HN Distilled

Essential insights from Hacker News discussions

Tiny microbe challenges the definition of cellular life

Original Article

Hacker News Discussion

This Hacker News discussion explores the blurry lines between living and non-living entities, particularly focusing on viruses, and extends this to broader biological concepts and the nature of intelligence. A core theme is the inadequacy of rigid, absolute definitions for phenomena that exist on continua.

Life as a Spectrum, Not a Binary

A dominant sentiment is that concepts like "life" and even "intelligence" are better understood as existing on a spectrum rather than as strict, binary classifications. This is exemplified by discussions around viruses and other borderline cases.

  • "Teknomadix: Similarly, the standard definitions of intelligence break down when we look at borderline cases like simple algorithms, collective insect behavior, or AI systems."
  • "Teknomadix: Viruses particularly exemplify 'intelligence' is better understood as a spectrum of information-processing and adaptive behaviors rather than a strict threshold."
  • "Teknomadix: The issue seems to me that neither concept is wrong, but that 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."
  • "faisa1: More evidence for the life-exists-on-a-spectrum idea."
  • "go_photon_go: 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."

Viruses as Borderline or Integrated Life

The discussion frequently revisits viruses as prime examples of entities that challenge traditional definitions of life. Some argue they are "quasi-dead" until they hijack a host, while others see them as integral to the evolutionary tapestry of life.

  • "wagwang: I've always felt like the biological definition of life isn't useful or meaningful when it comes to borderline replicators like viruses."
  • "adrian_b: 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."
  • "adrian_b: 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."
  • "adrian_b: 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."
  • "close04: 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."
  • "close04: 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: 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."
  • "admin_account: 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?"

The Interdependence of Life and the Concept of the "Individual"

Several comments highlight the deep interdependence of biological entities, questioning the notion of a singular, independent "individual" and suggesting that life is inherently a collective or symbiotic phenomenon.

  • "BobbyTables2: 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?"
  • "BobbyTables2: 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 (:->)"
  • "chasil: When you say 'take away the mitochondria,' do you mean a prokaryote?"
  • "hydrogen7800: I think I first came across this on HN: A Symbiotic View of Life: We Have Never Been Individuals [0]"
  • "DemocracyFTW2: 'it takes a planet to make life'"
  • "pabs3: Mitochondria can't live without their surrounding cells. Plants are also interdependent with fungi."
  • "Algernon: '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."

The Limitations of Human Categorization

A recurring theme is the human tendency to impose rigid, often insufficient categories onto complex, naturally occurring phenomena. The fuzziness of biological concepts is seen as a reflection of these limitations rather than a flaw in the phenomena themselves.

  • "griffzhowl: 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."
  • "griffzhowl: 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)."
  • "griffzhowl: 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."

Alternative and Evolving Definitions of Life

The discussion touches upon the ongoing scientific efforts to define life, referencing specific theoretical frameworks.