5 ms·

I've always felt like the biological definition of life isn't useful or meaningful when it comes to borderline replicators like viruses.

Teknomadix 1y ago
Similarly, the standard definitions of intelligence break down when we look at borderline cases like simple algorithms, collective insect behavior, or AI systems. Viruses particularly exemplify “intelligence” is better understood as a spectrum of information-processing and adaptive behaviors rather than a strict threshold. The issue seems to me that neither concept is wrong, but that we humans keep trying to impose absolute definitions on phenomena that exist along continua, blurring into one another in ways that resist our neat little categorizations. I would argue viruses exemplify some of the highest evolved intelligence in our world.
adrian_b 1y ago
In my opinion, a virus in the environment is quasi-dead, but once it enters a cell and it hijacks its components, it becomes alive. This does not differ that much from bacterial or fungal spores, or even from plant seeds, which can also be almost "dead", i.e. without detectable metabolism or internal changes, even over many thousands of years, until they reach a favorable environment that triggers their revival. The difference between a virus and a bacterial spore is that the viral particle contains only a subset of the parts of a living organism, so it could never be brought back to life in an environment where nothing is already alive. However, once the virus takes control over many parts of a cell, which provide the functions that it is missing, like the machinery for protein synthesis, the ensemble formed by the parts brought by the viral particle and the parts formerly belonging to the invaded cell, can be considered as alive and distinct from what the invaded cell was previously. In any case, the evolution of the viruses and the evolution of the cellular forms of life are entangled, with a lot of genetic material exchanged between them, so considering the viruses as non-living is definitely counter-productive, because neither the viruses nor the cellular forms of life can be understood separately.
- djmips 1y ago
  That's a pretty cool framework for the alive or dead debate. I've always been firmly on the alive side but now I can do a better job of presenting the argument concretely instead of just ' nuh-uh '
- close04 1y ago
  > so it could never be brought back to life in an environment where nothing is already alive I always thought of a virus as purely a "modifier", not having the characteristics of "life" independently. If this was a game, the virus might be a runestone or skin for your character. Anything that doesn't need external "life" to come alive, I would consider as "life" in various states. Maybe it's in hibernation, or stasis, or dormant but the life is there. Maybe to keep the silly game analogy, this might be the extra character on your roster.
  - klez 1y ago
    > Anything that doesn't need external "life" to come alive, I would consider as "life" in various states Doesn't almost any biological entity need external life to come alive via, e.g. reproduction or mitosis or what have you?
    - close04 1y ago
      Yes but you are talking about the threshold of existence, and the cell is alive as soon as it starts existing. For a virus you also have the threshold of "application", when the viral code is applied to something alive. Before that the virus exists but is not alive itself. After the application it's modifying other life which maybe technically can be considered alive. This is why I said "to come alive" instead of "to be created". The virus is something that just exists but only becomes alive when mixed with something that's already alive.
- eru 1y ago
  The virus behaves a bit like the seed of certain plants (like many orchids) that need obligatory symbionts. The seed by itself is not viable.
go_photon_go 1y ago
Useful, but not exact. To go more general in biology. It's kind of like classical pre-cladistics taxonomy. It's helpful to have a definition of reptiles that excludes birds, sometimes, even if birds are evolutionarily reptiles, sometimes you might only want to talk about the cold-blooded species today.
M95D 1y ago
I prefer the Erwin Schrödinger's definition more. PS: There's more recent work done on this: https://www.quantamagazine.org/a-new-thermodynamics-theory-of-the-origin-of-life-20140122/ https://www.quantamagazine.org/a-new-thermodynamics-theory-o...
griffzhowl 1y ago
Most concepts in biology break down on the borderline cases, because the phenomena are so complicated with all the little variations, the concepts have an inherent fuzziness. Instead of the concepts being like a box where something is definitely in the box or not in the box like in mathematics or maybe physics, the concepts are more like a clustering of characteristics in a high-dimensional space or landscape of variation, where things are classified according to their similarity to a central paradigm case. (This seems to be how our minds model at least some concepts as well, as evidenced by our being faster at categorising cases that are closer to some paradigm case) One notorious example is the concepts of male and female: yes, there are borderland examples of individuals who can't be classified as either, but almost everyone clusters sufficiently closely to the distinct paradigmatic cases that the concept has an obvious utility. But the same thing happens everywhere in biological classification: whether something is a mammal or not becomes fuzzy as we go back in evolutionary time, and whether something is alive or not is similar.
- klez 1y ago
  Sure, but considering how central and defining the concept of "life" is to biology (the study of life and living organisms) you'd think we wouldn't have a fuzzy definition for that specific concept. I can see why it's tricky, though.
  - eru 1y ago
    We really only have one example of life (or at least all our examples are interconnected), so I don't expect great definitions. Just like geology doesn't have a great definition for their subject of study (the earth). They have a definition that works really well, but because they only have one example, the definition ain't stress tested. Slightly less silly: it took the discovery of lots more bodies inside and outside the solar system (dwarf planets here, exoplanets elsewhere) for astronomers to really nail down the definition of planet.
  - griffzhowl 1y ago
    I think that depends on your prior expectations about how biological concepts should be structured. I was trying to make the case that we should expect that they're fuzzy when we're dealing with very complex phenomena that exhibit a lot of variation. The fact that these kinds of phenomena happen to exhibit clustering is what makes (fuzzy) classification possible, but we also find that many phenomena or organisms are in borderland areas between clusters, so the classification doesn't work as well with them.
amelius 1y ago
I mean, humans are just a definition away from being a single globe-spanning morphing organism.
jacquesm 1y ago
This is just another way to say that the map is not the territory. Anything that tries to describe reality in simpler terms than actual reality is likely just going to end up being a leaky abstraction rather than a hard law. And nature is very fuzzy along the boundaries of whatever concepts you are going to come up with.
schiffern 1y ago
If you dropped me off in vacuo (eg in deep space), I wouldn't meet the definition of "alive" either. But the fact that my life require a specific environment doesn't phase us or challenge our definition of life at all. Not only do I need certain physical conditions (temperature, pressure, molecular gas composition, etc), but I also need to eat, so actually me being "alive" is dependent on specific biological conditions too. My Minimum Viable Environment actually includes other organisms, yet this doesn't challenge the fact that I'm defined as alive. Certain parasites can only live or reproduce within another organism. This is even more extreme, but it still doesn't challenge our definition of them as being "alive." This new organism requires a specific "environment," and that "environment" happens to be inside another organism. So what? We're totally un-phased by this requirement when it occurs in other examples. Perhaps it's better to think of this not as a spectrum between alive and non-living, but as a hierarchy of how constrained (vs unconstrained) is the "environment" required to support life processes.
- schiffern 1y ago
  TL;DR if aliens exist they probably define us as "partly alive" because we can't reproduce outside a planet. :D

Teknomadix 1y ago

Similarly, the standard definitions of intelligence break down when we look at borderline cases like simple algorithms, collective insect behavior, or AI systems. Viruses particularly exemplify “intelligence” is better understood as a spectrum of information-processing and adaptive behaviors rather than a strict threshold. The issue seems to me that neither concept is wrong, but that we humans keep trying to impose absolute definitions on phenomena that exist along continua, blurring into one another in ways that resist our neat little categorizations. I would argue viruses exemplify some of the highest evolved intelligence in our world.

adrian_b 1y ago

In my opinion, a virus in the environment is quasi-dead, but once it enters a cell and it hijacks its components, it becomes alive. This does not differ that much from bacterial or fungal spores, or even from plant seeds, which can also be almost "dead", i.e. without detectable metabolism or internal changes, even over many thousands of years, until they reach a favorable environment that triggers their revival. The difference between a virus and a bacterial spore is that the viral particle contains only a subset of the parts of a living organism, so it could never be brought back to life in an environment where nothing is already alive. However, once the virus takes control over many parts of a cell, which provide the functions that it is missing, like the machinery for protein synthesis, the ensemble formed by the parts brought by the viral particle and the parts formerly belonging to the invaded cell, can be considered as alive and distinct from what the invaded cell was previously. In any case, the evolution of the viruses and the evolution of the cellular forms of life are entangled, with a lot of genetic material exchanged between them, so considering the viruses as non-living is definitely counter-productive, because neither the viruses nor the cellular forms of life can be understood separately.

djmips 1y ago
That's a pretty cool framework for the alive or dead debate. I've always been firmly on the alive side but now I can do a better job of presenting the argument concretely instead of just ' nuh-uh '
close04 1y ago
> so it could never be brought back to life in an environment where nothing is already alive I always thought of a virus as purely a "modifier", not having the characteristics of "life" independently. If this was a game, the virus might be a runestone or skin for your character. Anything that doesn't need external "life" to come alive, I would consider as "life" in various states. Maybe it's in hibernation, or stasis, or dormant but the life is there. Maybe to keep the silly game analogy, this might be the extra character on your roster.
- klez 1y ago
  > Anything that doesn't need external "life" to come alive, I would consider as "life" in various states Doesn't almost any biological entity need external life to come alive via, e.g. reproduction or mitosis or what have you?
  - close04 1y ago
    Yes but you are talking about the threshold of existence, and the cell is alive as soon as it starts existing. For a virus you also have the threshold of "application", when the viral code is applied to something alive. Before that the virus exists but is not alive itself. After the application it's modifying other life which maybe technically can be considered alive. This is why I said "to come alive" instead of "to be created". The virus is something that just exists but only becomes alive when mixed with something that's already alive.
eru 1y ago
The virus behaves a bit like the seed of certain plants (like many orchids) that need obligatory symbionts. The seed by itself is not viable.

go_photon_go 1y ago

Useful, but not exact. To go more general in biology. It's kind of like classical pre-cladistics taxonomy. It's helpful to have a definition of reptiles that excludes birds, sometimes, even if birds are evolutionarily reptiles, sometimes you might only want to talk about the cold-blooded species today.

M95D 1y ago

I prefer the Erwin Schrödinger's definition more. PS: There's more recent work done on this: https://www.quantamagazine.org/a-new-thermodynamics-theory-of-the-origin-of-life-20140122/ https://www.quantamagazine.org/a-new-thermodynamics-theory-o...

griffzhowl 1y ago

Most concepts in biology break down on the borderline cases, because the phenomena are so complicated with all the little variations, the concepts have an inherent fuzziness. Instead of the concepts being like a box where something is definitely in the box or not in the box like in mathematics or maybe physics, the concepts are more like a clustering of characteristics in a high-dimensional space or landscape of variation, where things are classified according to their similarity to a central paradigm case. (This seems to be how our minds model at least some concepts as well, as evidenced by our being faster at categorising cases that are closer to some paradigm case) One notorious example is the concepts of male and female: yes, there are borderland examples of individuals who can't be classified as either, but almost everyone clusters sufficiently closely to the distinct paradigmatic cases that the concept has an obvious utility. But the same thing happens everywhere in biological classification: whether something is a mammal or not becomes fuzzy as we go back in evolutionary time, and whether something is alive or not is similar.

klez 1y ago
Sure, but considering how central and defining the concept of "life" is to biology (the study of life and living organisms) you'd think we wouldn't have a fuzzy definition for that specific concept. I can see why it's tricky, though.
- eru 1y ago
  We really only have one example of life (or at least all our examples are interconnected), so I don't expect great definitions. Just like geology doesn't have a great definition for their subject of study (the earth). They have a definition that works really well, but because they only have one example, the definition ain't stress tested. Slightly less silly: it took the discovery of lots more bodies inside and outside the solar system (dwarf planets here, exoplanets elsewhere) for astronomers to really nail down the definition of planet.
- griffzhowl 1y ago
  I think that depends on your prior expectations about how biological concepts should be structured. I was trying to make the case that we should expect that they're fuzzy when we're dealing with very complex phenomena that exhibit a lot of variation. The fact that these kinds of phenomena happen to exhibit clustering is what makes (fuzzy) classification possible, but we also find that many phenomena or organisms are in borderland areas between clusters, so the classification doesn't work as well with them.

amelius 1y ago

I mean, humans are just a definition away from being a single globe-spanning morphing organism.

jacquesm 1y ago

This is just another way to say that the map is not the territory. Anything that tries to describe reality in simpler terms than actual reality is likely just going to end up being a leaky abstraction rather than a hard law. And nature is very fuzzy along the boundaries of whatever concepts you are going to come up with.

schiffern 1y ago

If you dropped me off in vacuo (eg in deep space), I wouldn't meet the definition of "alive" either. But the fact that my life require a specific environment doesn't phase us or challenge our definition of life at all. Not only do I need certain physical conditions (temperature, pressure, molecular gas composition, etc), but I also need to eat, so actually me being "alive" is dependent on specific biological conditions too. My Minimum Viable Environment actually includes other organisms, yet this doesn't challenge the fact that I'm defined as alive. Certain parasites can only live or reproduce within another organism. This is even more extreme, but it still doesn't challenge our definition of them as being "alive." This new organism requires a specific "environment," and that "environment" happens to be inside another organism. So what? We're totally un-phased by this requirement when it occurs in other examples. Perhaps it's better to think of this not as a spectrum between alive and non-living, but as a hierarchy of how constrained (vs unconstrained) is the "environment" required to support life processes.

schiffern 1y ago
TL;DR if aliens exist they probably define us as "partly alive" because we can't reproduce outside a planet. :D