10 ms·

Considering that the first proto-computers were not programmable, I can't help but be skeptical that the first life needed genetic material. Certainly there we

• angst_ridden 6y ago
  I think you've got a minority opinion calling crystals "alive," although it does jibe with one definition of life that I heard: "any self-sustaining system that reduces internal entropy."
  • DanBC 6y ago
    Dawkins doesn't call crystal structures alive, but he does mention them as a potential hypothetical source for life. http://www.bbc.co.uk/earth/story/20160823-the-idea-that-life-began-as-clay-crystals-is-50-years-old http://www.bbc.co.uk/earth/story/20160823-the-idea-that-life... > Cairns-Smith found a more eager audience in science journalists and the popular press. Other scientists showed interest, too: the evolutionary biologist and writer Richard Dawkins discussed the crystals-as-genes hypothesis in his 1986 book The Blind Watchmaker. [...] > His aim was to find a system much simpler than modern life, but which had some of the crucial properties of a living system. He found an answer in an unlikely place: clays.
  • kevmo 6y ago
    That's one place where my "What is Life?" college class landed.
  • adrian_b 6y ago
    While obviously crystals are not alive, they satisfy more careless definitions of life that were sometimes encountered, i.e., when put in a "nutritive" solution, they are able to grow and reproduce themselves.
    • beowulfey 6y ago
      I think even under that definition they don't truly reproduce and still aren't really life -- they don't create the same material they arise from for example (so not allowing for additional crystals to form). A non-renewing source of the material has a maximum amount of crystal that can grow, I would imagine. This is different than something like a virus, which carries the instructs to replicate itself and the ability to travel to new hosts to create more of itself (and still isn't really considered alive).
      • Ericson2314 6y ago
        > A non-renewing source of the material has a maximum amount of crystal that can grow So any biosphere that fails to escape its looming red giant was never alive? I'm not a "all abstractions leak" type of person, so I will choose my definitions very carefully, with funny choices about clays, crystals, virus, etc. as an acceptable causality.
    • dekhn 6y ago
      This is just wrong (as you say, careless). The criteria is "metabolism", not growth and reproduction. Similarly, viruses are not alive although they can reproduce. Interestingly, there are some highly parasitic organisms with limited ability to metabolize, that is, they have lost their genes and instead depend on their host organism (but I think all those examples still have some level of metabolic capability).
      • Ericson2314 6y ago
        I don't really know what "metabolism" means, abstractly. I am deader than a virus without chloroplasts existing elsewhere. Viruses need a host for the productive bit, I had food for the non-reproductive bit. Viruses don't break down fast enough compared to their abundance to cause extinction, so why fault them for optimizing? People commonly theorize that virus came from rump parasitic cells. I wouldn't be surprised if at some point a huge virus with a membrane accidentally picked up enough stuff to become a cell again. To go back to chloroplasts again, it would be like how brown algae is an ex-heterotroph.
  • Razengan 6y ago
    > "any self-sustaining system that reduces internal entropy." Planet Earth would/should definitely count as alive, especially if it "reproduces" via us terraforming other planets to become like Earth.
    • angst_ridden 6y ago
      There are plenty of conceptualizations of planet-as-organism, e.g., Gaia Hypothesis.
    • whimsicalism 6y ago
      Ultimately, this is a semantic debate trying to apply human linguistic constructions to physical processes.
      • tw25508394 6y ago
        Amen! This is about as useful as debating whether Pluto is a planet.
      • dilawar 6y ago
        Good plot for Rick and Morty. Wait, they already did it.
    • SuoDuanDao 6y ago
      It seems nonsensical in any case to claim something that contains life among its constituent parts is not itself alive. Plenty of organisms have 'dead' tissue as part of their gestalt and no one thinks of them as 'mostly' alive.
      • cossatot 6y ago
        Life isn't a constituent part of the Earth. It's a coating.
        • Razengan 6y ago
          That statement is such a gross oversimplification of a tiny fraction of the whole picture. Life permeates deep into Earth and even influences its geology: https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole#Research https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole#Resear... https://en.wikipedia.org/wiki/Petroleum https://en.wikipedia.org/wiki/Petroleum
  • api 6y ago
    My favorite version of this classifies life as an exotic phase of matter in the sense of other exotic phases like Bose-Einstein condensates, etc. Life is a phase of matter in which the dynamics of information and Turing-complete computation overcome the ordinary dynamics of matter and energy. I am not aware of who originated this idea, but I heard it from Christoph Adami (a researcher in evolutionary information theory). I also recall someone at a conference proposing the term "Turium," for "Turing-complete phase of matter." Earth just happens to have an environment that contains a large abundance of this phase of matter, much like how stars are full of plasma etc.
    • kubanczyk 6y ago
      How is this model useful? It certainly moves away from our domain knowledge and paints a new picture that is considerably more fuzzy than the old one. What do you gain by considering life in such way? Side note: computation seems like a wrong term, because it's not about counting/calculating/determining any abstract value, is it? A Turing-complete mechanism maybe?
      • api 6y ago
        I find the idea of it as a phase of matter very conceptually elegant in that it neatly classifies life as a unique but still physical phenomenon. Nevertheless I agree with you that the details of the definition are hard to pin down. Of course I have yet to see an attempted definition of life that isn’t a little squirrely or that isn’t just a list of criteria taken from the one example we have.
  • snowwrestler 6y ago
    Crystals don’t reduce their internal entropy. They grow only on the interface with the media, and the portions of the crystal that become internal during this process do not change after crystallization if kept at constant temp and pressure. In contrast, if you put a plant and its media (soil, air, water) into constant temp and pressure, the plant will continue to grow and change until it exhausts the media. (assuming the temp and pressure are conducive to life) Ultimately plants become their own media by decomposing into soil.
    • BlueTemplar 6y ago
      If an external disturbance scatters the atoms inside the crystal, they will snap back to the lattice again. In a way similar (up to a point) to "normal" living organism's homeostasis.
• proc0 6y ago
  How would you define genetic material? I think some kind of movement and a metabolism can already be called alive. It's not so much about the material but rather the interaction between the materials that gives rise to behavior and then natural selection.
  • adrian_b 6y ago
    "Genetic material" is memory. Therefore it must have the following properties: 1. It must be able to store any random sequence of symbols belonging to a certain set (e.g. any possible sequence of bases in the case of nucleic acids). 2. There must be a way to make identical copies of it (e.g. nucleic acid replication). (the previous 2 properties are true both for its own genetic material and for a foreign virus that does not have any use for a living being) 3. There must be a way to use the stored sequence of symbols to direct some process that is useful for a living being. (for nucleic acids, the better known useful processes are protein synthesis and the synthesis of certain kinds of useful by itself RNA, but there are also some other poorly understood functions of most of the "junk" DNA)
    • randallsquared 6y ago
      I'm not sure defining requirements by analogy is a valid process.
      • adrian_b 6y ago
        I do not understand what you have meant by "analogy". The 3 requirements that I have listed do not contain any analogy, they just give a precise expression of the conventional meaning of the words "genetic material" as applied to a component of the living beings, now known to consist of nucleic acids for the life on Earth. While not all biologists would be able to define precisely what they mean by "genetic material", the listed requirements correspond to the actual use of the word, in the most general sense.
        • randallsquared 6y ago
• adrian_b 6y ago
  It is pretty certain that the first life did not use any kind of genetic material, because that is impossible. When RNA or any other kind of genetic material first appeared, the first thing that must have been possible to do with it was to copy it, a.k.a. to replicate it. If the genetic material was used first to do anything useful, e.g. to control protein synthesis or to catalyze directly any useful reaction, that genetic material would have disappeared immediately, because it could not be replicated. So the first genetic material must have been able of being replicated without doing any useful function, therefore is was actually an RNA virus. The useful functions must have appeared later and then the genetic material was integrated as an essential part of the living beings, allowing a much faster evolution towards levels of complexity that would have been impossible to reach without having a genetic material. To be able to replicate the first genetic material, there must have already existed some life forms able to exploit an energy source to reproduce themselves. You have noticed a correct analogy, exactly like the control automaton of a CPU, which can be either hard-wired, having a dedicated structure that cannot be easily changed to perform other functions, or it can be microprogrammed, using a control memory, whose content can be easily rewritten to implement a very different CPU, a self-reproducing living being can use genetic material, in which case it can easily evolve into a different living being, or it may use no genetic material, but consist, like how it seems to be said in Gánti's work, of which I was not aware until now, by a cycle of reactions, where in each reaction some cell component assembles another cell component, until the last component, which assembles the first component. Such a living being, without a genetic material, could not evolve easily, because almost any change would have damaged the cycle of reactions, most likely stopping the reproduction. Regarding RNA, before the first RNA molecule was ever assembled, the existing life forms must have been using ATP and the other nucleotides as dehydrating agents able to condense smaller molecules into larger molecules, e.g. for creating peptide bonds. Therefore ATP (with some of it current uses) is certainly older than RNA. The polymerization of nucleotides into RNA must have been initially an undesirable side reaction consuming the useful nucleotides.
  • Ericson2314 6y ago
    Have you seen the research of Ribosomes being quine-like? (the structural nucleic acids and genes for the protein parts are related).
• marcosdumay 6y ago
  I think it's likely that the first life like our kind was only composed of genetic material. RNA and DNA are prone to replicating themselves (with many errors and not efficiently) in a wide variety of situations. It's way more likely that evolution selected those molecules for efficiency than that some complex life appeared without some transferable data storage.
  • adrian_b 6y ago
    No they are not able to replicate themselves, in any circumstances. Obviously, any RNA or DNA molecule can serve as a template for the polymerization of another nucleic acid molecule. However the polymerization cannot proceed spontaneously. The nucleotides polymerize by condensation, i.e. by releasing water. It should be obvious that such a reaction cannot be spontaneous when the molecules are already surrounded by water. You need some molecule able to extract the water from the nucleotides, for example an acid anhydride, like ATP. That anhydride must have also been produced by water extraction and in the water environment you need an energy source for that. So if you will complete the analysis you will reach the conclusion that you need an existing living being for the replication, no replication can occur otherwise. Obviously, in a lab you can yourself substitute the role of that living being, by providing adequate supplies of monomers and of energy sources, so you can replicate nucleic acids in abiotic conditions. Nevertheless, that could not happen in natural conditions.
    • marcosdumay 6y ago
      You seem to want life to appear in a likely condition, without some external power source. Whatever condition there was, it could as well be some extremely rare one, and I really can't imagine how some molecules could start to reproduce without their environment being constantly changed by some external energy flux. Besides, I'm no expert, but I don't think there were huge amounts of pure water running around on the early Earth. There were so much more stuff to use those hydrogen and oxygen atoms, and Earth's water wasn't all here since the beginning.
• cossatot 6y ago
  The crystal thing is throwing me (a geologist) off. Basically all Earth materials are crystalline. So rocks are alive (colonial organisms I guess since they are aggregates of crystalline minerals) but the magma that they crystallize from is not alive? Or is magma alive too? What about obsidian, which is glass but compositionally identical to a crystalline igneous rock. No crystals! The Earth's crust and mantle: Crystalline. Alive. The Earth's outer core: liquid iron and nickel. Non-living. The inner core: crystalline iron and nickel. Alive. Crystallization is reversible in a thermodynamic sense. You take some granite, melt it, and then cool it (slowly, under pressure), and you have granite again. Is this a phoenix/Jesus-like life and death cycle? Or does life only change forms? I agree with you generally that 'life' may be gradational. However I think calling crystals 'life' actually removes any meaning whatsoever from the term. If the line isn't somewhere in the neighborhood of viruses and prions then it kinda has to expand to include anything made of matter (and then energy etc.). While we don't (and don't have to) have a precise definition of 'life', the 'life' gradation needs to branch like a Bezier curve off the x axis at some point for it to be a functional term.
  • narag 6y ago
    Is key word "alive" or is it "conscious"? Or at least "sentient"?
    • whatshisface 6y ago
      Crystals are mostly not sentient, except for quartz. The high prevalence of quartz in the Earth's crust can be explained by the anthropic principle.
  • 6510 6y ago
    As the ancients knew: All facts require an observer so life is what can be convincingly be identified as life by a human being.
  • andrewflnr 6y ago
    Playing devil's advocate: "crystalline" in bulk is different from "a crystal". I think the idea is that individual crystals are "alive" in that sense, and the bulk is maybe a colonial organism. Maybe quartz crystals forming in a chunk of what will soon be granite are only "alive" in the brief period where they are still growing. When the rock solidifies, the crystal "starves" and "dies", leaving only a corpse. Melting and refreezing granite would basically be composting, using formerly alive material to foster new life. On a similar note, a dead human is "compositionally identical" to a living one, at least for a little while, so I think that's entirely a red herring. :)
• a9h74j 6y ago
  I am not sure we have colonized the minerals, but I am pretty sure we have been relying on fossil fuels as so-called "energy slaves."