Prions are formed by glycoproteins, don't have any n.a. (nucleic acid). I don't believe they're alive, as I'll explain later. I would also include in my theory of living things the proviruses wich (in accord with Temin) can evolve to retroviruses. It is, really, a difficult question, and that's the real point; because (and that's the original question of the thread) how can we say something is or isn't alive? Sure I mean something "organic" that fits some basic needs; and I think that the main think a "living" structure must do its self-reproduce, assure the continuity of the "specie", or, let's say, structure. Viruses are higly-arranged structures capable of replicating theirselves, that's why I think they're alive. Anyway, scientists all around the world don't reach an agreement on this point, so we don't have to agree about this. Just one thing; sorry about my english level!! Please Register or Log in to view the hidden image!
Why aren’t prions alive? Just because they don't have any DNA or RNA? What happens if we ever found aliens without nucleic acid? viruses can't replicate them self’s, cells do that for them. if a biological virus is "alive" then why not a computer virus?, both replicate.
That's everyting but science!. Let's say we find aliens without n.a., then we'll have to redefine our terms about life. But until that.... Please Register or Log in to view the hidden image!
and what about my other questions? I also disagree on your mythology it would be best to make a definition of life that is more inclusive and flexible. Saying it need nucleic acid and it replicates already exclude prions which replicate but consist of only glycoproteins.
Sorry dude, I didn't see the other question. You're right, cells replicate viruses for them, but that's the way they found to replicate. In fact, I can't replicate myself neither, and that's a fact. About the computer virus... this may be a new kind of life, 'cause sure, we all've seen those viruses doing their things in our computers!!! Please Register or Log in to view the hidden image! Now, seriously, we can't consider a computer virus alive 'cause it's a simple computer program. If you switch down the power of your computer it's world also disappears.
Why can't you reproduce, do you lack functional reproductive organs? Do your cells not undergo mitosis, do you not have gametes undergoing meiosis? A virus does not have a metabolic system it only has information which the cells automatically follows, a computer virus is the same thing it is only information which the computer (cell) automatically follows, Also shutting down your computer does not rid it of viruses, most computer viruses are stored on the hard drive, unless you make this analogy to destroying the computer would kill the virus, same thing happens if you lyses a infected cell (though the virus’s progeny escape freely)
When I said I can't reproduce myself I was meaning reproducing a complete, new, functional human myself, all alone. Sure viruses don't have metabolic systems but, would you say that metabolic routes are what differentiates an alive being from one not alive? The computer viruses are not alive 'cause they're not organic, and that, as I said before, is one of the things I believe that can differentiate a living being from a non living one.
I don't think you could find a alien that has no metabolic pathways, how could it move or think or do anything for that matter? It would just sit there and wait for something to input energy. And once you input energy it would have metabolizim. So life needs to be organic? what about robots what if you make machines that reproduce and evolve?
I don't believe in aliens, so I don't expect to find them anyway. But to answer your question, if (as you say) you can find aliens without nucleic acids, then why can't you find them without metabolic pathways?? Robots are not alive, this is not life, it's a pseudo-life generated by humans with complicated algoritms so they can "act" as living forms, but they are not. And thay can't evolve if you don't program them to do so. Or you think that a car-making machine is alive and it's generating it's offspring (cars)?
You could find aliens with some other means of heredity other then nucleic acid, but you could not find aliens that lack means of converting energy, that would break the laws of thermal dynamics. Humens and organic life are machines: we metabolize on pre-design pathways and carrying out instruction on genetic code, we evolve simply because our genetic system has a rate of error, I don’t see a difference between robots and organic life aside from complexity, robots could evolve if they reproduced, they don’t need to be programmed with evolution algorithms since any form of data storage has a rate of error. car making machines don't make them self and don't do so without human control, it would have to be autonomies of us before it could be alive.
So, yo say that thermal dynamics' laws cannot be broken in aliens (I also think so, but we're talking 'about impossible things, improbable things if you wish, so...), but you say that genetic's laws can, of course, be destroyed. Anyway, I think that talking 'bout aliens won't report us anything, just because we're talking about things wich, personally, I don't believe in. Even if you do, then you can't know how the hell they are, so this conversation will get nowhere this way. And you say: robots could evolve if they reproduced, they don’t need to be programmed with evolution algorithms since any form of data storage has a rate of error.. And with this I fully don't agree. You say that we (and as "we" I don't mean humans, I mean every single organic living being) evolve 'cause of the rate of errors in our genetic code and that it's some kind of true, sure, but now, tell me how can a robot evolve if (as you say) they could, at any time, reproduce. Explain me this idea so I can understand you better, 'cause I don't see how something whose behavior is just defined by programming, can evolve just because their data is sensible to error. You mean an error on their hard-drives will change their pre-compiled source-code?? Or let's say that their code is not compiled and they do it real-time, anyway, would an error on the hard driver change the source?? Sure I think we'll be able to develop robots able to reproduce themselves, 'cause this is not something so difficult (in fact, some nanotech "apparatuses" can duplicate themselves if they have a depot of parts of which they're made of) but evolving requires very special conditions in the hereditary material.
And when did I say such a thing? I was only proposing that life forms could have genetic mechanism other then DNA-RNA. First of all our behavior is defined by program, so already there is problem with your disregard of the robotics analogy. Second of all if you have a reproducing system (be it organic or not) with an error rate in duplication then Darwinian evolution is a must and will happen given enough time and environmental pressures. yes that exactly what I’m saying, do you doubt that a error in our genetics could change the shape of a protein to induce new functions and abilities?, that’s what your saying! It does not matter the how the data is stored, errors will provide mutation, a few mutations will be beneficial, the benefactors will prosper, ect. If organic machines can do it why not inorganic machines?
I don't believe all our behaviour is defined by program, im absolutely sure we are not "programmed" to be here in a chair, in front of a computer writing with a keyboard in a forum on a network of millions of computers all around the world. With that you have to agree with me. It's completely different. Robots are programmed with a computer, and the radical difference is that we have, in each and every cell in our bodies the exact copy of our "source code", our genetic code. We can "evolve" when we do a change in our codes (a good change, obviously). Robots cannot change their codes. No, that's for sure! If we didn't have a copy of our genetic code in every cell of our body, mainly in the reproductive cells, we wouldn't be able to evolve, 'cause we wouldn't have the possibility to change the code. False, this is the main difference, robots have no access at all to their codes.
No but we are programmed with impulses and basic instincts which manifest them self’s in more complex ways because of the thing we learn and adapt to. You’re typing on that forum because you like to, you like because it is an emotion, and emotion and pre-design. Mnay AI Robots run on the similar systems of negative and positives impulses and feed back. Many forms of AI robots do not need to be programmed, they run on FPGR (Field Programmable Gate Arrays), also these robots and many others can change their codes it call evolutionary Algorithms. I don't think you understand what I was saying protein structure and reproduction are totally different subjects. This is false many AI robot do, how else could they learn and adapt? I think you need to study Robotics and AI before you make ignorant assumptions. Refrence: http://www.aai.ca/conf/ http://www.aber.ac.uk/~icawww/Proceedings/paper-02/Icaris2002_paper2_final1.pdf http://crim.ece.ncsu.edu/projects/evolve/mckibben/ugrs.handout.pdf
FPGAs combine an ASIC ( Application Specific Integrated Circuit) with an user-programmable logic. You set the "logic" your robot will have. About the evolutionary algorithms, they're great, sure, I really think we're making much advances in the robot industry, but one thing it this, and another much much different is to equal this to the real evolution mechanisms. The examples you sent me (although I already knew of that) cannot (I'll say it again) be compared at all with real evolution proccesses, they're called this way, nothing else to do with them. A incredibly complex robot which can avoid the obstacles in it's changing environment it's something great, but we cannot say the robot it's evolving when it avoids an obstacle; it is avoiding an obstacle, not evolving. For sure I understood what were you talking about. You said me if I doubt that a error in our genetics could change the shape of a protein to induce new functions and abilities? and I said no. Our proteins can change 'cause we have a genetic code (the genetic code codes the proteins, remember?). What's worng with that answer?. One thing is the AI system and another the robot, sure they're connected and work toghether, but they're different systems, as you probably know. They don't have the source code of their AI systems, thet have the physical hardware, which they can change (read evolve if you wish, but I still say this is not evolving) in response to environmental changes. How you think a robot could change the code of it's AI system? It's all defined by rules you can control. It has nothing to do with our genetics, nothing. Well, I believe that you don't need to insult me to be right. Just try to explain me your ideas and try to convince me, but don't insult me, this won't help you here. One thing else, I would like to know what idea of the evolution you have, 'cause you may have some conceptual errors.
Re: a reply to river wind I agree. this assumes that the surrounding biological and non-biological environments remain stable between generation, which is usually not the case. The one who passes on the genes which are the most effective in dealing with the next generation's set of environmental conditions is the most successfull. Genetic success must be viewed with more that a single generation in mind. If I have 3,000 children, but all of them have sterile children, I am genetically a failure in the long term, despite my initial success. from the methods you mention. However, they are not incidental, they are integral. Many animals control their rate of nucleotide reproduction error more than others- this tells me that those who do not have checks to the same degree did not have an evolutionary drive to develope them. Therefore, the mutation rate seen in animals without extensive error-cheecking systems is as important to their adaptation and survival as reproduction itself. I do mix these things, and that is because that after years of biological study, I have come to the conclusion that in many cases, evolution has worked itself tot he point where the boarder between the well being of the parent and the well bein gof the offspring is very blurred. In many cases, the well being of the offspring *is* the well being of the parent, such as in many mullusc, fish, and insect species where the parent individual dies right after mating. What would be the purpose of mating if the individual was not going to die down the road? what would be the purpose of dying if an individual was not going to mate? After thinking about these two questions, it appears to me that death would not stand on it's own as a useful thing beyond the first generation without reproduction. Reproduction can stand on it's own two feet w/o death, but is not sustainable in that arrangement beyond a few generations (given a limited-reasource environment). Assuming nothing about why both things exsist, it is feasable that they both came about as evolutionary factors for the reasons I posted before. Unless Death from "natural cuases" is simply due to the body wearing down over time. However, studies over the past decade with mice suggests that this is not the case. Aging seems to be controlled genetically. I have studied these, but it was years ago. I'll read up on them again tonight, in case I have forgotten something important (it happens alot). thanks for the rebuttal! always fun to track down these thought paths! Please Register or Log in to view the hidden image! As for computer viruses and AI- I would say that they are not naturally alive, but that there is less and less noticably different between the two. As for computer viruses, I would say they would only count as alive if God exsists. Then both Computer viruses and biological life would have been created by intelligent being, with set directives. If God does not exsist, then I would say that computer viruses are not alive because they only reproduce because they were instructed to do so by their creator, with no reason or drive to do so beyond that. If I write a computer virus programmed not to replicate, then it won't. Biological viruses, according to my undergrad biology textbook, are cosidered alive only when they are activly infecting a cell (during reproduction). At any other time, they are not considered alive. That seems like such a logical strech to me, I feel that "life" as a word, needs to be re-defined. As was mentioned earlier, there was a time when cells were the smallest atom of life. I feel that we know anough now to say that cells are *not* the basic building block of life, yet for some reason, we refuse to let go of the idea. 1)incredably simple robots, based on insect design can avoid objects 2)adaptation ( on an individual level) and evolution differ by only two things: the scale on which they act, and the method through which they act. Adaptation on an individual level works through chemical memory (a simple shift in chemical pathways via an outside influence) or conscoius/unconscious memory. In either cases, an individual who can adapt best to its environment is the most likely to survive and reproduce. Evolution works on a genetic level within an overall population. However, it is still all about "who can adapt best to its environment is the most likely to survive and reproduce." "the individual" is just changed to "the species" No, a robot that avoids an obsticle is not evolving. But if it learns how to avoid that object, and remembers for later use, it is adapting. And if it can then pass that knowledge on to its ofspring by changing the offsprings basic form or functionality, then it's kind is evolving. If it passes that knowledge on without changing the physical or the programmable form/function of its offspring in some way - if it passes it on by teaching alone - then its kind are not evolving either. They are just collectively learning.
There are definitely other variations of 'living' things on other planets, I'm sure of it. However the "creatures" (if they are even like that) that evolved on other planets are probably completely different than us. They could be made entirely of a special energy, or some other form of matter we don't know about. Aliens aren't going to be meat,bones,guts, etc, just because WE are like that. Based on the environment of the planet, all sorts of "life" is possible. It's stupid to think life can only happen in ways that it has happened here on Earth.
Re: reply from 'developmental biology' http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?tool=bookshelf&call=bv.View..ShowSection&searchterm=volvox&rid=dbio.box.213#214
