Can you define life in three words?

By Carl Zimmer | January 11, 2012 9:59 am

We are all sure we know what life is, but if you try to actually define it, things get tricky fast. I wrote a feature about the scientific struggle to define life in 2007 for Seed, and I’ve been keeping tabs on the evolution of this metaphysical quandary ever since. I was particularly intrigued to discover recently that one scientist thinks he can define life–and do so in just three words. I’ve written an essay about his short and sweet definition for the web magazine Txchnologist. Check it out.


Comments (50)

  1. Fighting Thermodynamics (says the chemist)

  2. organically delayed entropy

  3. We could build a robot to self-reproduce with variations; would it be alive? Do viruses self-reproduce? If so, do prions? I would certainly not call the latter “alive”.

    I agree that the definition is probably “irrelevant”, at least to science, as Szostak says. In fact, I think a lot of attempts to define things are useless. To take this into the political/cultural realm, the definition of when life begins is thought by many to be the key to the abortion debate. But why would we think that there is a moment when life begins, rather than a continuum — like baldness? If you can’t define how many hairs make someone bald, why would we be able to define something more nuanced like where life begins, or — getting back to science — why life differs from non-life?

  4. Colin Bisset

    I like this one:
    That which communicates.
    Living things, consciously or not, recognize that others exist.

  5. rdiac

    Self replicating order. From Lyall Watson in the sixties. I’ve always assumed he nailed it however newagey he became – love to hear one more succinct.

  6. FastEddie

    Birth, work, death.

  7. Aung Aung Oo

    Matter and mind.

    [CZ: Tell that to E. coli…]

  8. John Moore
  9. Creation-Destruction Cycle

  10. cosmic self-recognition

  11. transferase

    I once heard someone smarter than me say that life adds information to matter, and I liked that so I’ll go with:

    matter + information

  12. Emyr Williams
  13. susan
  14. Entropy meets autopoiesis.

  15. Gil

    Robust imperfect replicators

  16. Michael Day

    Chaperone For Genome

  17. Carlos

    feed, mutation, evolution

  18. victor
  19. Chris

    Looking for s e x

  20. Alex

    Replicated replicators replicating.

  21. Sian Evans

    Too fucking short.

  22. Torbjörn Larsson, OM

    Biological evolution.

  23. Torbjörn Larsson, OM


    A biologist explained to me prions are too badly defined (complexes of proteins and calcium) to be live entities. In any case, the hereditary trait is a topological fold in a class of proteins, even if it jumps species barriers and so evolve.

    Viruses are certainly life, they evolve in an environment of cells, cells which in turn evolve in an environment _they_ are dependent on. Viruses are just very simplified parasites in most cases.

    In fact, recent research claim that Megaviruses (Mimiviruses for example) have evolved out of eukaryote cells that became early parasites on other eukaryotes. The encapsulated viruses is the simple egg, the adult virus factory inside an amoeba is as large and complex as bacterial cells.

    There is no hard and fast line between life and non-life. Or life wouldn’t be. Nevertheless it is easier to see this from the perspective of established life, evolution. There life is not a property of an individual but of a population (of metabolic network chemicals for chemical evolution or biological individuals for biological evolution.)

    The NASA definition of life (heredity and metabolism) is to simplify identification of individuals, but will fail in many or most cases. (Say, viruses – which are the most numerous populations on Earth.) Conversely, a lone sexual individual can never procreate, so are not sufficiently “alive”.

    To see individuals as life is too anthropocentric. Or egocentric. (O.o)

  24. Yacko

    Sucks, big time.

  25. Torbjörn Larsson, OM

    I looked through the article, and it will be interesting to cogitate on.

    My immediate reaction is that one would have to distinguish between a process definition (life as a product of the process of biological evolution) and a classification. Woolf has a Linnean classification of life in a SETI talk.

    The idea is that the NASA definition, or Trifonovs evolutionary definition, yields systems like hurricanes as alive. (Hurricanes can spawn structurally similar hurricanes, change when the environment change, et cetera.) So Woolf makes that the genus, while the species (“life”) is sufficiently diversified. IIRC he uses a description of genetics, but I may remember it wrong.

  26. Matt’s ” Fighting Thermodynamics” is my pick of the above, although it could better be rephrased as, in one sense, “fighting a losing battle against entropy”.

    The important point, anyway, is that it permits of the extension of “life” beyond biology.

    A concept dear to my heart. For there is considerable evidence that the life process can be traced at least as far back as stellar nucleosynthesis and detected in the evolution of, for example, geology as well the development of technology within the medium of shared human imagination.

    It can usefully thought of, overall, as the evolution of new atomic and molecular species.

    This may not seem to fit intuitively with the technological phase, particularly with respect of the fastest growing field of information processing devices. But looking more carefully, we find that the development of computer chips, for instance are utterly dependent on novel chemistry for their operation. In electronics and photonics, the fastest growing areas today, chemistry is the engine under the bonnet inconspicuously driving change.

    As with biology, new configurations of atoms make it all happen!

    The broad evolutionary model leading to such interpretations is outlined upon, in a very informal manner in “The Goldilocks Effect: What Has Serendipity Ever Done For Us?” . A free download in e-book formats from the “Unusual Perspectives” website

  27. Hmmm – I just realized that I did no, as requested, define life in three words.

    In the light of my previous post maybe I could just say “Evolution of Chemistry”

    Polemic, no doubt, and maybe incomplete, but c’mon, what do you expect for three words?

  28. dave chamberlin

    complexities best dance

  29. Joe Evans

    Learn, teach, repeat.

  30. Self-replicating metabolizing objects.

    Implies that viruses and prions are not alive, which is fine by me.

  31. Gary B

    From my systems science & artificial life classes: “complex adaptive systems”

    As a side note, I’ll argue that Rutherford was not completely correct when he said (something to the effect of), “All of science is either physics or stamp collecting.” I opine that “All of science is complex systems; physics and stamp collecting are special cases.”

    (Physics has concerned itself with the two ends of the complexity spectrum – ‘billiard ball systems’.)

  32. Gary B

    follow-up – I seem to have munched the last line of my comment, which should have been:

    “Physics has concerned itself with the two ends of the complexity spectrum –‘billiard ball systems’ where the number of components are few and can be modeled individually, and fluid/gas dynamics, where the number of components is very large and can be modelled best as a fluid body.”

  33. Bill

    My three words. respiration, copulation, expiration. Has a nice ring.
    However respiration, reproduction, expiration is more general.

  34. simon

    big cellular mass.

  35. lillie

    sleep with dachshunds.

  36. Executing non-molecular biosoftware

  37. Bill

    f(f) = f

    or less cryptically

    metabolism(metabolism) = metabolism

  38. David B. Benson

    “Into the Cool”

    Its a book title, yes, but the book is about life and thermodynamics.

    [But maybe Bill @42 has best summed it up.]

  39. The molecular gene concept is scientifically untenable. It is violation of chemical principles. The Quran reveals that life is non-material phenomenon validating the original proposal of nonphysical gene by Wilhelm Johannsen in 1909. He warned against two things while proposing the gene concept; one is against treating gene as material entity, and the other is against assigning gene for particular character. Both his warnings have been now proved correct.
    The nonphysical biological information can be conceived on the lines of computer concept of the organism. Phenomena of life and death can be defined and explained in the light of the Quranic revelation based on the computer model of organism. The Quran informs that nonphysical rooh (or nafs) is the cause of life and its removal (deletion) from the body results in death. In the computer model, the chemical structures (including DNA) from cells through tissues to organs constitute hardware of the organism. The nonphysical rooh is the biosoftware of organism. The computer software is also nonphysical although it requires a physical medium (disk) for storage. Similarly biosoftware also requires a physical medium for its storage. The hard disk of organism is chromosome. The invisible software is the soul of the computer as the rooh is the soul of an organism. As the deletion of rooh causes death, deletion of the software also brings the computer to halt. A dead body is like a computer without software. Based on this reasoning, life can be defined as the manifestation of execution of divine biosoftware in body, and death as the result of its deletion from the body. This assertion based on the Quran is falsifiable. It predicts it will be impossible to create life from non-life without using a living cell or organism at any stage of the process. It also predicts that a dead cell (or dead body) cannot be restored to life. In fact a dead cell has all the material structures including DNA intact at death. But yet the cell doesn’t show any sign of life. This itself shows a chemical structure (material) does not constitute biological program. All the experiments to create life from non-life going on at various centres in the world are destined to fail proving that molecular gene concept is the costliest blunder ever to commit in the history of science. Biologists can as well prove their idea of material gene by bringing a dead cell back to life by chemical means since dead cell is comparable to prosthetic cell. They don’t have to create genome or cell from scratch chemically, which is not feasible without involving living cell or organism during chemical synthesis. For detailed discussion please see posts 4 and 5 at my blog

  40. Life in three words?

    Payment of Original Sin

    (Cash, please!)

  41. (Sorry, I am going out of topic here, with a particular question to the post above.)

    Mr. Wahid, I have seen your profile at your blog and think that you are a good man for Humanity. Thirty years of research experience in perennial crop nutrition – loll, it is a good job. Thanks for existing. You know that Humanity is in trouble and need urgent solutions, so, any force that avoid Humanity going far away off the beam focused on the search for solutions is not good for human kind. Sorry, but your post suggests in my single opinion, that after you retired you are unconsciously being used and applying a force not good for human kind. Each phrase from yours has no proved foundation on reality or cannot be grasped by the human reason built by Nature. What is happening?

    You are propagating a theory, which can be influential to students, then, we are competitors because I also have a theory that I think is better for students, called “The Universal Matrix/DNA of Natural Systems and Life’s Cycles Theory”. As competitors we will fight for the space through debating the details of ours theories. Ok? Let’s go?

    Your theory: The molecular gene concept is scientifically untenable.
    Matrix/DNA: I don’t know any proved fact showing it its wrong. Then, it is an opened falsiable theory, requiring investigation. If your antenna is not opened for all possibilities, my suggestion is cleaning it, because the most cause are wrong beliefs attached to the antenna as dust. Look if the antenna is not pointed to only one direction; it must have arms pointed to all directions.

    You: The Quran reveals…
    Matrix: “Wait, please. The Quran? Who is/are/were the person revealing it? Which real fact, which experiment, he/them showed in the way that I can repeat it?”

    You: “… validating the original proposal…”
    Matrix/DNA: “Wait… Proposals, theories, are not the objects under focus. They are process of human thoughts. Any human thought obey evolution through the mechanism of life’s cycles. In a human life’s cycle the shape of teenager is transformed into the shape of adult. You cannot have the two shapes at the same time. So, in the evolution of a human thought, the external stimulus is the spermatozoon, the idea is the fecundation, the theory is the teenager, the real knowledge in the shape of a natural law, for instance, is the adult. At the momentum that something is really known (adult), the theory (teenager) already does not exists. The thoughts of Mr. Quran can validate the thoughts of Mr. Johannsen? Maybe only in the realm of thoughts, not in the realm of the object. If Mr. Quran did not show the experiment, it is a theory, and a theory does not validate another theory… Ok for me it is enough. I am seeing we will not have a conversation on this issue about life’s definition.

    But I was looking your website. The idea of the Universe working as a computer (hardware + software), is interesting because my theoretical models are suggesting the same thing. But I am layman about computers. Then I have questions:

    You: “The Quran informs that nonphysical rooh (or nafs) is the cause of life”.
    Matrix/DNA: “What came first in computers: the hardware or the software? First I thought that was the hardware that began with the “abacus” , but the abacus was made from a necessity in the human mind (the origins of the computer software). But the human mind was a product from the hardware human body. Really I have no resource for proving that the life of the bacteria that evolved to humans was caused by this software or the opposite, the software was caused by the bacteria. Do you have? How was the diagram of your suggested alien software that developed the first cell’s system?

    Ok. Looking from this perspective, I think that the comparison of life with computers makes no sense. But, my resulting models from my calculations continue suggesting the comparison. They show a single diagram of software existing at the primordial soup, coming from the matter of non-living world. Then I was looking at your website the mention about which software has you or Mr. Quran detected in the primordial soup or, at least, a theory of the software inside our ancestors astronomical or atomic systems, and you have not inserted it. Could you, please, show the diagram?

  42. ojcrush1221
  43. P.A. Wahid

    Mr. Louis Morelli, sorry for the delay in responding to your comment. The molecular gene (genome) theory tells us that the genome constitutes the biological program responsible for the development of the phenotype and biological functions performed by an organism. In other words, the program encoded by the genome structure is the driving force of life. It is based on this assumption, studies are now carried out to create life from nonlife. The scientific community considers an organism as mere bundle of molecules and there is nothing nonmaterial in it. What I say based on the Quranic revelations is that the divine biological information (biosoftware) is not encoded by any chemical structure but is nonmaterial (nonphysical) stored on the chromosome like information (e.g., software) stored on computer disk. What the chemical structure encodes is divine chemical information which is manifested in terms of physical and chemical properties, and behaviour of the molecule. Molecular biologists say DNA structure (the only molecule in the whole universe) additionally encodes biological information! This is wrong. By that assumption, they are superimposing biological information over chemical information. The computer model of organism on the other hand clearly distinguishes the two kinds of information. We know the chemical structure of hard disk (material) of a computer does not constitute the software but the software (information) in the computer is stored on that material (chemical substance) taking advantage of its properties. Computers, robots, etc., which run on man-made programs, are forms of ‘artificial life’. Answers to your questions are given below.

    1. You said about molecular gene concept: “I don’t know any proved fact showing it its wrong. Then, it is an opened falsifiable theory, requiring investigation.”

    The original proposal of the gene made by Wilhelm Johannsen in 1909 was ‘nonphysical gene’. But the scientific community was not comfortable with a nonphysical entity perhaps because of its divine connotation. With the discovery of the role of nitrogen bases of the DNA molecule (as codon) in the determination of amino acid sequence in protein synthesis and following the elucidation of the double helical structure, DNA came to be known as the blueprint of life as it is supposed to encode biological information. Thus Johannsen’s nonphysical gene metamorphosed into material gene in the 1950s. Molecular gene was born that way. Today molecular gene concept is in a ‘do or die’ situation although scientists may not accept it. It may be recalled here that Johannsen had cautioned against perceiving gene as physical entity and also against assigning gene for particular character. Both these warnings have now been proved correct. Fogle observes: “Today, in the era of genomic sequencing and intense effort to identify sites of expression, the declared goal is to search for genes, entities assumed to have physical integrity. Ironically, the sharper resolving power of modern investigative tools make less clear what, exactly, is meant by a molecular gene, and therefore, how this goal will be realized and what it will mean” (Fogle, T. 2000. In Peter Beurton, Raphael Falk, and Hans-Jörg Rheinberger, The Concept of the Gene in Development and Evolution. Historical and Epistemological Perspectives, Cambridge University Press, Cambridge, pp. 3-25). Horace Freeland Judson (Nature, 2001, 409:769) notes: “The phrases current in genetics that most plainly do violence to understanding begin “the gene for”: the gene for breast cancer, the gene for hypercholesterolaemia, the gene for schizophrenia, the gene for homosexuality, and so on. We know of course that there are no single genes for such things.”

    The role of determining the amino acid sequence in protein synthesis is not enough of a criterion to describe DNA as the molecule encoding the genetic information of an organism. Amino acid sequence is not the whole story of life. Even here it fails. There are DNA molecules (non-coding or the so-called junk DNA) that do not encode that information. The genome of the dead body is identical to that of its living counterpart. But yet it does not show any sign of life. What happened to the biological information encoded by the DNA in the dead body? All that we attribute to DNA molecule are, in one way or the other, violations of chemical fundamentals. We cannot explain any of these anomalies based on chemistry. For a detailed discussion of the inadequacy of molecular gene, please see post 4 at my another blog

    2. You said: “Wait, please. The Quran? Who is/are/were the person revealing it? Which real fact, which experiment, he/them showed in the way that I can repeat it?”

    The pathetic plight of modern biology is the best proof of the validity of my theory. The reason for the current plight of biology may be traced to the erroneous concept of gene. Biology is the science of life but biologists are unable to define life. Molecular gene is the fundamental basis of biology but molecular biologists are unable to define what molecular gene is. Dozens of ‘theories of origin of life’ have been proposed but none of them tells us how life arose. Yet they all go by the name ‘theory of origin of life’. Species is the unit of evolution but evolutionists do not know what ‘species’ is! Without having any idea of these, can we say biology is on the right path? On the other hand, the computer model of organism based on the Quranic revelation of nonphysical biosoftware explains all these and more. Please see my blog If it is possible to explain the phenomena of life and death based on this theory, is this not sufficient proof for its validity? If one wants experimental proof that is also there. The theory of nonphysical biological information or nonphysical basis of life, which I proposed, is also scientific theory as it is falsifiable. Scientific evidence of my theory comes from the failure of molecular gene theory. The validity of the nonphysical basis of life can be confirmed from the prediction that it will be impossible to create life from pure chemical substances via chemical synthesis without involving living cell or organism at any stage during the experiment. That will unambiguously confirm my theory, which in turn will prove the divinity of the Quran and existence of God because it is based on the Quranic revelations, I proposed that theory. In fact biologists are poised to prove that through failure of molecular gene theory. It is just a matter of time they realized it is impossible to create life from nonlife (i.e., from chemical information).

    3. You said: “What came first in computers: the hardware or the software?

    Please see post 5 on my blog that discusses creation of species through programmed evolution. It may be pointed out here that even without an iota of evidence for the origin of life from chemical molecules, biologists adopt that line. But you do not question that. My theory considers the term ‘origin of life’ as misnomer; it should be ‘origin of biological information’. It is the advent of biological information on the earth that marked the origin of life on the planet. We have to distinguish chemical information from biological information.

    4. You said: “I think that the comparison of life with computers makes no sense.”

    It only makes sense. Thousands of journals publish papers in areas relating to molecular gene, origin of life, evolution of species, etc., regularly over the past several decades. Yet nothing worthwhile is known about life. This reflects the uselessness of the information based on molecular gene to define life. It also proves that all that is published in journals is not science or credible information. Phenomena of life and death can be defined and explained only in the light of Quranic revelations based on computer model of organism. Please point out the reason why my definitions of life and death are not correct. One of the important differences between artificial forms (e.g., computer, robot, etc.) and natural forms (i.e., organisms) of life is that the biosoftware of the latter also carries information for reproduction.

    I accept your challenge and am prepared to debate on my theory of nonphysical basis of life with you.


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.

About Carl Zimmer

Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The LoomHe is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.


See More

Collapse bottom bar