Prions Evolve Despite Having No DNA 214
An anonymous reader writes "Scientists from the Scripps Research Institute have shown for the first time that 'lifeless' organic substances with no genetic material — prions similar to those believed responsible for Mad Cow disease and similar, rare conditions in humans — are capable of evolving just like higher forms of life. The discovery could reshape the definition of life and have revolutionary impacts on how certain diseases are treated."
genetic material (Score:3, Insightful)
Prions are proteins that, like viruses, replicate via a host cell. All the high-level principles of evolution by natural selection apply; it's just the low-level mechanisms that are quite different.
Re:genetic material (Score:5, Interesting)
Putting the perils of terming new knowledge "obvious" aside, it does seem obvious that evolutionary mechanisms would have to be preexisting for life to have indeed evolved. Since the most generic definitions of life I've seen boil down to providing some form of localized reverse entropy, evolution of the materials of that reverse entropy should be able to happen before the condition itself is actually achieved.
To draw an utterly meaningless comparison, you can certainly have a power supply without a computer, but good luck doing any computing without the power supply. If that makes sense. I should probably cut my breakfast rum down to under 5 shots.
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Why would that be likely? (Score:2, Informative)
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Sure?
"From plasma crystals and helical structures towards inorganic living matter
Abstract. Complex plasmas may naturally self-organize themselves into stable interacting helical structures that exhibit features normally attributed to organic living matter. The self-organization is based on non-trivial physical mechanisms of plasma interactions involving over-screening of plasma po
Re:Why would that be likely? (Score:5, Interesting)
Why *wouldn't* it be likely?
Darwin of course knew nothing of DNA, and his theory of evolution says nothing about it. Darwin didn't put it this way, but the key requirements for an entity to evolve are:
1. The entity contains the information needed to replicate (self-description)
2. This information is subject to random changes (mutation)
3. The environment is hostile -- some but *not all* entities will be destroyed (survival)
4. Variations between individuals make them more or less likely to survive (fitness)
DNA-based life fits these restrictions, but so do entities which store their self-descriptive information in RNA, protein, or computer memory. It places no restrictions whatever on the existence of life chemistry based around other atoms than carbon.
You can make lots of chemistry arguments about why carbon is necessary, but you can't argue it on pure Darwinian grounds. As for your specific point in favor of carbon:
Carbon has lots of free valences, which allow it to act like a universal lego-block
Silicon has the same valence properties, and also forms a wide variety of complex molecules [wikipedia.org]. Phosphorus and sulfur can have valences of 5 or 6 in certain situations. Now, carbon *is* special, but not in the way you've described.
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Re:genetic material (Score:5, Interesting)
You're correct. If they evolve, they HAVE genetic material; it's a bit of a tautology.
It might be noted that, before the 1950s, biologists generally argued that DNA couldn't be our "genetic material", because it's structurally too simple. The most widely suggested storage for this sort of information was proteins, because they are the most complex chemical structures in our bodies.
This hypothesis turned out to be wrong. But there's still an old hypothesis that in the early stages 4 billion years ago or so, the early "living" things on our planet were mostly based on proteins. It's hard to come up with good tests of this, though, because RNA and DNA don't fossilize well, and we have no samples of them older than 100 million years or so.
In any case, this story is really just about finding some evidence supporting the protein-based inheritance conjecture. It's apparently valid to some degree in our modern world. It might be more widepread than just prions, but we don't know.
Something that we have known, and which was summarized well by Douglas Hofstadter in "Gödel, Escher, Bach" [amazon.com], is that our DNA doesn't actually contain a definition of the mapping of DNA to amino acids. That is done by the proteins that "transcribe" RNA strings into the amino-acid strings for the proteins. It would be possible, by doing a bit of swapping around of the active parts of those RNA-reading proteins, to use a different DNA -> amino acid mapping, and a few variants of this mapping are known in nature. The real complexity comes about from the fact that our DNA contains genes that produce the proteins that do this transcription. But without the already-existing transcription proteins in a cell, there would be no way to discover the mapping that we actually use, because the information isn't actually in the DNA. It's "distributed" between the DNA and the already-existing proteins in the cell.
Of course, such multi-factorial causation chains (with feedback) are far too complex for most of the media, even the scientific media. So we pretend that our DNA contains all the information needed to produce us. The biochemists have known for some time that this isn't really true, but they don't make a point of it, because it "would just confuse" most of the reading public.
OTOH, Hofstadter has had pretty good sales of his book. Any nerds or geeks here who haven't read it should do so. It'll teach you a lot of fun stuff about the extreme complexity of the universe we evolved in.
(Religious people who don't believe in evolution shouldn't bother. The book isn't really about evolution per se, but it'll still get you seriously upset or confused about the nature of the universe. ;-)
Evolution for creationists. (Score:4, Funny)
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Shame I don't have any mod points right now. That comic strip is quite funny and more on topic than off.
The creationists are a little more clever than (Score:4, Insightful)
Re:The creationists are a little more clever than (Score:4, Funny)
"I believe in micro-evolution but not macro-evolution"
"I believe in centimetres, but not metres"
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"I believe in micro-evolution but not macro-evolution"
"I believe in centimetres, but not metres"
More like, "So you claim I'm standing in my "house," and that it's 20 meters high. Well, if I squint I can see a centimeter of housey-stuff here, and a centimeter of housey-stuff there, and I do in fact live here, but there's no evidence of this large structure you call a "house"!"
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We have evolution (as in new traits being developed) of plants and bugs due to selective processes. We have evolution of bacteria through adaptation to environment and relative advantage. We observe differentiation of species through ring-species. We can recostruct the evolutionary links between speecies through DNA evidence. We have a pretty, consistent tree of evolution extracted from fossyls. How difficult is it to look at the big picture and say that evolution s the most probable explanation?
If anything
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We have a pretty, consistent tree of evolution extracted from fossyls. How difficult is it to look at the big picture and say that evolution s the most probable explanation?
I've never looked at the fossil record. I think evolution happens because the math makes it work that way. But, yeah, from what I've heard the fossil record is pretty overwhelming.
But Creationism is mostly an exercise in denying evidence. You can't very well carry the fossil record in your pocket, and if you're simply debating they have enough false claims that refuting the all means you can only draw even in the minds of the audience.
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And if you take them through a thought experiment such as a dog that goes in the water a lot, develops webbed feet over generations, then it starts spending all its time in the water, etc etc... they still call it a dog even though a macro change has occurred.
They simply don't want to admit they are wrong.
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And now, for the car analogy: "I believe that that gizmo allows you to go from San Francisco to LA, but you'll never get from San Francisco to New York.
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Wow, just because creationists are wrong doesn't mean you have to be so blatant about suppressing them.
They happen to be right on this point: proof of natural selection is not proof of evolution as a whole. The Doonesbury comic got that wrong.
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That's not the interesting part of this. First of all, prions were never consider life. They are not even nearly as complex as viruses, and no one really thought there was any kind of hereditary mechanism in what amounts to a relatively simple protein structure.
What it does tell us is that where there is replication, there will be adaptive and evolutionary processes.
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Pre selection: 90 black cats (BB) and 9 white cats (ww)
Post selection: 1 black cat (BB) and 9 white cats (ww)
Pre selection, the blac
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Actually, if the black gene is dominant and you have a closed system that kills all black cats then you will end up with a population of only white cats.
Dominant traits means that the dominant form of the gene masks the recessive trait. This means that if black is a dominant trait then a cat that has any amount of the black trait will be black. Thus your machine will kill every cat with that trait and there will be no cats with black traits to pass on to their offspring.
Here's a diagram to show this:
BB x WW
That's how (Score:2, Insightful)
That must be how the Crystalline Entity [memory-alpha.org] came into being.
Evolution is the good news ... wait, bad news? (Score:5, Insightful)
Natural selection doesn't pre-suppose DNA. Anything which multiplies to produce copies of itself, which can degrade/mutate between generations can evolve just in exactly the same way. Selection pressures work exactly the same. So does the chain reaction effect of multiplication of the survivors, resulting in major shifts in characteristics of a population.
But the actual story is the bad news part of it. That using anti-prion medication probably won't work all the time as it would just breed a drug-resistant breed of prions by preference.
Definitely bad news. We can forget about having the "saviour" take a bath in the daily oatmeal for our protection :)
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And iterative improvement based on external definition of 'improvement' (in other words, selection) doesn't presuppose either 'natural' or 'self'.
Cars evolve. Societies evolve. And so on.
Life is defined by metabolism & self replication, not evolution.
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You're right. However, whether prions evolve or not has no influence on their classification as (non-a)live matter.
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The pop culture definition may be overgeneralizing, but not by much. Looking at markets, there really is a lot of copy and paste and mutate in the way business models and such are formed. People think they know how they run a business, but most of the time it's pretty mindlessly sticking to a formula.
When you really look at it, people don't think very much at all. We almost inevitably copy how someone else did something and tweaked it a bit. Even if you carefully work something out using mathematical reason
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Definitely bad news. We can forget about having the "saviour" take a bath in the daily oatmeal for our protection :)
Once again, it seems the only way to get rid of a disease is by aiming at its total eradication and extinction like has been done for smallpox and like is almost done for polio.
Re:Evolution is the good news ... wait, bad news? (Score:5, Insightful)
using anti-prion medication probably won't work all the time as it would just breed a drug-resistant breed of prions
Not necesarily. Unlike the changes available for lifeforms with their own DNA, there is probably a finite number of ways a given human protein can degrade into a replicating prion configuration. Most proteins probaly have no capacity for becoming prions. For others, the body is perfectly capable of dealing with them.
The capacity to become a prion is already built into the structure of the host protein in question, not aquired through exposure. So while this evolution is probably real and possibly a stumbling block for therapies, it remains confined to the space of potential configurations already inherent in our proteome, of which only a very small subset will cause trouble as prions.
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Clever, but misleading (whether or not it was intended as a joke).
Darwin's theory of natural selection requires an entity to store the information needed to make *more* of itself. You can't make more matter -- at least, not without making an equal amount of antimatter -- so no natural selection is possible.
Not Surprised. (Score:5, Insightful)
It's time we recognized that the interesting things about "life" are all just products of the fact that all kinds of systems can convey self-replicating entities of some sort, and they tend to be interesting and undergo evolutionary processes and etc. Whether they are non-biological DNA bundles, cellular organisms, oddly folded proteins, crystalized clay, etc.
So where are the nefarious / useful engineered prions at?
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I don't think fire is a lifeform even though it is self replicating, can die, moves and grows on its own, and reacts to outside forces (and may attempt to consume it).
Re:Not Surprised. (Score:4, Informative)
Fire has a symbiotic relationship with some plants in Australia. The plants help start fire. The fire kills the plants competitors, including other plants and humans.
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Yes, the plants tend to be dry, oily, and highly flammable, with fire-resistant seeds. In the U.S., manzanita and similar plants are thought to do the same thing.
However, this has no bearing on whether fire is alive. Symbiosis is not a requirement of life, but (I think) evolution by natural selection is. Fire doesn't contain information about itself -- its properties are only a function of its fuel. It's not like lighting paper with a match produces a different fire than lighting it with a candle. Fire
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You might look into the Southern Pine, then. Before people showed up and started "improving" things, the Southern Pine would shed lots of flamable needles that would build up, and cones that wouldn't release their seeds until AFTER being heated in a fire. Then they counted on a fire every few years, which would wipe out the competition.
(Southern hear means the southern US. Places like Georgia.)
P.S. Last I heard the Southern Pine was in trouble, but I haven't followed it. People tend to object to forest
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Interesting thought on that. I remember an old episode of _Sliders_ where they ended up on a world in the midst of a big fire, and accidentally brought some living (and intelligent) fire with them to the next universe. I got into a discussion (funny, I can't remember who it was with anymore) about what things would be necessary to actually have living fire. In other words, what additional things would fire need to have to be considered living and how could it be achieved in nature. We covered a lot of groun
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That's what cellular respiration is all about. It was an interesting discussion and, in the end, a lot of it depends on points of view. That of course is the problem. You don't think fire is alive because you know that fire isn't alive and if someone comes along and tells you that fire is now included in the scientific definition of things that are alive, you'll disagree, just like lots of people are still pretty upset that Pluto isn't a planet anymore. If you examine what is and isn't alive in enough detail, the boundary gets fuzzy enough that it becomes harder to know where to draw the line rather than easier.
Yes, and that's where I think the summary gets it wrong. It talks about the definition of life, as if there's only one (probably the one that the author learned in grade school -- "respiration, reproduction etc.". As James Lovelock points out, "If we ask a group of scientists 'What is life?' they will answer from the restricted viewpoint of their own scientific disciplines. A physicist will say that life is a peculiar state of matter that reduces its internal entropy in a flux of free energy, and is charact
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We already have intelligent living fire.
Did you consume hydrocarbons today? What about carbohydrates? (Stuff with hydrogen and carbon in it, at least)
Did you inhale oxygen and exhale carbon dioxide? Did you somehow got rid of dihydrogenmonoxide or did the / a / one of the girl(s) block the bathroom the entire morning? :) - and did you emit heat while doing so?
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Interesting example, but I don't think that fire reproduces in a cycle where any instructions (genetic material) are ever created and used.
A fire is more like one simple entity that grows until it consumes all available food and then dies of starvation.
The alternative is to consider that combustion is a process that all life forms use. It has evolved into you.
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It's time we recognized that the interesting things about "life" are all just products of the fact that all kinds of systems can convey self-replicating entities of some sort, and they tend to be interesting and undergo evolutionary processes and etc. Whether they are non-biological DNA bundles, cellular organisms, oddly folded proteins, crystalized clay, etc.
It goes further than that - almost everything that is built is a product of evolution. Bicycles, planes, cars, the computer, have all been subject to the process of evolution. The fact that they can't self-replicate does not mean that the evolutionary process isn't present. No life can replicate without the necessary supporting environmental conditions, and if one of those prerequisite environmental conditions happens to be the presence of humans and amounts of refined steel and other materials, how is this
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I don't see a need to get spiritual about it (Score:4, Interesting)
Even from a purely materialist perspective, it seems reasonable to ponder a class of materials that replicate themselves. How exactly they do so might be more or less complex but the basic idea that it's possible to configure matter in a way that it replicates itself doesn't seem that absurd. And there's no particular reason it has to be DNA --- there are even purely mechanical possibilities [wikipedia.org].
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Rolling rocks "evolve" to roll better. A fire "evolves" to burn better. Water in a container "evolves" to fill a new container when it is placed in it.
There's nothing new about the ability for systems to undergo changes that make some actions easier for elements of the system. That's the whole point about evolution in organisms, it'd be surprising if it DIDN'T happen. Things that are successful tend to continue, things that are a dead end tend to stop. Any process that continues over a long period will tend
Okay, lets get redefining then... (Score:2)
If I glanced correctly at this [scientificamerican.com] article, which does ramble on, prions are rogue proteins which aren't just detrimental to the organism, but cause other proteins to mutate as well. It wasn't clear to me if they do this by altering the genetic code or the neighbouring proteins directly.
The host organism may apparently have DNA of such nature that a random mutation reliably triggers the disease symptoms. This indicates to me that the code molecules exist in a higher energetic state and them getting upset makes
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The theory is that prions are not neccessarily mutated but "misfolded" proteins, and they can provoke the same misfolding in neighbouring twin proteins by chemical bridging much like what happens when enzimes do their stuff. The misfolded proteins cannot be digested and precipitate, causing neuronal death. Because each prion turns many proteins like it into prions, their effect grows exponentially.
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For most of us, "unnatural" really means "disgusting to me". There's nothing natural or unnatural. As long as something occurs within nature and following its rules, it's natural. The "natural" thing is some kind of 'argumentum ad verecundiam' fallacy.
Evolution doesn't equip any being at all. It just works if the non-equipped are killed before breeding or if the equipped are better breeders.
Scrapie or CJD are normally ocurring and normally fatal. In the case of CJD, the mean age is around 65 y/o: long after
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Don't forget IV drug abuse.
Where does Death Begin? (Score:5, Interesting)
Not really related, but it is entirely possible for humans to be "alive" in a physical sense even after they are brain dead. As long as they are hooked up to respirators etc., they can be kept alive indefinitely. To date, no human being is ever known to have regained consciousness after brain death.
The _big_ catch here is that most physicians are not properly trained to test for brain death. Most physicians will just see a flat line on an EKG and declare the patient brain dead. I used to work at an organ transplant center, where there were technicians that went through a formal checklist to make sure the patient really is brain dead. It was not uncommon to find patients who did not meet the strict criteria. In the most dramatic example, a 3-yo boy was supposedly brain dead, and he was in the operating room, ready to have his organs removed. The technicians discovered that his pupils did respond to light, so they rushed him out of the OR. On the way back to his room, the boy opened his eyes and smiled. But then he went back into a coma and died 5 days later.
Needless to say, the boy's parents were furious.
Re:Where does Death Begin? (Score:5, Informative)
Here are the criteria for brain death. An in the case of children, they must be consistent with repeatedly flat EEGs throughout 48 or 72 hours depending on the place. Also, barbiturate and BZD intoxication must be ruled out.
* Unresponsiveness
o The patient is completely unresponsive to external visual, auditory, and tactile stimuli and is incapable of communication in any manner.
* Absence of cerebral and brain stem function
o Pupillary responses are absent, and eye movements cannot be elicited by the vestibulo-ocular reflex or by irrigating the ears with cold water.
o The corneal and gag reflex are absent, and there is no facial or tongue movement.
o The limbs are flaccid, and there is no movement, although primitive withdrawal movements in response to local painful stimuli, mediated at a spinal cord level, can occur.
o Apnea Test: An apnea test should be performed to ascertain that no respirations occur at a PCO2 level of at least 60 mmHg. The patient oxygenation should be maintained with giving 100% oxygen by a cannula inserted into endotracheal tube as the PCO2 rises. The inability to develop respiration is consistent with medullary failure.
* Nature of coma must be know
o Known structural disease or irreversible systemic metabolic cause that can explain the clinical picture.
* Some causes must be ruled out
o Body temperature must be above 32 C to rule out hypothermia
o No chance of drug intoxication or neuromuscular blockade
o Patient is not in shock
* Persistence of brain dysfunction
o Six hours with a confirmatory isoelectric EEG or electrocerebral silence, performed according to the technical standards of the American Electroencephalographic Society
o Twelve hours without a confirmatory EEG
o Twenty-four hours for anoxic brain injury without a confirmatory isoeletric EEG
* Confirmatory tests (are not necessary to diagnose brain death)
o EEG with no physiologic brain activity
o No cerebral circulation present on angiographic examination( is the principal legal sign in many European countries)
o Brain stem-evoked responses with absent function in vital brain stem structures
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The huge failure here is, to have this pointless urge, to draw a line between life and death. There is none. It’s a gradient!
Just like there is no separation between intelligent and dumb. Or between alive and dead when you ask if something is a life form.
The wish to draw a line is purely a human artifact.
But if you start to ask: How much alive is something? Or: how much of a life form is something? How intelligent is it?
Then you start get answers that are useful and make sense.
Now all you have to do,
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Furious about the almost organ harvesting?
Or furious about having to pay for 5 more days in hospital?
The idea isn't surprising (Score:2)
After all there's nothing "magical" about DNA. Any self replicating molecule should theoretically be capable of evolution if the replication process is less than perfect.
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After all there's nothing "magical" about DNA.
Except that it's a "better" replicator. DNA must have evolved from something. Given a few hundred million years, these prions might evolve into something similar to DNA.
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I'm skeptical (Score:3, Insightful)
I'm not quite sure I would call it evolution. I can easily imagine that many prions replicate not only themselves but variations as well and those variations will produce variations of different proportions and so on and so forth. So just because you subjected a prion to an adverse environment for a particular copy of a prion only means that form will be less populous.
It feels to me that this is less evolution and something more akin to chemical computation. Although ironically it does in some ways remind me of the poorly labeled Conway's game of life.
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I would say with certainty that it's closer to chemical computation than it is evolution. Prions' and proteins' function is heavily influenced by their shape. Their shape isn't a 100% consistent. So you could have an d shaped protein and a b shaped protein and they might still function as intended, but if it switches to an a shaped protein, it may not work anymore. Errors in folding are quite common, even in biological systems. Usually the aforementioned system has things in place to deal with prions,
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Matter. (Score:2, Insightful)
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Evolution is a large-scale byproduct of adapting to the changing environment in such a way that is energetically favorable for the organism.
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This is what happens when you start taking anthropomorphism seriously. You get grand-sounding philosophical statements ("Matter has a mission", "nature abhors a vacuum", "information wants to be free" (woot flamebait!)) which have no basis in fact (see Magsol's spot-on reply in this thread).
Re:Matter. (Score:5, Informative)
Any matter has one mission and one mission only: to find greater order. If matter without DNA or any prior form of order couldn't achieve more order, then life would not exist. Things want to be able to interact with their environment more efficiently, and must evolve to do so.
All things in the Universe try to minimise the amount of energy they have. In some special cases, like crystals for example, this means becoming more ordered: the energy of each atom/molecule depends on its distance from its neighbours, with each "preferring" the lowest energy distance. Getting as many neighbours as possible at this distance is effectively packing spheres with that distance as their radius, which turns out to be the most efficient with ordered arrangements like hexagonal close packing, so that's what's observed. In the general case, however, the amount of order goes down, see http://en.wikipedia.org/wiki/Entropy [wikipedia.org] . In fact, in every situation which becomes more ordered over time, Thermodynamics says that somewhere else there must be a system becoming even more disordered (as an example, if a system is minimising its energy by becoming ordered then it's exothermic: the energy its losing will come out as heat. This heat is itself disordered, and can disrupt the order of whatever it comes into contact with (which is why so many Physics experiments are done as close to zero Kelvin as possible). Also, the total energy such systems manage to lose is restricted by the fact that they are becoming more ordered, there is an "entropic cost" when becoming more ordered, which means that it requires energy to do and therefore the system must keep hold of that much energy to do it.
For a simple example of how becoming more ordered takes energy, try stretching an elastic band. The polymers it's made of would, in a totally disordered system, take "random walks", which is very degenerate (there are LOADS of ways to randomly walk a certain distance starting at a point A and ending at a point B is the distance AB is much shorter than the distance you walk, ideally A and B are in the same place). That's the band's preferred state, and as such it isn't particularly long. By stretching it, the distance AB goes up, so there are fewer random walks of the same length which satisfy these new positions. In the extreme case the distance AB will be the same length as the walk, and there would only be one valid random walk between them (ie. going in a straight line). It takes energy to stretch the band because you're making it more ordered, which it doesn't want to be.
If matter's mission is to find greater order then a stretched elastic band would never snap back ;)
Do Life and Evolution always go together? (Score:3, Insightful)
For example people talk a lot about the evolution of ideas, societies, and so on... Quite possibly, the philosopher Wilson is one of the popularizers of this approach.
Anyway, this also leads to a different point - Evolution by itself is not a proof of the existence of Life. For example, Ideas or Societies are not living organisms, yet they do evolve.
So the fact that prions evolve does not mean they are alive! One can fairly say that they are just a chemical (a protein) that can reproduce itself, evolve, and do damage.
In Science, Mathematics and Philosophy, it is very common to take "edge cases" in order to better understand the limits of an idea. Prions give us a good example of something that can reproduce and evolve, yet its a chemical not a living organism.
So what is "Life" ? Perhaps we should require the ability to perceive - awareness of ones surroundings - in order to define true life? In that case Bacteria aren't alive either, which is fine by me.
Jellyfish and Lizards do qualify as alive. More generally, you would need some sort of functioning nervous system (however primitive) to be "alive". Brain-dead people would possibly not be "alive" by this definition.
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"So what is "Life" ? Perhaps we should require the ability to perceive - awareness of ones surroundings - in order to define true life? In that case Bacteria aren't alive either, which is fine by me. "
Wow, that is simply the most pathetic attempt at creating a human-centric definition of life Ive seen... and Im a biologist, so Ive seen plenty of strange ideas.
There is not a single form of life that that is completely isolated from its environment. Animals, plants, fungi, bacteria, viruses, prions (I tend to
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Scratch that, theres one fact thats even better to make you think a bit about life: a human body is composed of TEN non-animal (bacteria, "protozoa", fungi...) cells for every one "truly living" human cell. So, were just made up of 1 part living stuff and the other 10 parts are non-living crap?
A bacterial cell is on the order of 1pg, whereas human cells are around 1ng. So they're on the order of 1% of your mass.
You've probably got more non-living mass in your gut and colon if you haven't taken a good dump lately.
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The best universal definition of life: (Score:2)
A (bio)mass, fighting for resources.
(If you raise the point, that that would include remote-controlled robots: Well yes, we control them, like limbs. And we live.)
Not New: Hypercycles (Score:2)
Not new. See
http://en.wikipedia.org/wiki/Manfred_Eigen [wikipedia.org]
"In addition, Eigen's name is linked with the theory of the chemical hypercycle, the cyclic linkage of reaction cycles as an explanation for the self organization of prebiotic systems, which he described with Peter Schuster in 1979."
Evolution doesn't require DNA, and the theory is like 40 years old at least.
Duh (Score:2)
Any system that can self replicate can evolve. Period.
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Any system that can self replicate can evolve. Period.
Unperiod.
Replication and evolution are mutually exclusive.
If it's a copy, it's not evolving.
If it's evolving, it changes.
Reperiod. Duh^2.
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In the real world replication is never perfect.
Reperiod.
Self replicators are self replicators (Score:2)
Sometimes they occur in the organic chemical domain using DNA. Other times not.
Same invariant properties apply:
1) Self-replicators take resources from their environment in order to self replicate.
2) Mistakes sometimes happen in self replication. Sometimes they enhance replication. Usually not.
Salt crystals in solution, YouTube videos, DNA, Money, Religion. It's all pretty much the same, structurally.
Is this being taught in universities yet, or have they not caught up?
Redefining Life (Score:3, Interesting)
In "Energy Flow In Biology" Harold Morowitz posits that an open system between an energy source and an energy sink, containing such elements as can form a variety of bonds and forms, will absorb energy, and form compounds that will persist in that state for a time in inverse proportion to how much energy is required to maintain the state. Increasingly complex forms can be created from those simpler forms if they persist long enough. Those more complex forms can have variations in their subunits locations and forms relative to the components from which it is built. This is the first chapter. The rest of the book is a bit of physics and a great deal of physical chemistry showing why the proportions of organics found on Earth as inevitable given the conditions of the Earth's environment and the combination of elements from which is is made.
The evolution part applies to the first chapter though. Some compounds self-catalyze, producing more. Some catalysts form that produce other products, but only do so when the first of those products form. Variations such as radicals appearing in different places on a benzene ring produce different forms, and catalysis can cause this to happen step by step, forcing the radical to 'march' around the ring.
Increasing complexity, with variations in forms of those increasingly complex forms, each of which have more or less ability to contribute to furthering these phenomena, that pretty much describes what life does. Maintaining itself at a level of complexity above the environment (read that 'maintaining itself in a state of negentropy) for a time, using the incoming energy, described something much like how life appears in contrast to its environment.
Again, this is all based on physical and organic chemistry, pre-biology. It's only logical to expect the activities of living things to mirror the activities of their non-living constituents. No, those compounds are not alive, but if they couldn't do those things, neither could life.
A marker then for life might be detection of compounds that carry out some functions we see in life, and an environment that allows them to increase in amount and in complexity. Where then do we put the dividing line between life and non? If we can objectively define and predict an emergent property that appears at a certain point in the growing complexity of the chemical soup that is characterized by a behavior which is necessary for life but is absent in the pre-living material, we might be able to describe that sufficiently to say it's one definition of life.
If it hasn't occurred to you before, it should now: a different environment and collection of compounds might also produce organics (or the equivalent based on other elements) will produce different results. If life, that will be different. Taking the definition from one situation is hobbling yourself when it comes to discovering other forms of life. It might also occur to you that there is no time scales associated with any of this. If we then take the broader view and don't limit 'life' to the result, but include it in the components, we can at least start with a statement about a component being 'alive enough to consider that aspect'.
We need as broad a view as possible so we will be able to recognize it when we see it elsewhere. A part of science is dedicated to looking for it. With our present definitions, which should be stated "Earth-like life" rather than simple "life", we are primed to not detect any forms of it which we could imagine but which differ significantly from Earth forms.
Article good, summary bad (Score:3, Insightful)
I didn't understand how they could be surprised that prions evolve, so I checked with the original article. They weren't. They were interested in the rates of evolution and the persistence of strains that were selected against. Quite reasonable.
Even totally inorganic matter evolves, in a rough sense. At it's basis evolution just asserts that those forms which are most suited to an environment tend to persist in that environment. This seems quite hard to challenge. Then it accepts Malthus computations on population, and asks: Given that it's obvious that not all descendants can survive, what does the two laws in combination imply?
N.B.: Darwin didn't know ANYTHING about DNA. Genetics hadn't yet been recognized. (This was after Mendel, but long before he was discovered.) So the basis of evolution clearly CAN'T depend on those facts. Evolution is really quite simple, it's just the working out of the details that is complex. (Just as Boolean logic is quite simple, but it's a long and complex way from Boole to a compiled program written in C.)
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im in ur prions
redesigning them
-- God
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Dear Sir, what does God need with a cheezburger?
Re:Surprising? (Score:5, Insightful)
It's a little more complicated than that. There's basically three properties that are both necessary and sufficient for evolution to take place.
* Some sort of fitness function
* Reproduction, largely based on the properties of the "parent"
* Imperfect reproduction, so that variation can be introduced
Once you've got those three items, you have the potential for evolution.
That said, it should be pretty obvious that basically any frequently-duplicated structure in the physical world, whether it be made out of DNA, protein, or metal and gears, is going to have all three of those items - the third just thanks to the physical world being imperfect. Note that it's not required that it be capable of duplicating itself - if all machines were built by copying older machines, we'd get to see "machine evolution" as people tended to copy the ones that worked better and throw away the ones that didn't.
Of course it's also worth pointing out that none of these requires that the item exist in a physical sense - you can meaningfully talk about memetic evolution, societal evolution, language evolution, joke and humor evolution, so forth ad nauseum.
Re:Surprising? (Score:4, Insightful)
Yes, prions do not reproduce through the conventional genetic mechanisms. From my understanding, they encourage, through some direct protein-protein interaction, other polypeptides to fold incorrectly.
Think of it this way. HIV and other genetic disorders propagate through normal reproductive means. Like, if a person with an extraordinary innate musical ability has a child, that child will probably possess a natural ability for music.
However, if a talented musician adopts a child and then teaches him how to read music and how to play instruments, he will probably grow up to be equally talented.
Prions are similar to the latter case. They are encouraging other proteins, who don't in themselves possess any malicious function, the fold in such a way to attack the host.
This isn't reproduction. The "parent" prions are not in anyway responsible for the actual formation of the "child" prions. They are just responsible for causing them to become malicious, making them more role-model proteins than actual parents.
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I agree - it is important to get away from the concept of evolution as being life-based, and recognise that evolution is an emergent property of a system.
For the prion example, the key is to remember that incorrectly folded proteins accumulate and cause the prion disease - the proteins themselves are not the disease, but the accumulation is. If one folding configuration is more likely to cause other proteins to fold incorrectly, then it is natural to assume that this configuration will become eventually dom
Re:Surprising? (Score:4, Insightful)
But that's exactly my point. It doesn't matter how the formation occurs. If the "parent" can reproduce, in any way, from construction to repurposing to just hanging around the "child" until the child starts acting like the parent, then it counts as reproducing. It's not like I have memes sitting in my head getting pregnant - their "reproduction" is that I say something funny to someone, and he remembers it, and says it to someone else.
Evolution is in no way restricted to lifeforms that can self-reproduce. Prions have a way to duplicate their important properties - their bizarre folding - and that's all that's necessary.
(And yes, role models can be a form of reproduction.)
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No, that would actually be a variation of intelligent design.
Regardless, it seems to me people here are confusing the everyday use of the word evolution with the actual theory.
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No, it works in a evolution sense too. Machines exist in an environment which is hostile to "broken" machines. It just so happens that their survival and reproduction is mediated by an intelligent agent, but the process is the same.
Domesticated animals follow the same pattern. They're evolving within an environment whose rules of survival are set by humans. Humans didn't "intelligently design" cows, in the sense of directly choosing specific mutations to lactation hormone receptors, we just set up a sel
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So machines (a new life-form) have evolved in a symbiotic relationship with humans? Perhaps Ford Prefect was correct when he took cars to be the dominant species.
Re:Surprising? (Score:4, Insightful)
No, this isn't what I mean. The vast majority of devices are built by understanding the concepts involved and designing a new machine off those concepts. If we, instead, just measured a machine that already existed, then built another one to those approximate specs, over and over again, you'd see designs that were slightly "better" flourishing while designs that were slightly "worse" dying out. Thus, evolution.
Re:Rocks Too (Score:5, Insightful)
Hasn't this bullshit "claim" been dredged up enough already? It's just a bit of really weak sensationalism from an attention-whoring geologist.
He himself doesn't even believe this nonsense, and does say, towards the end of that article that obviously "being changed by your environment" has nothing to do with "evolution", but hey, why not get some free publicity?
Re:Rocks Too (Score:5, Insightful)
But you’re no better. You insult the other side, and bring no arguments to the table. You’re obviously right... to us... but to them, you now just made it worse, making them protect themselves from your pointless attacks even more.
This time, I’ll do it for you:
The difference is, that Rocks have no fitness function. Which is the difference between undirected change and directed evolution.
But the next time, if you wanna act superior, bring an argument. Like a common basis, and proper logic on top of it.
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Precisely. It should be patently obvious to anyone with a functional brain that rocks to do not evolve. If you know what evolution is, and you know what rocks are, you should immediately recognize this.
This is different than, for example, disagreements about abortion. There, you're arguing matters of opinion and philosophy, what should be, what is right and what is wrong. Here, you're talking about what is, and the basic definitions of common words. Rocks change, but they do not evolve. The word "evol
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Precisely. It should be patently obvious to anyone with a functional brain that rocks to do not evolve. If you know what evolution is, and you know what rocks are, you should immediately recognize this.
No, sorry. Not precisely.
Making assumptions of how anything “should” be obvious, is just arrogant and fails precisely at the point I mentioned:
To bring arguments to the table and put them on a solid common basis.
You can’t ever expect someone else to blindly accept your assumptions. Or else there would be no point in using arguments, because one could just blindly state something, and insult the other person because “it’s patently obvious”.
But your comment did exactly that
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No flames can kill prions.
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Slashdot really needs a "+1 flamebait" moderation option.
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The Grand Canyon is also the result of evolution.
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It ate all of the Not-So Grand Canyons?
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"it's late, i'm over tired and maybe i should have cooked that last brain i ate"
Cooking won't help. Prions aren't alive*, cooking them won't kill them.
* depending on your definition of life, of course.
A.
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I'm sure that enough heat*time will do it, but I suspect that your food isn't food at that point. Autoclaving is insufficient to destroy prions on surgical instruments, for instance.
A.
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If there's a difference, your post didn't explain the difference. In fact, your post seems to suggest you don't have the foggiest idea what evolution is. I know looking skeptical can be cool, but it's only cool if you start from a position of knowledge on a topic. Otherwise, you just look stupid.