Life in Universe: Is Intelligent Life Inevitable?

[Chronos]

I have way too much free time since I retired.

 

[Whovian]

I also don't see why there can't be forms of life very different from ours that have nothing to do with atoms. In fact since atoms are quite rare in this Universe I would think non-atomic life would be much more common.

Then what would they be formed out of? Fundamental bosons have almost no capability to combine into bodies. Perhaps dark matter life, but that would have no basis yet other than "there's this dark matter stuff and we don't know exactly what it is so life could be made out of it."

I have way too much free time since I retired.

Studying history? Yep, you do.

 

[Ryan_m_b]

I don't understand this, because it seems like you are just making a whole series of assertions that you think are obvious, but what you say is not at all obvious to me, and there is nothing to back any of them up. Could you maybe elaborate on what you think the unlikely sequence of events and blind luck was that led to the development of Homo sapiens, and why it is, in your estimation, so improbable, even given nearly identical conditions on some other planet?

Most mutations are inherently random, natural selection then works in a non-random way on the products of these mutations. Because of this if you start out with two identical populations in two identical environments or hypothetically rewound Earth back to a former state it is extremely unlikely that you will get the same evolutionary processes.

 

[mfb]

Depending on how you interpret the timeline, life began relatively quickly (only a few 100My) after the crust cooled enough to allow it. By comparison, the the step from unicellular life to multi-cellular life took as much as a Gy.

IIRC this is because it took billions of years to do alter the environment (e.g free oxygen) to a level where more complex life was possible. Not that I disagree with anything else you say, it's certainly a possibility.

Both steps were not the result of single, unlikely events, therefore the involved time-scale cannot be used to compare their probability.
There is nice toy model to show this: Assume that the evolution from "cellular life in some way" to "multicellular life" needs 10^3 major evolution steps in some way. Assume that each step happens randomly at a single time, with an expected time of 1 million years. This is horribly wrong, of course, as there are multiple ways to multicellular life - but it shows the general idea. Using this model, the expected time for the evolution is 1Gy. However, the probability for the process taking less than 0.9Gy or more than 1.1Gy is close to 0. Therefore, you would expect this process on all planets with the same initial conditions and enough time.

1. The Drake equation is interesting in that it describes parameters for determining the probability of other life, but it is useless whether or not the parameters are well defined. If you are missing even one of the values, the equation becomes meaningless. So the fact that really most of the parameters have values which are unknown or unknowable really just makes it a fun thought experiment.

Even if you do not have precise values with well-defined uncertainties, you can try to estimate the numbers. The uncertainty just becomes large.

 

[Ryan_m_b]

Both steps were not the result of single, unlikely events, therefore the involved time-scale cannot be used to compare their probability.
There is nice toy model to show this: Assume that the evolution from "cellular life in some way" to "multicellular life" needs 10^3 major evolution steps in some way. Assume that each step happens randomly at a single time, with an expected time of 1 million years. This is horribly wrong, of course, as there are multiple ways to multicellular life - but it shows the general idea. Using this model, the expected time for the evolution is 1Gy. However, the probability for the process taking less than 0.9Gy or more than 1.1Gy is close to 0. Therefore, you would expect this process on all planets with the same initial conditions and enough time.

That's not how evolution works at all. You acknowledge that there are multiple paths to evolution but have not taken into account how significantly this affects your working out. There are many scenarios where mutations would be positively beneficial but would force an organism up a peak on a fitness landscape that is not conducive to evolution towards multicellularity. This in turn means that future mutations would have a deleterious effect and would not be selected for. In addition you haven't taken into account the changing environmental conditions that would be both biotic and abiotic in origin changing the context for selection.

Lastly you're post has the tone of teleological evolution, this is fallacious. There is no set path in evolution, merely a diverse fitness landscape created by the environmental factors working on the frequency of alleles in a population.

 

[mfb]

As I said, the model is horribly wrong. There is no point in describing all the details how. The main message stays: If an evolution has to consist of many steps (and I am sure that you agree here for the discussed step), the required time is not a good measure for its probability.
Multicellular organisms probably just could not form within 100 million years (with reasonable probability), regardless of the probability of their evolution later.

 

[Ryan_m_b]

As I said, the model is horribly wrong. There is no point in describing all the details how. The main message stays: If an evolution has to consist of many steps (and I am sure that you agree here for the discussed step), the required time is not a good measure for its probability.
Multicellular organisms probably just could not form within 100 million years (with reasonable probability), regardless of the probability of their evolution later.

Possibly but we can't really know for sure (at the moment that is). There may have been perfectly achievable routes that never evolved.

 

[thorium1010]

Multicellular organisms probably just could not form within 100 million years (with reasonable probability), regardless of the probability of their evolution later.

For the majority of geological time of our planet, favored unicellular organisms . Multicellularity is relatively late in this game. It is still not very clear how multicellularity came about. Planets outside our system maynot be so lucky to have similar conditions that favor multicellurarity. It is reasonable to think most planets that can harbor life would contain unicellular organisms. Multicellularity would be much more rare i.e. taking what we have learn t so far from our planet.

 

[mfb]

Sorry, but we are talking about different things.
The point of my posts is: You cannot use the time-scales involved on Earth to estimate the probability of such an evolution.

Do you disagree with that? If yes, why? If not, we have the same opinion in that respect.


As an unrelated topic, I think that the evolution from single cells to multicellular organism needs a lot of time. I do not try to estimate any numbers for that (apart from "<=1Gy is possible" of course). But the difference between simple cells and the task sharing in complex multicellular organism is quite large.

 

[thorium1010]

Sorry, but we are talking about different things.
The point of my posts is: You cannot use the time-scales involved on Earth to estimate the probability of such an evolution.

Do you disagree with that? If yes, why? If not, we have the same opinion in that respect.

My point is we do not know exactly how multicellularity arose on Earth. Timescales or evolution is pretty insignificant in answering this question.

 

[mlagman]

Unfortunately, it seems that the focus of this thread has digressed from what was originally proposed. Regardless, the original posts were rather interesting. I agree that the available data is inadequate to make a truly informed decision in respects to life in the universe. Often times, I find it somewhat offensive when a person asserts that life was created or evolved in a dogmatic way. From my perspective, it is as if someone is saying that they know everything about everything and can now state without objection that life either evolved or was created. Instead, I feel that one should objectively consider what evidence is available, and never settle into one opinion.

 

[mfb]

What are those "evolutionists" you refer to in your pdf?
Are we gravitationalists? Weakinteractionalists? Atomists? (Hey, those exist!)
Are we LHCists because we are highly convinced that the LHC exists?
I think you simply mean "scientists".

Anyway, your claim is wrong, and amino acids were found to be produced naturally in experiments. See the references here for details.

Our current universe, with protons, neutrons, electrons, all those forces and so on appears fine-tuned, but there are two simple explanations:
- maybe many different parameters are realized, in different regions of spacetime or in different universes. In this case, there is no fine-tuning at all: Life simply evolves in places where it is possible, and does not evolve elsewhere.
- maybe different parameters can lead to different systems which allow the evolution of life.Other issues:
1) discussing private pet theories is against the forum rules
2) the pdf has several logical flaws, but (1) prevents me to write a lengthy post about that.

 

[Dotini]

My point is we do not know exactly how multicellularity arose on Earth. Timescales or evolution is pretty insignificant in answering this question.

May I be bold enough to suggest that multicellularity, as an organizing principle in dusty plasmas, was already well established before Earth was formed? Lab experiments have shown several dusty plasma attributes resembling those of biological organisms, such as self-assembled gaseous cell organization, helical structures, self-duplication, evolution, and more.
https://www.physicsforums.com/showthread.php?t=180520

Respectfully submitted,
Steve

 

[ImaLooser]

I mostly agree. When you look at the simply enormous scale of the universe it seems almost silly that there isn't any other life out there.

To me it seems very silly. Egotism and self-importance is only argument against it, as far as I can see.

 

[ImaLooser]

For the majority of geological time of our planet, favored unicellular organisms . Multicellularity is relatively late in this game. It is still not very clear how multicellularity came about. Planets outside our system maynot be so lucky to have similar conditions that favor multicellurarity. It is reasonable to think most planets that can harbor life would contain unicellular organisms. Multicellularity would be much more rare i.e. taking what we have learn t so far from our planet.

Multicellularity does not seem all that big of a deal to me. Bigger is better, and group of cells is better than a big cell because if one cell dies the rest survives.

It's the first cell that baffles me. How did that happen? I'll look at that thread.

 

[Whovian]

Multicellularity does not seem all that big of a deal to me. Bigger is better, and group of cells is better than a big cell because if one cell dies the rest survives.

It's the first cell that baffles me. How did that happen? I'll look at that thread.

Well, I'm about to call on philosophy more than physics.

http://en.wikipedia.org/wiki/Anthropic_principle

 

[ImaLooser]

Well, I'm about to call on philosophy more than physics.

http://en.wikipedia.org/wiki/Anthropic_principle

Humph.

 

[Chronos]

The weak anthropic principle is logically self evident. Parameter space must be restricted to ranges that do not preclude our existence. The strong anthropic principle, IMO, is the sort of logic you would expect from a theologian, not a scientist.

 

[Ryan_m_b]

The weak anthropic principle is logically self evident. Parameter space must be restricted to ranges that do not preclude our existence. The strong anthropic principle, IMO, is the sort of logic you would expect from a theologian, not a scientist.

My signature encapsulates my opinion of the strong anthropic principle.

 

[ImaLooser]

My signature encapsulates my opinion of the strong anthropic principle.

Well expressed.

 

[surajt88]

 

[bohm2]

I came across an interesting thread/post discussing the debate between Carl Sagan and Ernst Mayr that relates to this thread and more so with the probability of intelligent life:

They were debating the possibility of finding intelligent life elsewhere in the universe. And Sagan, speaking from the point of view of an astrophysicist, pointed out that there are innumerable planets just like ours. There is no reason they shouldn’t have developed intelligent life. Mayr, from the point of view of a biologist, argued that it’s very unlikely that we’ll find any. And his reason was, he said, we have exactly one example: Earth. So let’s take a look at Earth. And what he basically argued is that intelligence is a kind of lethal mutation. And he had a good argument. He pointed out that if you take a look at biological success, which is essentially measured by how many of us are there, the organisms that do quite well are those that mutate very quickly, like bacteria, or those that are stuck in a fixed ecological niche, like beetles. They do fine. And they may survive the environmental crisis. But as you go up the scale of what we call intelligence, they are less and less successful. By the time you get to mammals, there are very few of them as compared with, say, insects. By the time you get to humans, the origin of humans may be 100,000 years ago, there is a very small group. We are kind of misled now because there are a lot of humans around, but that’s a matter of a few thousand years, which is meaningless from an evolutionary point of view. His argument was, you’re just not going to find intelligent life elsewhere, and you probably won’t find it here for very long either because it’s just a lethal mutation. He also added, a little bit ominously, that the average life span of a species, of the billions that have existed, is about 100,000 years, which is roughly the length of time that modern humans have existed

.

 

[mfb]

If you see "existence of species" as "success", the number of living animals does not matter. Humans exist, and as long as they do Earth is a species with (quite) intelligent life.

Big animals are less numerous - that is not a matter of intelligence, but a simple scaling with available food, the ability to travel and so on.

We are kind of misled now because there are a lot of humans around, but that’s a matter of a few thousand years, which is meaningless from an evolutionary point of view.

I think exactly this time span shows the success of intelligence in terms of reproduction and survival of individuals.

 

[Ryan_m_b]

If you see "existence of species" as "success", the number of living animals does not matter. Humans exist, and as long as they do Earth is a species with (quite) intelligent life.

Big animals are less numerous - that is not a matter of intelligence, but a simple scaling with available food, the ability to travel and so on.

True but that is why bigger animals are more vulnerable. Relatively small disturbances in a trophic web can cause them to go extinct.

I think exactly this time span shows the success of intelligence in terms of reproduction and survival of individuals.

Bacteria can go from 1 to 7 billion in a matter of days. Point being that "success" has very different meanings and IMO when we talk about the success of intelligent beings we aren't talking abut their numbers or how fast their population doubles.

 

[bohm2]

Here's the relevant arguments by Mayr in more detail:

Can SETI Succeed: Carl Sagan and Ernst Mayr Debate
http://www.astro.umass.edu/~mhanner/Lecture_Notes/Sagan-Mayr.pdf

 

[mfb]

True but that is why bigger animals are more vulnerable. Relatively small disturbances in a trophic web can cause them to go extinct.

And compared to other big animals, humanity is less vulnerable.

Bacteria will likely survive any event on Earth except a full destruction of the crust. When viewed as one big group of life, they are very successful in that respect. But that does not mean that no other group can be successful, too.
Humans are the first species on Earth with the potential to take life to other planets.

Bacteria can go from 1 to 7 billion in a matter of days. Point being that "success" has very different meanings and IMO when we talk about the success of intelligent beings we aren't talking abut their numbers or how fast their population doubles.

The interesting point in the human population growth is not the growth itself, it is the self-made rapid increase in food production and habitable areas.

 

[Scitech]

Equation > Where are they Paradox = High yield Fusion is hard < my original idea too

As it would only take 3 million years may to colonize the Milkyway if mankind had high yield fusion and you only need one such inquisitive race to start intergalactic expansion on a significant scale then either Life is miraculous or High yield Fusion is hard to impossible.

Note, because the solar system is on the move colonization is more likely to look like milk swirls in a coffee cup than a spherical expansion thus the likely hood of any two civs being in close radio or physical contact goes up approx 100 fold.

No doubt genesis is clumpy too, life will spawn near to other within its local 'birth clump' , again more chance to meet so long as life isn't stupendously rare or miraculous.

my 2 cents

 

[mfb]

As it would only take 3 million years may to colonize the Milkyway
[...]
thus the likely hood of any two civs being in close radio or physical contact goes up approx 100 fold.

Do these numbers have any scientific background (if yes: source?) or did you just make them up? They look quite specific.

No doubt genesis is clumpy too, life will spawn near to other within its local 'birth clump'

Why? I have doubts, can you explain this?

Why do fusion power plants imply colonization on a galactic scale?

 

[Scitech]

3 million years , is an oft quoted number for star hopping across the galaxy, you could do it in less, you could do it in more, but its a good mid point time-wise without making to many assumptions that stretch credibility or feasibility

colony ship + long journey + settle down build up period till it can spawn new colonies etc etcThe universe is clumpy at all scales, look out the window or thru a microscope, thus it stands to reason that as galaxies are clumpy and not random that some of those clumps will be more favorable to genesis than othersFact 1 , we know for 100% sure that high yield fusion is not trivial

Fact 2, where are they ?, If life is not miraculous then there must be 1000s if not millions or billions of civilizations in the universe. If Fusion is very hard or impossible they may be mostly isolated and perhaps more prone to extinction as they cannot colonize other system with ease

I don't fancy your chances of inter stellar colonization without access to high yield fusion, its an exceptionally tricky venture

Thus it is highly improbable , indeed nigh on impossible for the universe to be inhabited by 1000s of civilizations all of whom have high yield fusion (and they will know by implication that other races will do to even if they do not meet) and not one of the decides to broadcast hello or colonize the universe...that is an absolute ridiculous assumption to make...it only takes a small % of these to be adventurous, most of space is empty so you might as well make use of it, at the very least you have a defensive buffer zone and made your race extinction proof.So life is near miraculous OR high yield fusion is next to impossible
take yer pick, one or the other, because other themes don't really stand up to scrutiny. While there are 1000s of plausible themes obvious is obvious and simply wipes the board. Give me high yield fusion + a bit of time and ill make Darth Vader look like a garden gnome by comparison. With all that space confetti flying about, 'hello there' or 'lookout they are coming for' you messages would be flooding the airwaves in each and every direction.

If we crack high yield fusion this century or indeed within 1000 years then life must be near miraculous,( exceedingly rare ) ...either that or an exceedingly improbable alternate scenario that explains the silence must somehow true. If you've not considered these matters deeply then there is plenty of scientific literature on the topic

 

[mfb]

3 million years , is an oft quoted number for star hopping across the galaxy, you could do it in less, you could do it in more, but its a good mid point time-wise without making to many assumptions that stretch credibility or feasibility

I would not use the number as an upper limit then.

The universe is clumpy at all scales, look out the window or thru a microscope, thus it stands to reason that as galaxies are clumpy and not random that some of those clumps will be more favorable to genesis than others

The universe is clumpy, but different clumps are often quite similar, so you don't expect that some clumps have a higher probability to get life than other, similar clumps.

Fact 1 , we know for 100% sure that high yield fusion is not trivial

Neither is the detection of gravitational waves, but I do not expect that this will help to establish colonies.

Fact 2, where are they ?, If life is not miraculous then there must be 1000s if not millions or billions of civilizations in the universe.

There are so many possible reasons, some of them are listed here. The evolution of life and a powerful energy source are just 2 points in the list. Other reasons why we did not see extraterrestrial life are listed here, for example.

Maybe many species communicate with each other, and we simply do not see it as most traffic is highly directed and the "hello" broadcasts are not in the tiny frequency ranges where we look for signals.

Fusion power is not magic. It is fuel with very high energy density, but it does not allow you to simply teleport to other stars in no time and no costs.

 

[D English]

Hi Folks, I'm new, very glad I found this place.

It would be shortsighted to think there's no life out there. I dare say there are billions of life-forms on the Earth itself. This shows how prolific life is. Only one life form is capable of contemplating this.

So mathematically, it is a sure bet that life is out there. But also mathematically, it is a sure bet that 99.99999% of that life is not intelligent- as we define it.

I've come to think that any extraterrestrial life that we may be able to communicate meaningfully with does exist, but is so rare, and the expanse of space so vast, that we will never meet.

 

[enceladus_]

I am beginning to think that Earth is an incredible miracle of a planet. Life as developed as ours is an incredible miracle as well.

The Earth survived to incredibly chaotic formation of the solar system. At one point, the Earth was almost destroyed by an impact during this time. Not only that, but it just so happens to coincide in a perfect temperature zone, not too hot, and not too cold. As astronomers and astrophysicists discover more and more planets today, they are finding that the vast majority of them are completely terrible. That alone gives us reason to believe that the Earth is an extremely rare coincidence.

Additionally, Mars appears to be in the past, a planet that was destined for greatness. However, it had one very fatal flaw - it was unable to keep its atmosphere. Because of the solar wind, it was unable to keep its water and life (as we know it) supporting capabilities.

As for life, the origins of life could have come from a comet. From the tests I have seen, it takes a specific type of collision for amino acids on a comet to survive the impact. Life as we know it is very fragile as well. Another aspect that makes the Earth so perfect, is that we have Jupiter to protect us from comets and meteors. A comet or meteor could strike the Earth and completely wipe out life. In the epic span of the universe, human life of planet Earth would be completely meaningless. Only lasting for thousands of years.

There is probably some kind of life on some of the moons in our Solar System, but they will be a far cry from human beings. To me, out form of life is an amazing coincidence, originating from another amazing coincidence, one very low probability event following another.

 

[mfb]

It would be shortsighted to think there's no life out there. I dare say there are billions of life-forms on the Earth itself. This shows how prolific life is. Only one life form is capable of contemplating this.

So mathematically, it is a sure bet that life is out there.

The number of species or living creatures is not (directly) related to the probability that life appears at all.

But also mathematically, it is a sure bet that 99.99999% of that life is not intelligent- as we define it.

How did you get that number?

@enceladus_: It is not surprising that Earth is habitable - otherwise, we would not exist to discover this. Current methods to detect exoplanets are more sensitive to big, hot planets, which do not allow life as we know it. This does not mean that earth-like planets are uncommon, we just do not have the technology to discover most of them yet. Statistical analyses of the Kepler collaboration are promising, and planets with the mass and orbital parameters of Earth around sun-like stars are probably quite common.

Life as we know it is very fragile as well.

I wonder how non-fragile life would look like then. How can life be more robust than "survived every threat in the past 4 billion years"?

 

[adjacent]

Yeah imaginable.Looking into the size of our universe; that is not imaginable.There can be at least one or many life forms.Our technology doesn't let us discover all the universe as a whole I reckon never.Why should someone say we are alone?There are many things yet to be discovered.

 

[enceladus_]

I wonder how non-fragile life would look like then. How can life be more robust than "survived every threat in the past 4 billion years"?

The dinosaurs are extinct, are they not? My point is, it isn't hard for us to be wiped out. In fact, once the Sun begins its red giant death march, all life on this planet will be dead. That will be in a long time, but it is conceivable that life in the past was wiped out due to cosmic events, which would give the impression of their being no life in the present.

 

[Ryan_m_b]

The dinosaurs are extinct, are they not? My point is, it isn't hard for us to be wiped out. In fact, once the Sun begins its red giant death march, all life on this planet will be dead. That will be in a long time, but it is conceivable that life in the past was wiped out due to cosmic events, which would give the impression of their being no life in the present.

Life is inherently hardy even if individual species and ecosystems aren't.

 

[enceladus_]

Life is inherently hardy even if individual species and ecosystems aren't.

Whats hardy? Hardy relative to human beings? It seems that the universe is a brutal overlord.

 

[mfb]

Even if individual species (or even most of them) die out, life continues to exist on Earth => Life on Earth as a whole is hardy.

 

[Ryan_m_b]

What mfb said. Inspite of the several mass extinctions and severe changes the Earth has gone through life was still proliferic.

This thread hasn't really gone anywhere since its starting. All conversations along these lines are hampered by two things: without a complete theory of abiogenesis we don't know what the factors are that allowed life to form on Earth and even if we did our knowledge of other planets is insufficient to work out how likely those factors are to be present.

We can throw around guesses all we like, play numbers games of "if the chance of life is 1 in X" but that doesn't tell us anything.

 

[anorlunda]

Life may be rare. Intelligent life will be rarer. Technological societies rarer still.

I read that if there was no collision that produced Earth's moon, the Earth's crust would be three times thicker. That thickness would be enough to prevent plate tectonics and maybe enough to prevent volcanism. As a result the crust would be poor in heavy elements and metals. Life could have evolved on Earth, even human life, but we might never have created a technological society without metals, or in other words without the moon.

So take the probability of finding earth-like planets to sustain life and multiply that by the probability of having a collision produced moon. The product would be very small.

My point is, there is an enormous gulf between the chances for life and the chances of contacting others.

 

[jim mcnamara]

anorlunda -

This sounds like the Drake equation - http://en.wikipedia.org/wiki/Drake_equation

Also - A lot of what is this thread is really unfounded speculation. Please do not do that.
If you mention something as fact - back it up with a valid citation.

 

[cristo]

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