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Life: off topic continuation of " So linguistic time "

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Life: off topic continuation of " So linguistic time "

Postby daivid » Mon Apr 08, 2013 6:01 pm

Paul Derouda wrote:
Scribo wrote:I think the only difference between this and SMGreek is that it has a surviving infinitive form, I'd wager that some prepositions take cases other than the accusative but that's about it. Obviously its not actually ancient in terms of phonology, morphology, syntaxis, semantics and so on. But people will bite at anything and hopefully this sort of stuff brings her more funding. I mean...seriously Archaeologists always make the most ridiculous claims to chase funding and attention so she might as well.

But the most ridiculous claims must still be in space research. When you read the papers, you're really supposed to think that the big issue is whether there's life on Mars, or Titan, or wherever. Now that's ridiculous!

Life on this planet is remarkable to the extent that it is more or less programmed by the same code. To find a bacteria like organism would tell us a huge amount about what the possibilities of life are, the chances of it evolving elsewhere and the constraints that have shaped the evolution of life here. To say that is not the big issue is itself ridiculous.
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Re: Life: off topic continuation of " So linguistic time "

Postby Paul Derouda » Mon Apr 08, 2013 8:14 pm

Of course if we could find life elsewhere on our solar system it would be tremendous. But how extremely unlikely is that? To me seems sort of obvious that all those guys are just trying to find out basic information about the geology of Mars or whatever, the usual scientific stuff, primarily trying to find out things just for the sake of increasing knowledge. I think we know already for sure that Mars is a dead piece of rusty rock. But somehow I got the feeling that everytime somebody finds something even remotely interesting or surprising they're yelling that they maybe might have found something that might point that there was perhaps slight traces maybe of bacteria on Mars a billion years ago. Yeah sure.

I'm not saying that trying to understand the geology of Mars isn't important, on the contrary, I'd like to know more about that and less about the very unlikely prospects of finding life there. And I'm not saying there can't be life elsewhere, only not likely on our solar system.

Like you say, we don't really even know what life is, we only know one sample. How great it would be to know more! I just don't want to be over-optimistic about finding it next door.
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Re: Life: off topic continuation of " So linguistic time "

Postby Scribo » Mon Apr 08, 2013 9:19 pm

I like the unknown, honestly if we were to find an alien civilisation with thousands of years of history and literature I'd jump ship in about ten seconds.
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Re: Life: off topic continuation of " So linguistic time "

Postby daivid » Mon Apr 08, 2013 10:48 pm

Paul Derouda wrote:Of course if we could find life elsewhere on our solar system it would be tremendous. But how extremely unlikely is that? To me seems sort of obvious that all those guys are just trying to find out basic information about the geology of Mars or whatever, the usual scientific stuff, primarily trying to find out things just for the sake of increasing knowledge. I think we know already for sure that Mars is a dead piece of rusty rock. But somehow I got the feeling that everytime somebody finds something even remotely interesting or surprising they're yelling that they maybe might have found something that might point that there was perhaps slight traces maybe of bacteria on Mars a billion years ago. Yeah sure.

I'm not saying that trying to understand the geology of Mars isn't important, on the contrary, I'd like to know more about that and less about the very unlikely prospects of finding life there. And I'm not saying there can't be life elsewhere, only not likely on our solar system.

Like you say, we don't really even know what life is, we only know one sample. How great it would be to know more! I just don't want to be over-optimistic about finding it next door.


Having read your post I'm feeling guilty about calling your point of view mistaken and I hope you put that down to being too hasty in hitting the send key.

I also agree the geology of another planet is very important and for the same reason. The science of geology is based on one sample. To understand how it plays out, completely independently, elsewhere would be awesome.

Nonetheless....
*Life on this planet seems to turn up pretty much everywhere, even in the most unpromising places - places almost as unpromising as Mars seems to be.
*Life on this planet appeared very quickly almost as soon as it stopped being molten. This does suggest that like is likely to develop spontaneously as soon as conditions are even passably okay and hence some form of life should have arisen on other of system's planets/moons. But of course, as we have a sample of one, it could be a fluke. Should we fail to find life anywhere in our solar system after having looked everywhere then that in itself would be an important result. The very early appearance of life on earth would then begin to look like a fluke.

The place I'm watching, however, is not on Mars or Titan but Europa with strange red within the ice cracks and the gravity induced earthquakes providing a potentially harnessable source of energy.
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Re: Life: off topic continuation of " So linguistic time "

Postby daivid » Tue Apr 09, 2013 12:04 pm

Scribo wrote:I like the unknown, honestly if we were to find an alien civilisation with thousands of years of history and literature I'd jump ship in about ten seconds.


There are a vast number of planets in our galaxy so there is bound to be other planets with life.
But for most of earth's history bacteria has been the most complex form of life, hence even if many planets have life, the chances of complex life, let alone a civilization may be so rare that the nearest will be so far away that making any kind of contact will simply be impossible.

Finding life within our solar system (or not) would give us something to base a probability of finding life on a planet at all.

But in the entire history of our planet, only once has life developed beyond the level of bacteria to form complex cellular life. The leap from bacteria to a eukaryote (named after their κάρυον ie nucleus but that only scratches the surface of their greater complexity over bacteria) is huge and maybe so unlikely that only very few planets ever go beyond the bacteria-like phase. It would need us to discover not simply bacteria-like life but something as complex as an amoeba in our solar system for the likelihood of a planet with a civilisation within a reasonable distance to be a halfway serious possibility.
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Re: Life: off topic continuation of " So linguistic time "

Postby Paul Derouda » Tue Apr 09, 2013 9:03 pm

daivid wrote:
Scribo wrote:I like the unknown, honestly if we were to find an alien civilisation with thousands of years of history and literature I'd jump ship in about ten seconds.


There are a vast number of planets in our galaxy so there is bound to be other planets with life.
But for most of earth's history bacteria has been the most complex form of life, hence even if many planets have life, the chances of complex life, let alone a civilization may be so rare that the nearest will be so far away that making any kind of contact will simply be impossible.

Finding life within our solar system (or not) would give us something to base a probability of finding life on a planet at all.

Well, the paradox is: if civilizations are common, we would have already made contact. We haven't seen or heard anything, so they can't be too common. And even if civilizations were relatively common, interstellar travel is too difficult to be practical on a large scale, because otherwise aliens would be everywhere.

But in the entire history of our planet, only once has life developed beyond the level of bacteria to form complex cellular life. The leap from bacteria to a eukaryote (named after their κάρυον ie nucleus but that only scratches the surface of their greater complexity over bacteria) is huge and maybe so unlikely that only very few planets ever go beyond the bacteria-like phase. It would need us to discover not simply bacteria-like life but something as complex as an amoeba in our solar system for the likelihood of a planet with a civilisation within a reasonable distance to be a halfway serious possibility.

I think it's difficult to say which stage is the unlikely one. We really don't know if bacteria-like life forms are more common than civilizations... In my opinion the biggest leap is not from bacterium to eukaryot or multicellular lifeforms, but the moment when organic molecules capable of replicating themselves (probably RNA at this stage) acquired a lipid membrane, and thus became cellular. Because as far as I remember the idea was that before unicellular life there had to be "acellular" life, i.e. just organic molecules carrying genetic information "floating around"; when those molecules got a membrane, only then they could acquire metabolism etc.

But who says there wasn't other than RNA/DNA-based lifeforms on earth that were later displaced? And I think it's theoretically possible they still exist. First of all, they could be difficult to detect, because we're not looking for them. Then, they might occupy extreme habitats like bottoms of oceans, the south pole etc. And third, since they're so different ("incompatible") from the rest of us, they might be present in our living environment but not interact with us in any way - I mean at present, we mostly know about those microbes that are harmful to us, a bit less about those that are beneficial, and very little about the big majority that don't really affect us.

It's many years though since I read my rudiments of molecular biology...
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Re: Life: off topic continuation of " So linguistic time "

Postby daivid » Wed Apr 10, 2013 7:09 pm

Paul Derouda wrote:
daivid wrote:But in the entire history of our planet, only once has life developed beyond the level of bacteria to form complex cellular life. The leap from bacteria to a eukaryote (named after their κάρυον ie nucleus but that only scratches the surface of their greater complexity over bacteria) is huge and maybe so unlikely that only very few planets ever go beyond the bacteria-like phase. It would need us to discover not simply bacteria-like life but something as complex as an amoeba in our solar system for the likelihood of a planet with a civilisation within a reasonable distance to be a halfway serious possibility.

I think it's difficult to say which stage is the unlikely one. We really don't know if bacteria-like life forms are more common than civilizations... In my opinion the biggest leap is not from bacterium to eukaryot or multicellular lifeforms, but the moment when organic molecules capable of replicating themselves (probably RNA at this stage) acquired a lipid membrane, and thus became cellular. Because as far as I remember the idea was that before unicellular life there had to be "acellular" life, i.e. just organic molecules carrying genetic information "floating around"; when those molecules got a membrane, only then they could acquire metabolism etc.

I now understand why you are a lot more sceptical than I about finding life on other planets of this solar system than I. It's hard to see how life could be sustainable without membranes - but then again, as we have not seen such life in action, how can we be sure.
It is certainly true that bacteria and archaea may be primitive compared to eukaryotes but they are also clearly the product a lot of evolution and are sophisticated compared with what must have gone before.
But the very fact we have two bacteria like forms on our planet (ie bacteria themselves and archaea) suggests that that was not where the most significant bottle neck lay - and it is their cell walls that one of the key differences lie.

Eukaryotes are one-offs and the fact they seem to have arisen from a fusion of an archaea and a bacteria suggests that arose from something very unlikely - certainly not text book small changes channelled by natural selection.

By contrast is far harder to even guess how hard it was to produce archaea and bacteria as the forms of life they grew our of are (probably??) now extinct.

But your point makes me aware that I don't know far too little about lipid membranes and would worth while for me to do at least a reading in this area.


But who says there wasn't other than RNA/DNA-based lifeforms on earth that were later displaced? And I think it's theoretically possible they still exist. First of all, they could be difficult to detect, because we're not looking for them. Then, they might occupy extreme habitats like bottoms of oceans, the south pole etc. And third, since they're so different ("incompatible") from the rest of us, they might be present in our living environment but not interact with us in any way - I mean at present, we mostly know about those microbes that are harmful to us, a bit less about those that are beneficial, and very little about the big majority that don't really affect us.

It's many years though since I read my rudiments of molecular biology...


I do remember seeing a TV program that showed a woman looking for life in arsenic contaminated areas. No one looks for life there because arsenic destroys DNA and so life there is impossible. Unless it is non DNA life you are looking for.
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Re: Life: off topic continuation of " So linguistic time "

Postby Paul Derouda » Thu Apr 11, 2013 9:48 am

daivid wrote:I now understand why you are a lot more sceptical than I about finding life on other planets of this solar system than I. It's hard to see how life could be sustainable without membranes - but then again, as we have not seen such life in action, how can we be sure.
It is certainly true that bacteria and archaea may be primitive compared to eukaryotes but they are also clearly the product a lot of evolution and are sophisticated compared with what must have gone before.
But the very fact we have two bacteria like forms on our planet (ie bacteria themselves and archaea) suggests that that was not where the most significant bottle neck lay - and it is their cell walls that one of the key differences lie.

I must say I'm not an expert on molecular biology, I just know what I remember from what learnt at medical school about 12 years ago. So take this with a grain of salt... But yes, I guess the bottle neck was probably before bacteria and archae separated. But like you say, we'd really need to have more examples to know for sure... Keep in mind though there's a big difference between cell membrane and cell wall - a cell membrane is a vital, thin lipid layer all cells have, while a cell wall is a sort of extra support and is (I'm pretty sure) a relatively late development only found in some types of cell (some bacteria and plant cells at least).
Eukaryotes are one-offs and the fact they seem to have arisen from a fusion of an archaea and a bacteria suggests that arose from something very unlikely - certainly not text book small changes channelled by natural selection.

I have a faint recollection that the particularities of bacteria - like the fact they have little non-coding DNA, unlike eukaryotes - is rather an adaption than just a sign of their primitivity. But I'm not sure that the apparent similarities between eukaryotes and archae relative to bacteria is necessarily due to the eukariotic genome being derived from archae (though of course all known life here has ultimately a common origin), it could be just that they have been more "conservative" in some respects than bacteria. Also, the symbiosis of eukaryotes and the bacteria that would then become mitocondria didn't happen just once - chloroplasts also probably have a bacterial origin.

By contrast is far harder to even guess how hard it was to produce archaea and bacteria as the forms of life they grew our of are (probably??) now extinct.

No, they're not extinct - they have a lot of descendants, at least archae and bacteria... ;) In billions of years there's bound to be change.

But your point makes me aware that I don't know far too little about lipid membranes and would worth while for me to do at least a reading in this area.

The book I was reading long ago was Alberts et al.'s Molecular Biology of the the Cell. It was the 3rd edition, now the book is at its fifth, apparently completely rewritten since then. The one I read was very good at least. It's a huge volume though, I never read it entirely, and there must be more concise books. The parts I preferred where short digressions where the authors speculated what this or that fact might indicate as to the origin of life...
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Re: Life: off topic continuation of " So linguistic time "

Postby Paul Derouda » Wed May 29, 2013 6:11 pm

Ran into this.

"An extrapolation of the genetic complexity of organisms to earlier times suggests that life began before the Earth was formed."

The idea is fascinating. I don't have the competence to evaluate how good the argumentation is.
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Re: Life: off topic continuation of " So linguistic time "

Postby Scribo » Wed May 29, 2013 7:21 pm

Confession: Had I the skills I'd take this stuff and write an excellent novel and become loaded.
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Re: Life: off topic continuation of " So linguistic time "

Postby daivid » Fri May 31, 2013 8:40 pm

Paul Derouda wrote:Ran into this.

"An extrapolation of the genetic complexity of organisms to earlier times suggests that life began before the Earth was formed."

The idea is fascinating. I don't have the competence to evaluate how good the argumentation is.


Thanks for that. The bit that I found most interesting was when he discussed the possibility that life originating on the surface of oil bubbles. However, I have read almost nothing on the origin of life so I'm definitely in the "not having the competence to evaluate category" for that bit. Nonetheless, they does go into some detail and what they seems strongly based.

Their basic contention, however, is that the rate of increasing complexity has grown and will continue to grow exponentially. They don't really justify that in the that paper but there is a reff to http://www.biology-direct.com/content/1/1/17 where Sharov does attempt this. It seems to me that he does so by being somewhat selective. He excludes plants on the grounds that their increase in complexity has been slow and he wanted to concentrate on the "best performer". It does seem to me in doing so he has selected just those examples that suit his thesis.

But it is the way he treats the prokaryotes that I have the biggest problem. His starting point is to take the most primitive bacteria today and assume that is what the first bacteria were like. Then comparing that with most complex bacteria we see today he takes the life that is known to exist 3.5 billion year ago and gets a rather low figure for increasing complexity.

There several problems I have with that but the key one is that he assumes that the growth in complexity has been constant. He suggests that the reason that archea and bacteria develop slowly is that their error checking is too primitive. The explanation that I favor is that the because they don't have mitochondria there is an upper limit to the amount of energy they can metabolize. For the largest bacteria and archea the energy needed to produce the DNA needed is a big overhead when they divide. Hence no bacteria is going to get any more complex than what we see today because if they did they would be out bred by bacteria with more streamlined genomes. I suspect that when when prokaryotes first appeared they very quickly developed complex forms like the most complex bacteria we see today and then got stuck.

On a deeper level I am suspicious of anyone trying to see natural selection as a method of producing "progress" where as really it simply favors survivors and if more primitive ecological niches are available that is what natural selection will nudge organisms to fill.

His argument that DNA forms could be transported across space is seems spot on. But just because life could have arrived on earth from elsewhere doesn't mean it did.


There is, however, a more emotional reason why I hope he is wrong. When I look at Europa and see those red-brown stains I can't help myself feeling (despite a total lack of evidence) that I am looking at alien life. Were we to get there and find that it was just more DNA-life there would be a part me that would be sort of disappointed. :(
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Re: Life: off topic continuation of " So linguistic time "

Postby Paul Derouda » Sat Jun 08, 2013 9:03 pm

daivid wrote:But it is the way he treats the prokaryotes that I have the biggest problem. His starting point is to take the most primitive bacteria today and assume that is what the first bacteria were like. Then comparing that with most complex bacteria we see today he takes the life that is known to exist 3.5 billion year ago and gets a rather low figure for increasing complexity.

If indeed he's assuming that the prokaryotes 3.5 billion years ago were like the most primitive bacteria today, that might be a problem. Anyway, the article treats many technical questions I'm not familiar with at all. But I was glad to find it seemed to confirm my ideas that 1) life at the prokaryot level is "very unlikely", that the step from zero to prokaryot is bigger than the one from prokaryot to eukaryot - though it never occured to me that someone could argue that life must be older than the earth, and that 2) life could have started from lipid membranes/oil bubbles, though I wasn't aware of the (very plausible theory) that the lipid membranes themselves could be the carriers of (rather simple) genetic information.

I'm not saying I fully accept this argument just like this but I must confess this has had a profound impact on how I think about the origin of life, more than anything since I read my basics of molecular biology over ten years ago. If you find a strong counterargument, I'd like to know...
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