2307: Alive Or Not
|Alive Or Not|
Title text: Computer viruses currently fall somewhere between prions and fire.
There is no universally-accepted definition of "life"; all definitions thus far proposed have either excluded some things commonly understood to be alive or included some things commonly understood to not be alive. Take reproduction, a trait commonly assumed to be essential and unique to life; by this definition, anything which cannot reproduce (including mules, worker bees, and postmenopausal women) would be considered nonliving, while anything which can duplicate itself (including computer viruses, advanced 3D printers, and fire—see below) would be considered alive.
Many more elaborate definitions of life have been attempted over the decades. Some common additional factors include:
- Homeostasis, the ability to control an internal environment to maintain a constant state;
- Metabolism, converting nutrients into energy and building blocks for growth, reproduction, and so on;
- Adaptation through heredity and natural selection; and
- Responding to the environment.
Despite all of this, the only definite definition of "life" is "something everyone agrees is alive". This comic attempts to rank several types of things by how likely people are to perceive them as "alive".
Things ranked as alive
- Animals (normal)
- Animals (weird ones like jellyfish and coral): Randall's categorization of animals as "normal" or "weird" is a simplified version of the Great chain of being, a philosophical framework in which humans are seen as the most "advanced" form of life, followed by a divine or otherwise justified hierarchy of progressively lesser life-forms (mammals, birds, fish, lizards, insects, and so on). Categorizing weird animals was already done in 1587: Food Rule. Alternatively, corals can be considered as lying between animals and fungi because corals, like, fungi and plants, are sessile, i.e., they "grow" in one place. Jellyfish are not sessile, but many jellyfish are the same species as corals in different generations.
- Fungi: Fungi represent a unique lineage of eukaryotic, mostly multicellular organisms. Although historically studied by botanists specializing in the sub-discipline "mycology", modern scholarship places fungi in the "opisthokont" lineage, which contains both the animals and the fungi. Fungi, like animals, cannot make complex organic molecules from carbon dioxide, and must consume organic molecules as food to survive. Like plants, fungi are typically unable to move on their own. The various types of fungi include mushrooms, yeasts, rusts, smuts, and molds. Fungi evolution is also referenced in 1749: Mushrooms.
- Plants: Those often green, often leafy things outside your current isolation dwelling, sometimes inside, next to the window. They are primarily distinguished from other eukaryotes by being able to use photosynthesis to convert water, carbon dioxide and energy from light into sugar and free oxygen.
- Slime molds: Slime molds are eukaryotic single-celled organisms (so "more advanced" than bacteria). In the "plasmodial" slime molds, the "single cell" may expand to spread across several feet of territory, and weigh several pounds, while the "cellular" slime molds are most notable for their occasional congregation into macro-sized colonies which can appear to move as a single creature. It's interesting that Randall ranks them as "less alive" than fungi (which they were once thought to be), especially given some of their curious behaviors (e.g. optimizing transportation networks when presented with a collection of food flakes and obstacles).
- Bacteria: Bacteria are one of two groups of prokaryotes, meaning cells that do not contain a nucleus and rarely harbour membrane-bound organelles. A small portion of Bacteria are pathogenic, but most are actually harmless. Bacteria's ability to convert raw materials into nutrients available for other living things makes them essential to other living things.
- Archaea: Archaea (misspelled as Archea by Randall) is a domain of organisms, which do not fall under eukaryotes or bacteria. They are single-celled organisms that lack a nucleus, and were initially thought to be ancient lineages of bacteria (i.e. archaeobacteria) found in extreme environments similar to the early Earth, which is probably why Randall ranks them as "less alive" than bacteria. However, it is now known that they live pretty much everywhere that regular bacteria do, and that they have very distinct biochemistry from bacteria; they are actually more closely related to eukaryotes (i.e. slime molds and up) than bacteria are.
- Viruses: Viruses are infectious agents consisting of a genome surrounded by a protein or lipid shell. When a virus contacts a cell, it delivers its genome inside the cell which causes the cells' reproductive machinery to create more viruses. Since viruses are incapable of reproducing without the aid of larger cells, it is often debated whether or not they are actually alive. Randall has ranked viruses as "alive" but on the lowest possible rung of such; indeed, many biologists say viruses fall in a gray area, or that the question is arbitrary and non-scientific. By another criterion life on Earth is defined by the presence of extremely long molecules that can be replicated (copied). Every organism above viruses contains both DNA and RNA. Viruses only contain either RNA or DNA. Nothing below here contains any (biologically active) DNA or RNA.
Things ranked as not alive
- Prions: Prions are misfolded proteins that cause other proteins to misfold. They are most famously the cause of various brain diseases such as "mad cow disease", and may be involved in Alzheimer's disease. Similarly to viruses, prions require something else to replicate, but unlike viruses, they do not possess a nucleic-acid genome or any other means of carrying heritable information, and they do not alter the cell's production machinery, but rather interact with proteins which are already made. In that sense, they're more like a particularly tricky kind of metabolic waste product or pollution.
- (from title text) Computer viruses: A piece of code which hijacks computer systems to replicate itself, named by analogy to biological viruses. Strictly speaking, they're just a particular encoding of information, usually stored in electromagnetic media (although there's no reason one couldn't be stored on punch cards). Randall ranks them as "currently" more alive than fire, because they do carry "genetic" information (which anti-virus programs can be programmed to look for, analogous to vaccination) and some are capable of modifying themselves to adapt to new environments, but less alive than prions because they only operate within information systems. However, if a virus were able to e.g. hijack an electronics factory to start making flash drives and memory cards that carry the virus's code, then perhaps it might move up in the hierarchy.
- Fire: Fire is a common example of something which meets many common definitions for life; it grows, reproduces by spreading seeds (sparks), and consumes energy and excretes waste (ashes and smoke) by the same net chemical process as respiration. However, while fire can be a necessary part of the life cycle of other organisms (e.g. redwood trees), it does not maintain a constant environment within itself, nor does it perform anabolism, the construction of larger molecules from smaller ones. Respirating life-forms use helper molecules to moderate the oxidation reaction into small steps to produce useful units of energy, rather than letting it all happen at once to produce heat.
- Clouds: Random shapes taken by clouds may resemble animals and other objects, but arguably they are not alive in any sense. Things like tornadoes and hurricanes, on the other hand, can meet some definitions of life: they maintain homeostasis, actively seek and consume energy, and occasionally reproduce. Cf. Fire above.
- Fossils: Fossils are the petrified remains of once-living organisms, so in that sense they are more connected to life than "regular rocks", and some may hold DNA that could theoretically be used to clone the fossilized life-form.
- Rocks shaped like faces: Humans have an extremely advanced capability for seeing patterns, and one of the most powerful patterns we seek is faces, so much so that we see faces even where they don't exist (a common form of pareidolia). Humans instinctively anthropomorphize any object which vaguely resembles a face as having a sense of attention and mood, and so a rock shaped like a face would likely be treated differently than a rock not shaped like a face. Randall does not distinguish between rocks intentionally carved to look like faces (such as the famous Moai sculptures) or rocks that happen to look vaguely like faces under the right lighting conditions (such as the famous Face on Mars.)
- Regular rocks: Modern taxonomy originates from Carl Linnaeus, who categorized all objects on Earth as animals, plants (often stated as "vegetable" in quiz games like Twenty Questions), or minerals. Minerals are most obviously not alive, although some cultures and works of fiction have creatures that turn to stone and will return later to life, and some people keep rocks as "pets".
Interestingly, the vertical line linking the categories extends beyond both the most-alive and least-alive things, making one wonder what Randall might think is more alive than "normal animals" or less alive than "regular rocks". In the latter direction an explanation might be that shortly before this comic the scientific press wrote about heat-resistant bacteria that live in the desert and slowly eat regular rocks generating their own water in this process making even the sand in the desert partially alive.
- [A chart consisting of vertical line, with 14 dots and a horizontal dashed dividing line drawn across the list a bit below the middle. Each dot has a label to the right of the line with a line pointing to the dot they belong to. Above and below the dividing line is a label with a broad arrow pointing up above and down below.]
- Up arrow: Alive
- Down arrow: Not alive
- [Dot labels from top to bottom above the dashed line:]
- Animals (Normal)
- Animals (Weird ones like jellyfish and coral)
- Slime molds
- [Dot labels from top to bottom below the dashed line:]
- Rocks shaped like faces
- Regular rocks
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