living things, but, if we go by that, then that cell couldn't've been alive, nor the cell that produced it, nor the cell which produced it, etc.
That tweet was a hot take, but wait until you hear this: I think Von Neumann probes would constitute as alive.
*Takes a look at the discourse.* Ok, here's a question: Are Von Neumann probes socialist?