Was The Transition From Unicellular To Multicellular

[Gold Barz]

Bound to happen?, was it inevitable since multicellular organisms has a lot more advantages than unicellular organisms.

 

[Gold Barz]

Also...Alien Cells To Alien Civilizations

Do you think we are alone or they are out there? (not alien organisms but going farther than that intelligent alien species)

Personally, I think there are millions of alien civilizations out there at anyone time, the building blocks of life are found in abundance in deep space, plus the c0mplexity of organisms has only two directions it will either stay the same or it will increase in c0mplexity but it can never decrease in c0mplexity, so over time there eventually will be a growth in maximum c0mplexity in atleast one ogranism. The fittest will survive while the weak gets "weeded out" over time, the more "fitter" an organism is the more complex it has to be (they go hand in hand) and when there are a lot of "fit" organisms there will be an arms race and that will lead to an explosion of c0mplexity, when the more simpler niches are filled that will make way for more complex niches to be filled. Let's say organism one can survive in environments A and B but organism two can survive in environments A,B and C...over time who do you think will get "weeded out" and who do you think will thrive.

Survival of the fittest, the more adaptive specie will survive and thrive.

And once there are creatures like the animals have emerged, then there is a great chance that atleast one of those animals will evolve into an intelligent bunch.

 

[JamesU]

do you put the "0" in complex or only complexity?

 

[Gold Barz]

Complexity..it was because on the original message board I posted this in the word complexity was ***'d out for some reason.

 

[arildno]

Bound to happen?, was it inevitable since multicellular organisms has a lot more advantages than unicellular organisms.

Oh ,do they?
That's new to me.
Please note that the overwhelming part of the Earth's biomass is in the form of unicellular organisms.

Multicellular organisms are just exotic aberrations to the norm.

 

[Gold Barz]

Or you could get a lot more done if you work together, that's a big advantage, its not just "exotic abberations".

 

[quasi426]

Bound to happen?, was it inevitable since multicellular organisms has a lot more advantages than unicellular organisms.

To this I query: If multicellular organisms had such an advantage over unicellular organisms then why have they not gone extinct (unicellular life)? Life has many solutions. There are many ways to deal with the physical world organims are placed against. Different organims find different solutions to this problem. And how do they know if the solution is correct? Well natural selection will guide this evolving process to a path that works. All the organisms that are around today have found a way to survive and procreate. So multicellular organisms as well as intelligence is not an essential ingredient of life and therefore not inevitable.

 

[arildno]

Or you could get a lot more done if you work together, that's a big advantage, its not just "exotic abberations".

A lot more done?
What ARE you talking about?

Instead of indulging in silly and misplaced value judgments, you might do better to actually learn to OBSERVE and UNDERSTAND things around you.

 

[Moonbear]

There are a number of misconceptions about evolution apparent in your post, so I'm going break it down part by part to explain where the misunderstandings are.

plus the c0mplexity of organisms has only two directions it will either stay the same or it will increase in c0mplexity but it can never decrease in c0mplexity, so over time there eventually will be a growth in maximum c0mplexity in atleast one ogranism.

That's not true. Certain parasites, like tapeworms, are an excellent example of organisms that have become less complex than ancestral species. Because they can extract nutrients directly from their hosts, they don't need complex digestive systems.

The fittest will survive while the weak gets "weeded out" over time, the more "fitter" an organism is the more complex it has to be (they go hand in hand) and when there are a lot of "fit" organisms there will be an arms race and that will lead to an explosion of c0mplexity, when the more simpler niches are filled that will make way for more complex niches to be filled.

Natural selection is very specific to the environment it is occurring in. It also doesn't necessarily require that one variant of a species be "weak." It just means that another variant is better suited to the environment, so the proportion of the species exhibiting that trait, over time, increases (Hardy-Weinberg Principle). The other variant does not necessarily disappear entirely, which is good if the environment changes and that variant is more suited for the changed environment. If a variant is sufficiently detrimental in a particular environment, such that no individuals exhibiting it can survive to reproduce, and the trait is lost, this is a loss of variation. It could even be a loss of complexity. Niches are not more or less complex either. Niches are just environments.

Let's say organism one can survive in environments A and B but organism two can survive in environments A,B and C...over time who do you think will get "weeded out" and who do you think will thrive.

That's overly simplistic. Both species may coexist in the same environment. Or, the organism that can only survive in environment A&B (Organism 1) may be thriving there, while the other organism (Organism 2) is competed out of that environment and forced into only environment C. Now, another species may come along and start destroying environment C, say a simple fungus that kills the plants Organism 2 needs to eat.

Survival of the fittest, the more adaptive specie will survive and thrive.

Keep in mind, adaptability is dependent on pre-existing genetic variability, and a lot of chance that among the variants of that species, at least one exists that can survive in a new environment. And sometimes living in a highly selective environment for a long period of time (thriving) leads to loss of some of that variation due to strong selection for a few traits. In the end, this thriving species may be the least able to adapt to an environmental change because it has become too specialized. So, thriving and adaptability do not necessarily need to go together as long as the environment is present where the specialized species can survive.

And once there are creatures like the animals have emerged, then there is a great chance that atleast one of those animals will evolve into an intelligent bunch.

Maybe, maybe not. There's no predetermined direction for evolution to occur, so this is not a guaranteed outcome, and not necessarily even highly probable. You may end up with nothing more than a bunch of animals that never even develop a true brain, such as worms.

 

[Moonbear]

Or you could get a lot more done if you work together, that's a big advantage, its not just "exotic abberations".

That would be an advantage to colonial organisms (colonies of single-celled organisms), but not relevant to multicellular organisms. Multicellular organisms, and in general, more complex organisms, require increased energy to maintain their function. This is a disadvantage of multicellular organisms relative to single-celled organisms.

 

[arildno]

Great posts, Moonbear!

As I see it, it is the abundance of bacteria and other small-scale life which opens up new niches for new forms of life which have the bacteria themselves as their primary food source.

Thus, we ought to regard "higher" organisms as ourselves as secondary life forms, and not as having reached the pinnacle of evolution or something.
Our existence is largely irrelevant for the microbial world (other than being an alternative food source for them); in contrast, multicellular life would practically collapse overnight if we removed the bacteria from the earth..

 

[Gold Barz]

Well, wow I was very misinformed about evolution then. Would you guys say then intelligence is a rare occurance? and if Earth was restarted ten times it would happen only once?

"Multicellular organisms, and in general, more complex organisms, require increased energy to maintain their function. This is a disadvantage of multicellular organisms relative to single-celled organisms." - Then, why did the transition to unicellular to multicellular happen? I am just asking because it seems like multicellular does not have a lot of advantages over unicellular now.

"Maybe, maybe not. There's no predetermined direction for evolution to occur, so this is not a guaranteed outcome, and not necessarily even highly probable. You may end up with nothing more than a bunch of animals that never even develop a true brain, such as worms." - Even with environmental pressures?

 

[Moonbear]

Well, wow I was very misinformed about evolution then.

No problem. It's a common mistake. It's probably a topic textbooks should spend a little more time emphasizing in the chapters on evolution and natural selection since it's such a common misunderstanding. But, there's only so much you can include in a single textbook.

Would you guys say then intelligence is a rare occurance? and if Earth was restarted ten times it would happen only once?

It's hard to predict an answer to that question. Certainly among all the species that currently exist on our planet (since we can't assess intelligence directly in extinct species), it is a rare occurrence (even if you use a liberal definition of intelligence, it's pretty much limited to vertebrates and cephalopods, and possibly only in humans and maybe dolphins and the other primate species if you use a more conservative definition).

"Multicellular organisms, and in general, more complex organisms, require increased energy to maintain their function. This is a disadvantage of multicellular organisms relative to single-celled organisms." - Then, why did the transition to unicellular to multicellular happen? I am just asking because it seems like multicellular does not have a lot of advantages over unicellular now.


"Maybe, maybe not. There's no predetermined direction for evolution to occur, so this is not a guaranteed outcome, and not necessarily even highly probable. You may end up with nothing more than a bunch of animals that never even develop a true brain, such as worms." - Even with environmental pressures?

I'm not exactly sure what you're asking here. Do you mean if the environmental pressures/changes were exactly the same? If so, here's the rub. There's still a good deal of chance involved. Most mutations that contribute to variability and speciation are "errors" in chromosome replication during cell division in the gametes (or damage caused by environmental factors). While there are areas of chromosomes that are more susceptible to mutations (probably something Monique can talk more about than I can), any part could have a mutation during cell division.
So even under identical environmental conditions, completely different mutations or none at all could occur.

In anticipation of the next question or where the above might start getting confusing, keep in mind that natural selection and evolution are not synonymous. Natural selection is how environmental factors influence the survival of individuals within a species that have certain traits and affects the proportion of individual in a population that have that trait. These variations in traits must already exist for natural selection to be a factor. Evolution is the change of the species over time, the overall accumulation or loss of traits (not just selection from among previous variations of those traits), until they have become sufficiently different to be unable to interbreed with the ancestral species, thus, at a population level, a new species is formed. Natural selection helps this process along by eliminating unfavorable traits, but it's not the "cause" of evolution, which is sometimes another misconception people hold.

 

[arildno]

GoldBarz:
Why do you keep talking about a "transition" from unicellular life to multicellular life?
There hasn't been any such "transition", since the vast majority of life is still in a unicellular form.

 

[matthyaouw]

"Multicellular organisms, and in general, more complex organisms, require increased energy to maintain their function. This is a disadvantage of multicellular organisms relative to single-celled organisms." - Then, why did the transition to unicellular to multicellular happen? I am just asking because it seems like multicellular does not have a lot of advantages over unicellular now.

In some circumstances perhaps they do have advantages, hence why they are able to survive, but in others, simple organisms can dominate. Take for example your skin and intestines- they themselves are ecological niches, filled primarily with bacteria living in symbiosis with humans. You would be hard pressed to find a complex organism more suited to either environment, and that is just one example out of many. Simple organisms can generally withstand a much wider range of ph, temperature etc than complex ones, giving them many niches where they have the advantage. I don't honestly think its posible to effectively compare the advantages and disadvantages of such broad groups with no reference to specific conditions.

"Maybe, maybe not. There's no predetermined direction for evolution to occur, so this is not a guaranteed outcome, and not necessarily even highly probable. You may end up with nothing more than a bunch of animals that never even develop a true brain, such as worms." - Even with environmental pressures?

You still seem to be under the misconception that when faced with any kind of problem, complexity is the way to go. This is not the case. I think its fairly safe to say that all species are under constant environmental pressures of some degree, and yet, as has already been said, the most numerous organisms on the planet are simple and unicellular still.

 

[Gold Barz]

GoldBarz:
Why do you keep talking about a "transition" from unicellular life to multicellular life?
There hasn't been any such "transition", since the vast majority of life is still in a unicellular form.

You knew what I meant, sorry.

Wow, I got roasted on this thread lol. I am willing to learn though.

But I think I made a mistake stating something, I did not mean that the average organism will increase in complexity over time I meant that the maximum complexity an organism could have could in fact increase.

I think the best definition of evolutionary progress by means of natural selection that I can think of is a growth in the overall complexity of organisms that allows them to exercise increasing control over their environment.

Anyways, you guys should read the link below, its a good read.

http://pespmc1.vub.ac.be/Papers/ComplexityGrowth.html

 

[matthyaouw]

I think the best definition of evolutionary progress by means of natural selection that I can think of is a growth in the overall complexity of organisms that allows them to exercise increasing control over their environment.

No. Evolution is non-directional process. It is still evolution if the species simplify over time. Control over environment could be a result of evolution, but it is into way integral to its definition.

 

[Gold Barz]

Did you read the link above

 

[arildno]

I am willing to learn though.

In the end, that's all that matters.

 

[Gold Barz]

So do you guys think intelligence is a one in a million type thing in the universe and that we are likely alone in the galaxy?

 

[matthyaouw]

At the moment I'm reading a book called Rare Earth by Ward & Brownlee, and they argue just that. They say that simple bacterial life may be widespread in the universe, but it was a very specific and rare set of conditions that allowed the rise of complex forms such as animals and plants. I can't go into too much detail as I've not got too far into it yet.

 

[Gold Barz]

What is the main reason you guys don't think complexity doesn't increase over time in evolution?

Is it because the most simple type of life, bacteria, extremely dominates Earth and its biomass?

 

[arildno]

Goldbarz:
1) There is quite a difference between
a) saying that there is an inevitable trend towards increasing "complexity",
and
b) merely observing that, yes,in the course of time here at Earth several fairly complex organisms have evolved.

If you look back at your previous reply, you seemed to indicate 1a), to which I objected.

2) As for probability of existence of other intelligences in the galaxy, we really don't have sufficient data to estimate that probability in any scientific manner.

On a personal note, I'm fully convinced that there exist many intelligences in the galaxy; we have as little justification in asserting that evolution on Earth has been a freak occurence as in saying that all evolution must follow the Earth pattern.

 

[Gold Barz]

Then we have just been misunderstanding each other because I agree with your "personal note" statement and that now I have learned that increasing complexity is not inevitable but I also don't think its rare too.

You and Moonbear have been a huge help.

Thanks a lot guys.

 

[arildno]

Moonbear certainly clarified a lot for me as well.
Although I was somewhat familiar with the topics she broached in beforehand, it is always rewarding to read a clear, succinct exposition of them that only a professional like herself can give.

 

[Moonbear]

Moonbear certainly clarified a lot for me as well.
Although I was somewhat familiar with the topics she broached in beforehand, it is always rewarding to read a clear, succinct exposition of them that only a professional like herself can give.

And I'm always worried that I have a tendency to ramble and might just confuse everyone more.

 

[Gold Barz]

Moonbear, in your personal opinion, do you think intelligence has risen more than once in our galaxy...for me I would think so, maybe and this is just an off the wall guesstimate, thirty to a hundred alien civilizations existing at anyone time, cause there is about 100 billion stars in the galaxy, I think fifty "feels" more accurate.

Also Moonbear, if the human race suddenly went extinct, which species do you think would have the best chance in taking over our spot as the more intelligent species on planet Earth.

And for anyone reading this, do you think other planets that is not exactly similar to Earth could have something totally different evolve on that planet, maybe intelligence can rise quicker on a different type of planet, but it obviously have to be terrestrial and have water.

 

[Moonbear]

Moonbear, in your personal opinion, do you think intelligence has risen more than once in our galaxy...for me I would think so, maybe and this is just an off the wall guesstimate, thirty to a hundred alien civilizations existing at anyone time, cause there is about 100 billion stars in the galaxy, I think fifty "feels" more accurate.

Honestly, this isn't something I've formed an opinion on. In our galaxy, I'd suspect pretty unlikely. In the universe, possible.

Also Moonbear, if the human race suddenly went extinct, which species do you think would have the best chance in taking over our spot as the more intelligent species on planet Earth.

The next most intelligent species. But then that's just a relative measure anyway, isn't it? It doesn't mean I think another species is going to suddenly become more intelligent because we aren't around, just that the second most intelligent would naturally be the most intelligent if the most intelligent was wiped out (and how do we know for certain we are the most intelligent? We think we are, but maybe those dolphin squeals are really them laughing at us for being so stupid ...no reason for picking dolphins specifically here other than a lot of people argue they are intelligent).

And for anyone reading this, do you think other planets that is not exactly similar to Earth could have something totally different evolve on that planet, maybe intelligence can rise quicker on a different type of planet, but it obviously have to be terrestrial and have water.

Still in the realm of complete speculation, anything could happen. There could be intelligent life somewhere else, there could be no life anywhere else, there could be life that is so completely different from life on Earth that we wouldn't even recognize it as life if we saw it. Until and unless we actually observe life from another planet/part of the universe, we have no way to know or even to make a reasonable guess at what features it might have. Of course, if you visit the Skepticism and Debunking forum, you'll know there are plenty of people who claim to have observed, even been contacted by, intelligent life from other planets, but so far, the accountings aren't terribly credible.

 

[Gold Barz]

Wow...just us in the whole galaxy? that's like 100-200 billion stars but of course there's a certain part that is in the habitable zone. In my opinion intelligence is not likely but due to the amount of stars and planets there are, there still should be many many alien civilizations. So your a Rare Earth supporter Moonbear?

Arildno, did you get my PM?

 

[Moonbear]

Wow...just us in the whole galaxy? that's like 100-200 billion stars

Do you expect anything to be able to live on a star?! I suspect any life would have a lot better chance someplace a tad bit less "toasty."

 

[Gold Barz]

Most stars have debris around them

 

[Nereid]

And I'm always worried that I have a tendency to ramble and might just confuse everyone more.

Well, dear MB, how can we straighten out your misconceptions, hmm?

Perhaps I'll create a poll, something like "what % of Moonbear's posts here in PF do you consider to be rambly and confusing a) 2% b) 1% c) 0.1% d) Moonbear does not post rambly and confusing posts Nereid, you of all people should recognise the ridiculousness of even asking such a stupid question!"


:!)

 

[Nereid]

Did you read the link above

It's quite interesting, isn't it?

I particularly liked this part: "It turns out that complexity is itself a complex concept: difficult to define and to model, and easy to misinterpret. To a certain extent, complexity is in the eye of the beholder: what is complex for one observer, may be simple for another one.[/color]" At the very least this makes your first question:

What is the main reason you guys don't think complexity doesn't increase over time in evolution?

impossible to answer - I could give you a reason, only to find that we were talking past each other (your idea of complexity and mine differ, possibly in an obvious way; more likely in subtle ways that would require dozens of pages of exchanges to bring to light).

Moonbear, in your personal opinion, do you think intelligence has risen more than once in our galaxy...for me I would think so, maybe and this is just an off the wall guesstimate, thirty to a hundred alien civilizations existing at anyone time, cause there is about 100 billion stars in the galaxy, I think fifty "feels" more accurate.

Well, I'm not Moonbear, but if I may say something?

First, we have moved way, way beyond Biology, and are barely hanging onto any kind of science ... while this topic is fascinating (one of my favourites), I don't think this is the place to discuss it.

Second, how to you assess 'intelligence'? 'civilizations'?

One approach is 'just like us'; this is (more or less) the approach Ward and Browlee took (and, really, the only one that could claim any scientific component; after all, we're trying to generalise from a sample of one!).

And for anyone reading this, do you think other planets that is not exactly similar to Earth could have something totally different evolve on that planet, maybe intelligence can rise quicker on a different type of planet, but it obviously have to be terrestrial and have water.

And this is, I'm sure you'll agree, pure speculation!

 

[juvenal]

http://www.newyorker.com/fact/content/articles/050530fa_fact

This is a nice article.

Although proponents of I.D. routinely inflate the significance of minor squabbles among evolutionary biologists (did the peppered moth evolve dark color as a defense against birds or for other reasons?), they seldom acknowledge their own, often major differences of opinion.

I find that this applies to a majority of cranks.

 

[Gold Barz]

So its likely that a planet with life would have just some "dumb" animals?

 

[Nereid]

So its likely that a planet with life would have just some "dumb" animals?

The Ward and Browlee thesis is that 'a planet with life' would likely have little more than unicellular organisms, and maybe not more than just bacteria (and archaea) - we're talking of carbon-based life here, of the kind we are familiar with; I am unaware that there's been any significant science done on what other kinds of life there might be in the universe.

However, since a) we have only studied 'life' on Earth, b) we've only studied one other body enough to rule out 'life' (the Moon), and c) we know next to nothing about the conditions conducive to life (and how they change) on any planet outside our solar system, any statements about what life would be like on 'a planet' must be almost entirely speculative.

 

[Gold Barz]

Well, we know that animals did evolve on this planet, there are also ALOT of different kinds of them...

What Peter Ward said:

"It has always been assumed that attaining the evolutionary grade we call animals would be the final and decisive step. Once we are at this level of evolution, a long and continuous progression toward intelligence should occur. However, recent research shows that while attaining the stage of animal life is one thing, maintaining that level is quite another. The geologic record has shown that once evolved, complex life is subject to an unending succession of planetary disasters, creating what are known as mass extinction events. These rare but devastating events can reset the evolutionary timetable and destroy complex life while sparing simpler life forms. Such discoveries suggest that the conditions allowing the rise and existence of complex life are far more rigorous than are those for life's formation. On some planets, then, life might arise and animals eventually evolve - only to be soon destroyed by a global catastrophe."

So it seems like evolution of animals is not really that difficult to attain but its harder to maintain...also I think these "rare and devastating events" only sped up our ancestors evolution to intelligence, maybe it might do the same for another species on another planet?

http://www.astrobio.net/news/article239.html

 

[Gold Barz]

Also David Grinspoon makes a great point:

"David Grinspoon: I think it is a mistake to look at the many specific peculiarities of Earth's biosphere, and how unlikely such a combination of characteristics seems, and to then conclude that complex life is rare. This argument can only be used to justify the conclusion that planets exactly like Earth, with life exactly like Earth-life, are rare.

My cat "Wookie" survived life as a near-starving alley cat and wound up as a beloved house cat through an unlikely series of biographical accidents, which I won't take up space describing but, trust me, given all of the incredible things that had to happen in just the right way, it is much more likely that there would be no Wookie than Wookie. From this I do not conclude that there are no other cats (The Rare Cat Hypothesis), only that there are no other cats exactly like Wookie.

Life has evolved together with the Earth. Life is opportunistic. The biosphere has taken advantage of the myriad strange idiosyncrasies that our planet has to offer. Not only that, life has created many of Earth's weird qualities. So it is easy to look at our biosphere, and the way it so cleverly exploits Earth's peculiar features, and conclude that this is the best of all possible worlds; that only on such a world could complex life evolve. My bet is that many other worlds, with their own peculiar characteristics and histories, co-evolve their own biospheres. The complex creatures on those worlds, upon first developing intelligence and science, would observe how incredibly well adapted life is to the many unique features of their home world. They might naively assume that these qualities, very different from Earth's, are the only ones that can breed complexity."

http://www.astrobio.net/news/article239.html

 

[Moonbear]

Also David Grinspoon makes a great point:

"David Grinspoon: I think it is a mistake to look at the many specific peculiarities of Earth's biosphere, and how unlikely such a combination of characteristics seems, and to then conclude that complex life is rare.

The converse would also be true. It would be a mistake to look at the evolution of so many diverse forms of life on this planet and conclude it would also be common elsewhere.

As has already been stated by others here, we have a sample set of ONE. One intelligent species on one planet in one galaxy. Based on a sample of one, you cannot predict ANYTHING about likelihood of something happening again somewhere else. There are no trends we can observe, no patterns, no common sets of conditions that are required.

I think you need to find more credible sources than from people who would try to draw predictions and conclusions about the rest of the universe from their observations of a single planet. One can do no more than hand wave and wildly guess about life in the rest of the universe. There is nothing scientific about that. Likewise, we cannot deny the possibility there is life elsewhere in the universe, but until we observe it, we can't make any predictions whatsoever about it. Our planet could be an aberration for having life, or our galaxy could be an aberration for having so many planets without life.

 

[arildno]

I would like to chime in with Moonbear here:
We lack the evidence as to whether the formation of life is a commonly occurring process, or something extremely rare. We can't make statistics out of a single datum!

My subjective opinion is that there are lots of life in the galaxy, but that's a subjective opinion I hold. It is a belief I've got, but I don't have any reasons for this view that I regard as rock-solid and irrefutable.

 

[Gold Barz]

The converse would also be true. It would be a mistake to look at the evolution of so many diverse forms of life on this planet and conclude it would also be common elsewhere.

As has already been stated by others here, we have a sample set of ONE. One intelligent species on one planet in one galaxy. Based on a sample of one, you cannot predict ANYTHING about likelihood of something happening again somewhere else. There are no trends we can observe, no patterns, no common sets of conditions that are required.

I think you need to find more credible sources than from people who would try to draw predictions and conclusions about the rest of the universe from their observations of a single planet. One can do no more than hand wave and wildly guess about life in the rest of the universe. There is nothing scientific about that. Likewise, we cannot deny the possibility there is life elsewhere in the universe, but until we observe it, we can't make any predictions whatsoever about it. Our planet could be an aberration for having life, or our galaxy could be an aberration for having so many planets without life.

How do you know that intelligence only popped up once in the Milky Way though.

 

[Moonbear]

How do you know that intelligence only popped up once in the Milky Way though.

You're missing the point. We don't know anything about life anywhere other than on Earth (it would be BIG news if someone discovered life somewhere else, just like it was when they thought they had discovered some fossils of microorganisms on Mars). That is why we cannot predict anything about any place else in the universe.

 

[Gold Barz]

Okay, so you can't say its a definate yes or no or how unlikely or likely it is then, but is it okay for me to think that there are other intelligent life on other planets in the galaxy (like arildno), would I be just fooling myself or is it reasonable?

"it would be BIG news if someone discovered life somewhere else, just like it was when they thought they had discovered some fossils of microorganisms on Mars" - When did this happen?

 

[selfAdjoint]

Okay, so you can't say its a definate yes or no or how unlikely or likely it is then, but is it okay for me to think that there are other intelligent life on other planets in the galaxy (like arildno), would I be just fooling myself or is it reasonable?

You could look on it as entertainment, but it has nothing to do with science. Traditionally, "reasonable" includes respect for Occam's Razor, that you don't indulge yourself in believing hypotheses for which there is no evidence.

"it would be BIG news if someone discovered life somewhere else, just like it was when they thought they had discovered some fossils of microorganisms on Mars" - When did this happen?

There was a little fuss a couple of years ago. It didn't pan out.

 

[arildno]

Since the evidence we've actually got is that there exists at least one planet teeming with life, it is not more reasonable to say that this the only planet in the galaxy which exhibits life than to say there might well be others exhibiting life.

 

[Gold Barz]

I agree with arildno, I don't think life or intelligence for that matter is that rare.

Cuase I hate believing in false stuff selfAdjoint, so if I believe in other intelligent aliens in our galaxy, would i be believing in false stuff?

 

[selfAdjoint]

The unknowable is neither true nor false, neither untrue nor unfalse. It's just not knowable in any way. To believe it is not so much wrong as silly. Likewise to BELIEVE there are no intellegent life forms elsewhere in the galaxy, in the absence of any evidence, is also silly.

 

[arildno]

Silly is such a strong word; feel free to believe whatever you like, GoldBarz, as long as you are clear about that what evidence we've got is woefully insufficient to extrapolate from in a scientific manner.

 

[Gold Barz]

Yes...because we have no evidence at all.

So selfAdjoint, then I should not believe in alien civilizations in this galaxy nor I should believe that there arent any alien civilizations in this galaxy? So basically keep an open mind to both possibilites, although I have to admit I find it pretty hard to stomach the possibility of just us being the only civilization in the galaxy.

Another interesting question here is would the essentials we have here on Earth apply to alien civilizations too like:

Food; hunting and gathering
Shelter; building "homes" and other structures

Imagine what alien entertainment would be like, like alien sports or some kind of competition?

 

[Nereid]

Actually, Gold_Barz, we already have some pretty good (say, 99% or even closer to 100%) data ... of a negative kind:
- there is no intelligent life exactly like us Homo sap. (civilizations, late 20th century technology and all) on any planet or moon or asteroid in our solar system (except Earth); why? because we have not found anything that looks like a 'I Love Lucy' TV broadcast or mobile/cellphone traffic (among other things)
- ditto, on planets around stars within ~25 lightyears of us (ditto)
- there are no ecosystems (assemblages of 'life') like the major surface (and near surface) ones on Earth on any moon, asteroid or other planet in our solar system; why? because no other solar system body has 'the right' atmosphere, reflection bands showing chlorophyll, etc

You can refine these statements to varying degrees - and that can be quite good fun - but it doesn't get you very far.

Now here's something you might like to chew on: when we get to do some decent 'fossil hunting' on Mars, will be find that life once existed there? Will the 'fossils' likely be chemical traces (such as those we use to conclude that there was life on Earth at the time of the oldest currently preserved rocks)? microfossils (undifferentiated cells, differentiated cells)? trace fossils (e.g. 'worm burrows')? primative eukaryote-like fossils? ...

If we do find that there was once 'simple life' (similar to Earthly bacteria and archaea) on Mars, would this be a huge surprise to astrobiologists? If we failed to find any such, would that be a huge surprise? In either case, why (not)?

Remember, astrobiologists think they are scientists ... so whatever expectations they have re 'ancient life' on Mars you may assume are pretty firmly based in good science.