Tibor Gánti's ideas about the origins of life(nationalgeographic.com) |
Tibor Gánti's ideas about the origins of life(nationalgeographic.com) |
Certainly there were lipid membranes. Maybe there were spontaneous proteins, maybe there was purely-catalytic RNA.
I guess it's also a matter of line drawing. I'm OK with calling crystals life, for example. One should feel bad about breaking up big ones the same as one should feel bad about killing 150 year old lobsters.
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.
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. :)
What do you mean? Bezier curves are 2d parametric curves, the x and y axes are completely arbitrary...
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.
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.
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.
Planet Earth would/should definitely count as alive, especially if it "reproduces" via us terraforming other planets to become like Earth.
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.
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.
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.
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)
“Life” as it were, is a concept invented with either the intention of distinguishing “us” from the rocks around ourselves, or, if you’re being slightly less charitable, giving “us” a way to insult the, um, others.
Sure, drawing some line in the sand between mice and boulders is a great idea, but it’s a pretty arbitrary one, especially if you have to strap a bunch of historical baggage on it.
This grand debate is almost as fun as what-constitutes-a-planet. We should do that one again.
Hence the current astrophysical paradigm where we now have planets and dwarf planets (which aren't planets).
When we do finally agree on a mathematically rigorous definition of life, it will seem obvious in retrospect and scientists will kick philosophers off the field, just like they did with previous subjects like the composition of matter, the movement of heavenly bodies, etc.
Every scientific topic has to go through a messy definition phase before its study can be properly organized. People studied heat and cold for a long time before they really knew what they were, for example.
(Also by phlogiston's time, philosophers and natural philosophers = physicists had already pretty much split.)
Or in other words, say at some point we discover aliens in a distance galaxy. Would we be cousins? Are there visualizations that show what that kind of family tree would look like?
I am a neophyte in this area but I'm sure there's a lot of good research out there.
And that's just the broad strokes, trees would be the details.
It's worth noting also that even only considering life on Earth that we already know about, the "tree of life" is already kind of a broken abstraction. Consider bacteria that are able to share genetic material without an ancestor relationship for instance, or closer to home even viruses that infect humans or any other kind of mammals. They affect our genetics in ways the tree doesn't/can't capture.
[0] https://physicsworld.com/a/amino-acid-detected-in-space/
Actually lipid bilayers are extremely complicated as they have to filter what gets into the cell and what doesn't, as well as what might leave it. Earlier systems might have done without them and instead attached everything onto long chain like structures... You know like a keychain. Both RNA and Proteins are long chains so maybe that's how they evolved.
https://en.m.wikipedia.org/wiki/Von_Neumann_cellular_automat...
> According to the chemoton model, life should basically, but of necessity, have an autocatalytic subsystem consisting of metabolism and a replication process, and a membrane enclosing these functions.
also
>A single chemical reaction is said to be autocatalytic if one of the reaction products is also a catalyst for the same or a coupled reaction
I was also going to point out the irony that the news article cares more about the man rather than the discovery of the origins of life.
There is no news here. This is just the same speculation that has been made thousands of times before for decades. Of course we can make big molecules from small ones in a lab. Of course life has to reproduce, metabolize and have a boundary from the environment. Pointing this out is not "the key to the origins of life". It is still an interesting topic, but why cant national geographic discuss these things honestly?
"The Revolutionary Phenotype is a science book that brings us four billion years into the past, when the first living molecules showed up on Planet Earth. Unlike what was previously thought, we learn that DNA-based life did not emerge from random events in a primordial soup. Indeed, the first molecules of DNA were fabricated by a previous life form. By describing the fascinating events referred to as Phenotypic Revolutions, this book provides a dire warning to humanity: if humans continue to play with their own genes, we will be the next life form to fall to our own creation. "I am VERY impressed with this book—very important topic very well treated." - Robert Trivers"
https://www.amazon.com/Revolutionary-Phenotype-amazing-story...
fyi: I'm not the author
And of course that this is the key to the origins of life - how could we possibly make progress on this question without understanding this first?
And someone had to be the first to point this out. Which Tibor Gánti did in 1971 & 1974.
>Some consider this model a significant contribution to origin of life as it provides a philosophy of evolutionary units.[4]
https://en.m.wikipedia.org/wiki/Chemoton
Read the wiki. Its just describing what a cell is and putting the word "abstract" in front of everything. It makes no prediction, it produced no results. Evidently not everyone considers it a significant contribution.
This is not self evident. Maybe this is the news?
I am not sure, what are you saying?
> organisms are open systems that maintain homeostasis, are composed of cells...
https://en.m.wikipedia.org/wiki/Life
Cell by definition have a boundary called the cell membrane.
>Cells consist of cytoplasm enclosed within a membrane...
Primitive proto-life has little moral value, just as vegans eat plants, hypothetical super-vegans only eat blue-green bacteria, and hypothetical hyper-vegans have a 500 year deadline to be electrically powered.
I don't believe in a hard barrier between life and non life, so any discrete moral function would be non-computable, and therefore I reject it outright.
That's not a problem. There can be insane theological and ethical consequences for everyone else.
If we take that life plausibly "started" as as one single-celled individual who then "reproduced" through cell division (let's call him Luca), then he's effectively never died - in the same way that we consider ourselves to have not died despite regularly cycling tissues and cells.
All life as we know it, if viewed like that, is one organism whose chain of cell division has never been broken as he's grown over billions of years. Variation between those cells (kingdoms, species, plant / animal etc) become like skin, hair and brain / liver cells within the human body.
It would be like taking a runner grass or banana tree and trying to draw a line around true individuals.
If we created life outside of that unbroken chain of cell division, we would have created something which is definitely "other than Luca" and that feels philosophically significant.
So no major consequences.
Edit : forgot about crystals that absorb energy while forming:
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.
Can you point me to a spot where it says that?
That's quite an assumption. I think there were 42 original proto-organisms spread over all the aeons. Creating a 43rd artificially is not a big deal.
Otherwise, I still think that it would be.
To clarify, though: I'm not at all against the creation of another individual.
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?
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.
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.
> "Genetic material" is memory. Therefore it must have the following properties:
A more precise wording of my understanding of this line would be:
> "Genetic material" is loosely analogous to memory. Therefore, we can derive what properties it has in physical reality by declaring what properties memory must logically have.
This makes it clearer what I was disagreeing with, I hope.
Otherwise the first ribosome would have disappeared soon after it was first assembled, without leaving any descendants.
The first ribosome was probably made only of RNA, as there were no other ribosomes to assemble the ribosomal proteins, so it is not surprising that at some point some of the ribosomal RNA segments were replaced by proteins transcripted also from some ribosomal RNA segments, if that happened to improve the ribosome structure.
For example we know for sure that all the chemical reactions required to assemble the components of a living being required the same amount of energy then as they require now, so either there was a source of energy large enough to enable them, or they were impossible.
Other things may not be completely certain, but they are overwhelmingly plausible, for example if we know that the transition from a more primitive structure to a more complex structure required 5 improbable mutations, we can be pretty sure that there is no chance that all those changes happened simultaneously, but they must have happened in a certain sequence, one by one.
If moreover, there are some causal links between those events, so that some of them cannot happen unless others already happened, then we may be able to determine which was the sequence of those 5 events, with considerable certainty.
While we are unable yet to estimate confidently which of many possible things really happened in the distant past, we can actually exclude with great certainty many other things, about which we can say for sure that they did not happen, because they contradict fundamental laws, like the conservation of energy.
Among these things that certainly did not happen are some previously popular theories about the origin of life, whose authors did not attempt to analyze them in enough detail to see if they are compatible with the known chemistry and physics, e.g. the ancient theory of the "organic soup" or the more recent theory of the "RNA world".
This route would be much more of a dance than what you’ve implied. A transient ribosome makes a protein-based RNA replicase, replicase copies all local the RNAs including the RNA ribosomes. This process would eventually result in a large number of ribosome RNAs and replicase proteins without the need to have a “perfected process” prior to either step.
The whole process would be much messier than what we see today after millions of years of refinement, of course. The stability of an arbitrary RNA polymer is also increased by the presumed lack of RNases as well.
It has been a few years since I took a grad course covering the ribosome, so excuse my lack of currentness if new research has discounted this.
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.
Nowadays however it is more widely believed that eukaryota descend from archea, but anyway it's pretty much a given that viruses are not and have never been alive. And while the opposite has happened, gene transfer usually goes from viruses to cells, endowing them with new abilities, more than the opposite direction.
I have an alternate theory, that I've never seen articulated elsewhere: Viruses might be inter-microbial biochemical warfare gone wild; Among primitive and not-particularly robust cells, one competitive strategy might be to package toxins or other disruptive molecules into capsids that cleverly get past the 'enemy' cell membrane, perhaps aimed simply at disrupting the initially brittle reproductive process. Packaging random genes in with these capsids would be the beginning of the Horizontal Gene Transfer function that viruses perform in the ecosystem. A refinement would be to add in the specific genes for producing capsids as a deliverable so a subverted 'enemy' then takes out several neighbors (but 2nd gen capsids don't have to necessarily contain the same genes in order to accomplish their 'mission', or even be entirely identical to the 1st gen, as long as they work). A further refinement would be increasing fidelity, and packaging the responsible genes into the 2nd gen capsids produced by subverted cells so the 'weapon' can spread exponentially.
And voila, the 'weapon' has now escaped the originating organism and can evolve independently parasitizing the target. Each incremental step can at least hypothetically provide an evolutionary advantage so the whole thing doesn't have to spring forth fully formed.
Depending on how widespread variants of the original strategy were, viruses might have independently emerged more than once.
If I'm right, we ought to still be able to find cells that attack or suppress competitors with capsid-like molecules that don't particularly resemble existing virus lineages, possibly containing non-genetic payloads of various sorts.
We might also find bacteriophage endoviruses that as their 2nd stage only produce capsids sans-genes or that otherwise aren't identical to the endovirus, or ones that aren't very good at packaging up the correct genes, or that are much better at disrupting cell reproduction than hijacking it, or that the subsequent copies are only low-fidelity ones that can similarly penetrate the host but not spread any further; basically any indicators that the mechanisms for penetration of the membrane, attacking the cell, and even for making poor 2nd gen copies, have been evolving longer than capabilities only needed for indefinitely repeated copying, retransmission, and reinfection.
I suspect though that the oldest reconstructible endoviruses will no longer be capable of penetrating current members of their host cohort, which tells us little about the virus itself, but may offer clues about whatever ancestral cells were still prone to infection were like.
Hosts do the replication for the viruses.
Environments do NOT do the replication for the fish.
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.
Very few things are obvious. Is this?
(When you feel compelled to “air quote” a key term in your argument, that’s a clue you probably don’t have a good argument.)
Earth+Life is a different entity than Earth on its own, or any other planet.
Earth allows and protects life, and life in turn influences Earth. That kind of symbiosis on such a scale is in a class of its own, with no other equivalent or analogy that we know of. It deserves a special classification.
Parts of yogurt are alive. Yogurt is not alive. I have no problem with this.
Life permeates deep into Earth and even influences its geology:
https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole#Resear...
Not really the same thing, but if alien life was found on Europe or Enceladus, religions would resist to change their theologies.
Unlike thinking there won't be consequences of importance because of a belief that < 1% of humanity even thought of maybe possibly having
Yes, this is what I mean. There is seemingly no organism/species that I would confuse whether to classify it as human or not human but I'm pretty sure there are species/organism albeit is rare that I would be in hard time categorizing it as cat or not cat.
Another example is human male and human female, albeit is rare but there is some human population that I would have a hard time deciding which category to put.
What is a human?
It might even be defined by social criteria, quite literally. Yet, Homo economicos is not the only social animal and not the only one with a social conscious either.
Actually, I think you want to talk about humanity as a whole, as an organism to draw a clear distinction, because the level of controlled organization is unparalleled.
In that sense I can agree with your sentiment, because I am not sure how much man's success is really controled and not just the result of sheer luck, despite horrible accidents and individual failure.
On another note, this isn't your websearch box. I went on to write an essay because I tried to take the question serious. This became invariably self centered and thus potentially dehumanizing to everyone else, trying to reclaim the terminus because failing to find an interesting definition which would rest on intricate topics in current research and traditional philosophy, I felt rather insecure, dumb and worried if a strong definition of humanhood would eventually exclude myself, whereas too weak a definition would have barely any utility to anyone. It is quite poetic, here's the climax:
"The collective memory greatly expands that capacify, so it can remain out of the question if an individual ape has a low mental capacity, if you won't ever find enough monkeys assembled around a typewriter as you can find humans in the market place trying to dictate the value of life."
To double down on that, let's say the appropriate question goes who is.... Whereas what rather goes along as relative pronoun to denote possession. What has a human, well, a typical human has many humans around them, above and below. Whereas a single human is practically dead, if not conserved in living memory.
Next up: Human rights for Artifical General intelligence and bionic hind brains for poor hackernews commentators, where to draw the line.
This is priceless))
Ideally we should clone enough to see if we can connect us and bonobos in a species complex (no hard boundaries of infertility).
I'm salivating over all the ethical choas that this would cause.
On the other hand, other forms of anabolism require crossing an energy barrier (and consumes energy) ?
While catabolysm is the inverse operation : crosses a barrier, but releases energy?
The formation/destruction of "exothermic" crystals like dissolution of Sodium Hydroxide if put in contact with water is I guess similar to above two reactions ? (Or better example: explosives)
That simply means "metabolism" isn't the concept to generalize further, and I'm OK with that.
It's recently became a loaded term (much like gender) due to people in general using the term like that. See expressions like "humane" or "transhuman".
I would prefer if they used some other word instead of overloading the method, but oh well.
Single cells of multi-cellular organisms replicate.
Shoot me in the head and all my cells will eventually stop replicating.
To a cell in my body, is the body a host or an environment? Is the distinction useful?
As for shooting into the head, some multicellular life forms can actually heal from that. From planaria you can remove any part of their bodies, it will grow back. Shooting into an ant colony won't do much harm to them either, nor is removing the branch of a tree. It's only a property of animals I'd say who have given up this property (for the most part) in exchange for more complex metabolic systems. (heart, nervous system, etc)
Mammals are the exception here, there the environment for replication is an integral part of the body of the parent. But in all those other cases, including, technically, marsupials it isn't.
An egg is a complex life that can reproduce the whole organism (and actually with energy stored INSIDE, that’s why they are great nutritios value for others)