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.
> Most concepts in biology break down on the borderline cases
Most concepts break down on borderline cases, within and without biology. Those motivated will abuse this to argue that those concepts don't meaningfully exist at all.
Because in most cases the categories are invented by us, to make sense of the world. But the penomena themselves are often continuous. Or actually not just us but most life with some kind of sensory system - even paramecium differentiates between food and non-food.
Take our color perception as an obvious example: We clearly see different types of color, despite us being unsure at the thresholds in between, and the actual electromagnetic radiation of visible light being a continuous wavelength range.
That is just a fundamental limit of our reasoning. We mentally make models of the world to make sense of it. These models have to be of less complexity than reality, ergo they have to cluster perceptions, ergo we have to categorize.
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.
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.
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.
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.
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 '
> 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.
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.
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.
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.
Oh wow, that looks a lot more complex than I expected for something that's supposed to be extremely "stripped down" from a genomic POV.
I mean, I know the article mentions it "has its own ribosomes, cellular structures that synthesize proteins, and it can replicate itself without the help of a host" but that doesn't always translate to complex structures plainly visible underneath a microscope.
My biology is a bit rusty but I really have to wonder — are plants and animal cells even “alive”?
Take away the mitochondria and bacteria… can cells live on their own?
If no, then are we that all that different than this microbe?
Might even be sheer arrogance to think that we are the “host” (much like cats/dogs domesticating humans). Maybe we only exist to serve the mitochondria (:->
>We can live without bateria if we add with some food supplements.
Citation needed. I would strongly doubt that this is true, because microbes also play a very important role in eg. immune defense. Remove all the mutualitic microbes from a human (eg skin, digestive tract) and the parasitic and pathogenic bacteria will take their place immediately.
We're talking removing all bacteria. And we know it's possible - even if it can't happen in nature.
There are sterile mice made for scientific uses - 100% mouse, completely microorganism free or your money back. They have health issues, but they can survive and reproduce in the right conditions.
Of course, those "right conditions" include sterile housings and sterilized food, because they'll get contaminated otherwise.
My bio is rusty but I remember that archaeon are into extreme situations. Is it so weird to find an example of one essentially “offloading” some functionality to its host? Especially in a diluted environment like the oceans
I've always felt like the biological definition of life isn't useful or meaningful when it comes to borderline replicators like viruses.
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.
> Most concepts in biology break down on the borderline cases
Most concepts break down on borderline cases, within and without biology. Those motivated will abuse this to argue that those concepts don't meaningfully exist at all.
Because in most cases the categories are invented by us, to make sense of the world. But the penomena themselves are often continuous. Or actually not just us but most life with some kind of sensory system - even paramecium differentiates between food and non-food.
Take our color perception as an obvious example: We clearly see different types of color, despite us being unsure at the thresholds in between, and the actual electromagnetic radiation of visible light being a continuous wavelength range.
That is just a fundamental limit of our reasoning. We mentally make models of the world to make sense of it. These models have to be of less complexity than reality, ergo they have to cluster perceptions, ergo we have to categorize.
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.
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.
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.
Analyze a word you think has a crystal clear definition.
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.
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 '
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.
> 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.
> 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?
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.
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.
I mean, humans are just a definition away from being a single globe-spanning morphing organism.
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-o...
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.
Too bad, I was hoping for an electron microscope photo or something.
Here you go: https://indiandefencereview.com/scientists-organism-living-n...
Oh wow, that looks a lot more complex than I expected for something that's supposed to be extremely "stripped down" from a genomic POV.
I mean, I know the article mentions it "has its own ribosomes, cellular structures that synthesize proteins, and it can replicate itself without the help of a host" but that doesn't always translate to complex structures plainly visible underneath a microscope.
My biology is a bit rusty but I really have to wonder — are plants and animal cells even “alive”?
Take away the mitochondria and bacteria… can cells live on their own?
If no, then are we that all that different than this microbe?
Might even be sheer arrogance to think that we are the “host” (much like cats/dogs domesticating humans). Maybe we only exist to serve the mitochondria (:->
I think I first came across this on HN: A Symbiotic View of Life: We Have Never Been Individuals [0]
[0]https://www.journals.uchicago.edu/doi/10.1086/668166
> Take away the mitochondria and bacteria… can cells live on their own?
We can live without bateria if we add with some food supplements.
mitochondria isn't considered alive, as a separate organism, AFAIK. It doesn't even have a species name. It's just a component of the host cell.
As I understand it, these new microorganisms are parasites. They're not essential for the functioning of the host cell like mitochondria are.
Mitochondria were(are?) bacteria, so technically we can't live without bacteria really.
>We can live without bateria if we add with some food supplements.
Citation needed. I would strongly doubt that this is true, because microbes also play a very important role in eg. immune defense. Remove all the mutualitic microbes from a human (eg skin, digestive tract) and the parasitic and pathogenic bacteria will take their place immediately.
We're talking removing all bacteria. And we know it's possible - even if it can't happen in nature.
There are sterile mice made for scientific uses - 100% mouse, completely microorganism free or your money back. They have health issues, but they can survive and reproduce in the right conditions.
Of course, those "right conditions" include sterile housings and sterilized food, because they'll get contaminated otherwise.
When you say "take away the mitochondria," do you mean a prokaryote?
Mitochondria can't live without their surrounding cells. Plants are also interdependent with fungi.
Multicellular life is difficult without mitochondria. Personally I think that is the great filter.
"it takes a planet to make life"
My bio is rusty but I remember that archaeon are into extreme situations. Is it so weird to find an example of one essentially “offloading” some functionality to its host? Especially in a diluted environment like the oceans
More evidence for the life-exists-on-a-spectrum idea.