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RESOLVING THE FERMI PARADOX

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#26 llanitedave

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Posted 13 September 2018 - 05:28 PM

 

2) Most definitely untrue... Evolution is not teleological. It does not have a goal or destination, certainly not intelligence (however it is defined) nor even complexity. This view is properly known as orthogenesis and the current state of evolutionary biology specifically and completely excludes anything like it.

 

Michael

For the short term, and on a smaller scale, I agree here.  But at the largest scales of time and diversity, it does seem to be a real trend.  It's not that any instance of evolution is going to result in greater complexity (whether behavioral or otherwise), but even if you look at evolution as nothing more than a random walk through some morphology or behavior space, the long-term result is that the level of complexity will increase on the high end.

 

The reason for this is a type of selection bias within the set of biological possibilities themselves.  When life originally developed it was close to, it not at, the simplest level of life possible.  There is a lower level of complexity that allows a system to be considered "living".  As far as I know, there is no upper limit that has been identified.  So it's a simple statistical fact that as species evolve and diversity increases, niches open up in more complex levels of organization.

 

As life becomes diverse enough to fill available niches, a species that evolves towards a niche of comparable or lesser complexity may find its success blocked by other species that already exist in those niches.  Niches for higher complexity, however, may be un-occupied, and a species may enter them with some possibility of success.

 

So a trend towards greater biological complexity, and with it higher intelligence, may not be an evolutionary imperative, but it does seem to be a predictable result where additional complexity is an evolutionary possibility.  We can't predict that any specific lineage will evolve in that direction, but there seems a good chance that something will.


 

#27 Procyon

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Posted 13 September 2018 - 09:50 PM

It makes sense though, there is life around but perhaps in the 0.0X% range, and advanced lifeforms also but those are probably in the 0.000000X% range, give or take a few zeros. So yeah, we're pretty unique.

Edited by Procyon, 13 September 2018 - 09:50 PM.

 

#28 Araguaia

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Posted 14 September 2018 - 06:25 AM

1) Not necessarily true and still very much under debate in the scientific community. Evolution is dependent upon mutation and selection. Mutation rates for most populations of most species are generally stable and slow, and it is the rate of mutation that determines the 'speed' of evolution, not the rate of selection. 

 

2) Most definitely untrue... Evolution is not teleological. It does not have a goal or destination, certainly not intelligence (however it is defined) nor even complexity. 

 

1) But we are talking about precisely the sort of environments that generate mutations: too much radiation, hazardous chemistry, etc.  These are the sort of environments life has to deal with initially, before it grows complex enough to generate a full biosphere.

 

2) Of course there is no goal, but there is an outcome.  Most lineages may not grow in complexity, but some will, and over time that accumulates.  Given a few billion years of relative stability there will be more complex life forms, even if most life is still very simple - like here on Earth.


 

#29 nmoushon

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Posted 14 September 2018 - 01:02 PM

I remember reading an article, forget exactly what about, but to sum it up it was saying that one of the biggest things that differentiated *life* from *intelligent life* was that life will live in places that meet its basic needs.( i.e food and shelter) Life will have no desire or will to move to a new area or change its ways unless one of those things changes. (i.e loss of a food/water source or shelter) Where as intelligent life will seek out to change its environment to improve its life. That could be a need or a want type of change. 

 

Sorry I probably butchered trying to sum up that article from memory lol. 

 

My point is, that if this is true and that life evolves with forced change, rather than they willing change, would that not slow down evolution tremendously? Even to the point of basically no evolution, if no major changes occur of course? 

 

Not a scientist so this is more a question that a counter statement.


 

#30 llanitedave

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Posted 15 September 2018 - 01:41 AM

I remember reading an article, forget exactly what about, but to sum it up it was saying that one of the biggest things that differentiated *life* from *intelligent life* was that life will live in places that meet its basic needs.( i.e food and shelter) Life will have no desire or will to move to a new area or change its ways unless one of those things changes. (i.e loss of a food/water source or shelter) Where as intelligent life will seek out to change its environment to improve its life. That could be a need or a want type of change. 

 

Sorry I probably butchered trying to sum up that article from memory lol. 

 

My point is, that if this is true and that life evolves with forced change, rather than they willing change, would that not slow down evolution tremendously? Even to the point of basically no evolution, if no major changes occur of course? 

 

Not a scientist so this is more a question that a counter statement.

But changes always occur.  Some of those changes are geological, some are astronomical, some are caused by life itself.  Life creates new environments as it evolves to adapt to current environments.  There will always be changing selection pressures.

 

There's also genetic drift, which causes changes to the genetic identity of populations purely at random.  I've read this accounts for more total evolution than selection does, although I'm not sure I'm convinced.


 

#31 mlanglois

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Posted 15 September 2018 - 01:26 PM

Re: Araguaia and llanitedave - sorry about combining my response, but there is some definite overlap in your statements.

 

Both of your arguments initially seem plausible, but only at a superficial understanding of evolutionary theory. Evolution is much more complex than most people realize, much more complex than even most college biology courses describe. One of the powers of the theory is that it can be reduced or simplified to a few easily understood propositions. However that reduction necessarily leaves out aspects that are vital to non-trivial discussions, like the paper above. The theory is currently undergoing an increase in complexity (ironic, huh?) because of the integration, or attempted integration, of numerous non-traditional disciples into its core tenets. It is certainly conceivable that if these attempts are successful, then circumstances regarding that road to complexity may change.

 

However, as it stands now, the primary impediments to both your contentions are extinction(s) and over specialization. Also, our only existing laboratory for observing evolution, the Earth, is both limited in sample size but is also undergoing rapid change because of the actions of a single species.

 

llanitedave, you are speculating about a statistical trend over the whole universe from a sample set that is limited in size and duration (the Earth). Your suppositions are merely guesses without data. You 'feel' that it should turn out that way, but nothing about our experience on Earth supports that feeling. Extrapolating that feeling causes you to commit the informal fallacy of faulty generalizations.

 

"The reason for this is a type of selection bias within the set of biological possibilities themselves.   ... Niches for higher complexity, however, may be un-occupied, and a species may enter them with some possibility of success."

 

There's no such thing as a 'niche of higher complexity'. You are confusing complexity with specialization. (Many simple organisms are highly specialized and quite a few very complex organisms are not at all specialized.) Specialization, or over-specialization, is also often a quick road to extinction as it makes species susceptible to ever smaller environmental changes. And it is really the periodic large and small extinctions in history that cause the greatest objection to your position. This leads to...

 

Araguaia: Regarding point 2, this has not ever been a few billion years of relative stability and there never will be; hundreds of thousands of 'stability' may be too much of a stretch. Mass extinction happen over much larger time scales, but smaller extinctions and the waxing and waning of species are shorter term processes as local environments change. Better than 99% of all the species that have existed on Earth have become extinct; that certainly doesn't argue a path toward intelligence, or anything else for that matter.

 

As to point 1, the overall diversity of life on Earth has gone up and down numerous times throughout history and it is arguable if we are currently experiencing Earth's most diverse period.

 

The short of it is that there is no upward progress over the long term; it's a roller coaster of specialization, speciation and extinction.

 

Michael


 

#32 llanitedave

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Posted 15 September 2018 - 08:40 PM

Re: Araguaia and llanitedave - sorry about combining my response, but there is some definite overlap in your statements.

 

Both of your arguments initially seem plausible, but only at a superficial understanding of evolutionary theory. Evolution is much more complex than most people realize, much more complex than even most college biology courses describe. One of the powers of the theory is that it can be reduced or simplified to a few easily understood propositions. However that reduction necessarily leaves out aspects that are vital to non-trivial discussions, like the paper above. The theory is currently undergoing an increase in complexity (ironic, huh?) because of the integration, or attempted integration, of numerous non-traditional disciples into its core tenets. It is certainly conceivable that if these attempts are successful, then circumstances regarding that road to complexity may change.

 

However, as it stands now, the primary impediments to both your contentions are extinction(s) and over specialization. Also, our only existing laboratory for observing evolution, the Earth, is both limited in sample size but is also undergoing rapid change because of the actions of a single species.

 

llanitedave, you are speculating about a statistical trend over the whole universe from a sample set that is limited in size and duration (the Earth). Your suppositions are merely guesses without data. You 'feel' that it should turn out that way, but nothing about our experience on Earth supports that feeling. Extrapolating that feeling causes you to commit the informal fallacy of faulty generalizations.

 

"The reason for this is a type of selection bias within the set of biological possibilities themselves.   ... Niches for higher complexity, however, may be un-occupied, and a species may enter them with some possibility of success."

 

There's no such thing as a 'niche of higher complexity'. You are confusing complexity with specialization. (Many simple organisms are highly specialized and quite a few very complex organisms are not at all specialized.) Specialization, or over-specialization, is also often a quick road to extinction as it makes species susceptible to ever smaller environmental changes. And it is really the periodic large and small extinctions in history that cause the greatest objection to your position. This leads to...

 

Araguaia: Regarding point 2, this has not ever been a few billion years of relative stability and there never will be; hundreds of thousands of 'stability' may be too much of a stretch. Mass extinction happen over much larger time scales, but smaller extinctions and the waxing and waning of species are shorter term processes as local environments change. Better than 99% of all the species that have existed on Earth have become extinct; that certainly doesn't argue a path toward intelligence, or anything else for that matter.

 

As to point 1, the overall diversity of life on Earth has gone up and down numerous times throughout history and it is arguable if we are currently experiencing Earth's most diverse period.

 

The short of it is that there is no upward progress over the long term; it's a roller coaster of specialization, speciation and extinction.

 

Michael

Hi Michael.  I both agree and disagree with what you write.  I'll agree that our treatment of the subject in this thread is superficial.  I disagree that my understanding is -- at least to the extent that the field is so deep and broad that none of us has an understanding that can encompass the whole of it.  I may have poorly worded my arguments, and admittedly I'm not a specialist in the field.  But, as you've pointed out, just because I'm a generalist doesn't mean I have to think about this on a simple level!  I discovered Stephen Jay Gould in the late 1970's, and Richard Dawkins soon after.  I devoured as many of their works as I could.  I'm probably one of the few who has actually read The Structure of Evolutionary Theory.  I've read E.O. Wilson, Daniel Dennett, and others too numerous to mention, I've head the pleasure of being able to engage with Per Ahlberg and Joe Felsenstein while they patiently answered questions.  I have a general understanding of the Neutral Theory, I'm fairly familiar with the fossil record, and I've been accused of being a Tool of Satan by creationists while in my professional capacity.  I even, some years back, wrote a computer program that modeled evolution in a toy manner, defining organisms with selectable traits and mutable genetics, "Sect-shual" selection (thanks, Netnanny!), changeable habitats, and variable life-spans.  The main thing I discovered was that, while genetic traits can be constrained by selection, the actual length of non-coding 'DNA' can increase rapidly if unconstrained, and did.  None of this makes me an expert, of course.  None of it prevents me from being a chump.  But none of it necessarily makes me a chump, either.  So, mantling myself in my best Duning-Kruger robe, I do think I understand enough of this topic at least to make a useful contribution to it.

 

Also, our treatment of the topic is superficial by necessity, because this is an internet discussion forum.  With all due respect to the impatience of Mark Twain and Blaise Pascal, effective brevity requires a lot of time, and if we don't invest that time, our posts are either too long or too misleading. So we make short, general comments that may (or may not) be valid in a larger sense, but might be difficult to defend in detail without a very much longer essay being written.

 

That said, I'll have to first take issue with your remark about the fallacy of generalization.  We all repeat the fact that, when it comes to life in the universe, we have a single data point to deal with.  And this is true, when we're talking about the origin of life.  But in this thread, we're taking that as a given.  We're conceding a relatively common origin of life, and discussing whether or not that life will inevitably evolve towards greater complexity or intelligence.  And from that perspective, we don't have a single data point, we actually have a large number of them.  Every time a lineage branches off and becomes reproductively isolated from its sibling species, there's a new independent experiment in accumulated complexity taking place.  With procaryotes, the picture is more fuzzy because of the ubiquity of Horizontal Gene Transfer, but there seems little doubt that every living thing today, whether bacteria, archea, or eucaryote, is far more complex than the earliest life forms.  It could be argued that this initial increase in complexity had to happen rapidly in order for life to colonize a wider diversity of habitats and prevent its early extinction.  I think there's a case to be made, arm-wavy as it may be at this point, that any planet that has hosted life for some length of cosmic time will by necessity have life that has increased in complexity since its origins.  The alternative is a lifeless planet, or one in which life appears and disappears repeatedly, without ever making much of an impact.  That may actually be the case, but I actually doubt it.

 

The bottom line, and one that you can apply to all of this argument, is simply that there are more possible ways to be complex than there are to be simple.  As I mentioned earlier, the very first living things were probably about as simple as it is possible to be and still be alive.  From that perspective, almost any evolution that takes place is evolution to greater complexity.  And if natural selection exists, and variations occur and are selected for or against, then at that level, there's really no alternative to greater complexity except extinction.  Therefore, if life doesn't go extinct, it becomes more complex, at least more complex than its original version was.


 

#33 llanitedave

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Posted 15 September 2018 - 11:14 PM

I need to address another point, the possibility of there being a limit to the organizational complexity of life.  There's a distinct possibility of this being the case.  Of the procaryotic organisms alive today, there are only two main divisions, bacteria and archea.  There's almost certainly many more types of metabolism or microstructures, or cell wall chemistry that are possible, but only these two versions have survived to the present, if any others ever existed at all.

 

Earth is a fairly big planet, and it contains a huge number and variety of potential habitats and hazards.  If life has become ubiquitous and robust, then there might be rare opportunities for some event leading to a transformation of structure in some lineage, as happened with the origin of eukaryotes.  It's conceivable that some worlds might be smaller or simpler than Earth, and the space for major transformations never happens.  If life is found to exist in Europa's ocean, it shouldn't surprise us if we find it to be no more complex than our bacteria.  But neither should we be surprised if it's gone beyond that.

 

How about multicellularity?  Not necessarily a given, of course, but if that stage is reached, does that mean that life forms will keep becoming more complex?  One thing that makes it hard to determine is the definition of complexity itself, as Michael points out, it can be tough to separate this from specialization.  It's possible to argue that humans are really no more complex than gorillas -- just different.  We contain the same organ systems, very similar DNA, and even a large number of similar behaviors.  We do have different specialties.  With closely related species, it's hard to find much difference in relative complexity.  But over time, these changes become easier to detect.  When we go back to the Cambrian explosion, some 540 million years ago, when all the prototypes of the current phyla were taking form, complexity was across the board less than it is today.  The common ancestors of annelids, molluscs, arthropods, echinoderms, and chordates were fairly simple, wormlike creatures.  Each of these phyla has increased its complexity by embellishing new features on top of the old.  Each of these lineages did it independently.  Chordates did not trigger complexity in insects.The same phenomena occurred in plants.  Once vascular plants began to colonize the land as simple moss-like organisms, they exploded both in diversity and complexity.

 

None of this is a one-off.  There's not a lack of data here, there's a wealth of it.  The evidence remains that as different groups of plants and animals evolve, they don't usually gain complexity, and they don't usually lose it, but sometimes they will do both.  Since there are a lot more simple organisms than there are complex ones, the loss of complexity in one particular branch doesn't have much effect on the overall complexity of life, but an increase in complexity might.  The effect is that the maximum complexity in a population will increase, even if the vast majority of species remain simpler.  And if that increase in complexity comes with greater evolutionary sophistication, and a survival advantage, then that more complex clade will begin to diversify on it's own, and give rise to similarly complex relatives.  At some point the process will repeat itself.  Some lineages in that group will delete features, most will remain similar to the founder, and maybe one will add another embellishment to the existing body structure or behavior.  Then the overall level of biological complexity on the planet goes up again.  Then the real question is, at what point are the complex members of the group the foundation for further evolution, or to what extent are they dead-end outliers?  I don't think you can tell, except in hindsight.  But hindsight shows us that there has been a broad, although not steady, increase in the complexity of life over time.

 

It's very hard to find increases in modern biological complexity, simply because life has already become so complex, and the amount of variation that can occur without a corresponding increase in complexity is vast.  But, the fossil record shows that it has occurred, in numerous lineages, throughout geologic history.  It wasn't a one-time event, and there's no reason to expect it not to continue from time to time.  Not inexorably, not continuously, and not predictably.  But as time goes on, as evolution leads to the slow accumulation of features, there continue to be more ways to become more complex than there are ways to become simpler.

 

Will it last forever?  Of course not.  Michael mentions periods in Earth's history when overall diversity has decreased.  While previous mass extinctions reduced diversity, they didn't lead to much if any reductions in complexity.  Specialists tended to become extinct at the highest rates, but generalists can be just as complex as the specialists, and those that survive become the evolutionary raw material for further specialization and diversification.  Specialists that don't go extinct, can themselves give rise to more generalist descendents if the competition around them suddenly decreases.  It's highly likely that the first creatures with feathers were specialists, and feathers were a novel, specialized feature themselves.  When that feature became hugely successful, its owners could spread, adapt, and give rise to more generations of generalists and specialists.

 

It's true that you can't necessarily extrapolate all of this to any given extraterrestrial planet.    But merely the fact that evolution allows for increases in complexity is a good indication that in environments where there is room for more sophisticated organisms, eventually that sophistication will appear.  The dynamics of variation, selection, and common ancestry powers that trend, and there's no reason why it shouldn't work anywhere that evolution itself works.


 

#34 rekokich

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Posted 16 September 2018 - 02:16 AM

llanitedave, (is it llanite or llanoite?)

 

You made an important point here:
"The bottom line, and one that you can apply to all of this argument, is simply that there are more possible ways to be complex than there are to be simple.  As I mentioned earlier, the very first living things were probably about as simple as it is possible to be and still be alive.  From that perspective, almost any evolution that takes place is evolution to greater complexity.  And if natural selection exists, and variations occur and are selected for or against, then at that level, there's really no alternative to greater complexity except extinction.  Therefore, if life doesn't go extinct, it becomes more complex..."

Genetic mutations randomly produce life forms of both higher and lower complexity. By individual or social effort, some more complex organisms survive because they have a higher probability of adapting to new niches, or to variations in their current environment. Their survival eventually leads to the rise of even more complex organisms, and to the expansion of the biosphere. This gives the impression that evolution has a "design" toward greater complexity, whereas it is simply a universal statistical phenomenon of a branching algorithm, easily demonstrated with a computer program.

You mentioned another interesting issue of "the possibility of there being a limit to the organizational complexity of life."

Life on Earth is presently at the crossroads of two major evolutionary transformations. If the human civilization survives, within the lifetime of our children we will earnestly engage in bioengineering complex organisms designed for specific assignments. We are already doing so with bacteria and algae, and probably with higher animals in some parts of the world. Within the lifetime of our gradchildren, and especially if quantum computers live up to the promise, the human race will also give rise to artificial, autonomous electro-mechanical life forms.

In theory, neither bioengineered nor artificial life forms will have an upper limit to complexity. Their "evolutionary" rate will proceed at a pace billions of times faster than the natural rate, and it will be entirely beyond our capacity to understand the direction and the motivating force behind their expansion. It appears to be a general rule that a lower life form can never fully comprehend the activities of a higher one. A flatworm does not fathom the intentions of a fish. A fish can not conceive the capture by an osprey. A dog can never understand a diesel locomotive.

Assuming Earth is not the single exception in the universe, it is not inconceivable that the transition from "natural" to designed life forms occurred elsewhere. If we ever do meet ETIs, they are very likely not to be biological.

Rudy


 

#35 russell23

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Posted 16 September 2018 - 09:11 AM

You can get to Alpha Centauri in 40 years using a laser sail.  The basic technology is well understood and has been tested on a tiny scale.  The only major challenge is to scale it up.

 

OTOH, altering the biosphere of a planet so that its gas mix, climate, etc. become inhabitable for an alien species is something that takes nature tens or hundreds of millions of years (see: the oxygenation of the Earth by cyanobacteria).  And we are very, very far from understanding what it takes, let alone to be able to do it artificially, in a controlled manner, and thousands of times faster. 

 

The generations that would have to be born and die in wait for an interstellar mission are nothing compared to how many would have to pass before you could take your spacesuit off on another planet.  Look at our political systems: they can't plan anything beyond ten years.  That is why no one went to Mars.  You really think a social species can organize and follow through with hugely expensive projects that will yield no benefits at all for several millenia?

An interesting possibility that may be relevant to the Fermi Paradox is the possibility of habitable worlds with no biosphere but an abiogenetically produced oxygen rich atmosphere.  Most models rely on photolysis of H2O in the upper atmosphere.   However, one interesting model suggests a photochemical reaction near the surface of a planet involving titanium (IV) oxide could do the trick:

 

https://arxiv.org/abs/1509.03123

 

I recently came across this possibility and from the point of view of a species looking to colonize another planet this type of world could make the most sense. Why colonize a world with a full biosphere if it is possible to find worlds with the architecture (hydrological cycle, O2 rich atmosphere, oceans and land) but no contamination from life? 


 

#36 llanitedave

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Posted 16 September 2018 - 12:04 PM

llanitedave, (is it llanite or llanoite?)

 

You made an important point here:
"The bottom line, and one that you can apply to all of this argument, is simply that there are more possible ways to be complex than there are to be simple.  As I mentioned earlier, the very first living things were probably about as simple as it is possible to be and still be alive.  From that perspective, almost any evolution that takes place is evolution to greater complexity.  And if natural selection exists, and variations occur and are selected for or against, then at that level, there's really no alternative to greater complexity except extinction.  Therefore, if life doesn't go extinct, it becomes more complex..."

Genetic mutations randomly produce life forms of both higher and lower complexity. By individual or social effort, some more complex organisms survive because they have a higher probability of adapting to new niches, or to variations in their current environment. Their survival eventually leads to the rise of even more complex organisms, and to the expansion of the biosphere. This gives the impression that evolution has a "design" toward greater complexity, whereas it is simply a universal statistical phenomenon of a branching algorithm, easily demonstrated with a computer program.

You mentioned another interesting issue of "the possibility of there being a limit to the organizational complexity of life."

Life on Earth is presently at the crossroads of two major evolutionary transformations. If the human civilization survives, within the lifetime of our children we will earnestly engage in bioengineering complex organisms designed for specific assignments. We are already doing so with bacteria and algae, and probably with higher animals in some parts of the world. Within the lifetime of our gradchildren, and especially if quantum computers live up to the promise, the human race will also give rise to artificial, autonomous electro-mechanical life forms.

In theory, neither bioengineered nor artificial life forms will have an upper limit to complexity. Their "evolutionary" rate will proceed at a pace billions of times faster than the natural rate, and it will be entirely beyond our capacity to understand the direction and the motivating force behind their expansion. It appears to be a general rule that a lower life form can never fully comprehend the activities of a higher one. A flatworm does not fathom the intentions of a fish. A fish can not conceive the capture by an osprey. A dog can never understand a diesel locomotive.

Assuming Earth is not the single exception in the universe, it is not inconceivable that the transition from "natural" to designed life forms occurred elsewhere. If we ever do meet ETIs, they are very likely not to be biological.

Rudy

It's Llanite!  I've rarely seen it called llanoite, and never by the locals.  Happens to be a rock that's been a favorite of mine for a very long time -- maybe even in geologic time!

 

I agree with you about bio-engineering -- I think.  Technology changes everything.  One thing it doesn't change, though, is the tendency towards diversification, only the speed of it.

 

Assuming that future merging of biological with artificial  features produces another jump in complexity, it's easy to think from our current point of view that it may also lead to an increasing homogeneity, as communication and interactions become more rapid and widespread, more cross-fertilization of both ideas and chromosomes occurs. But there is another step that lies ahead of us, and that's when we start moving beyond Earth and into the outer solar system.

 

Regardless of the benefits of technology, those who can make their homes among the icy bodies of the Oort Cloud are going to exist in extreme isolation.  Distances are vast, travel is slow.  Populations in individual habitats will be relatively small.  In this scenario, we'll find that our descendants respond by creating highly diverse subcultures, idiosyncratic traditions, languages, and moral rules, and value systems equally diverse. 

 

When it comes to combining technology with biology, values account for as much as capability when choosing what features to add, retain, or prohibit.  These values will differ in different parts of the solar system, so our descendants will began to diverge physically as well as culturally.  At some point, the aliens we speak of will actually be our own bio-technological cousins, regardless of whether life has formed on other worlds.


 

#37 llanitedave

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Posted 16 September 2018 - 12:35 PM

An interesting possibility that may be relevant to the Fermi Paradox is the possibility of habitable worlds with no biosphere but an abiogenetically produced oxygen rich atmosphere.  Most models rely on photolysis of H2O in the upper atmosphere.   However, one interesting model suggests a photochemical reaction near the surface of a planet involving titanium (IV) oxide could do the trick:

 

https://arxiv.org/abs/1509.03123

 

I recently came across this possibility and from the point of view of a species looking to colonize another planet this type of world could make the most sense. Why colonize a world with a full biosphere if it is possible to find worlds with the architecture (hydrological cycle, O2 rich atmosphere, oceans and land) but no contamination from life? 

My question is the same as yours, but it's just one step more removed.  A world of the type you mention would require a huge amount of terraforming to make it habitable for humans.  Easier than Mars, certainly, but it would still require much time and effort, if only to introduce familiar organisms to it.  If we want to live an Earthlike lifestyle on an Earthlike planet, we're going to need a healthy diversity of Earthlike soil bacteria, for starters.

 

Also, as I mentioned in an earlier post, I suspect planets like this would be very hard to find.  Most Earth-sized planets, I guess, are going to be either ocean covered, with little or no land, or desert, with few bodies of liquid water.  The hydrological cycle as we know it is, I suspect, an unusual feature, limited to a few "goldilocks planets" with global water volumes almost identical to that of Earth.  Other planets would still have *a* hydrological cycle, but it would be different than the one we know.

 

It's hard to hold these discussions without making a lot of assumptions, and one assumption that I think is necessary when we talk about contact with other worlds in other star systems is the possession of a power supply that at the very least controls a practical nuclear fusion reactor.  Once we do have nuclear fusion, our requirements follow from that.  This is when the icy bodies in the outer reaches of a system become significant.  From them we can get fuel, we can get volatiles, we can get carbon, oxygen, iron, aluminum, nitrogen...  all of the raw materials required for life and technology, and industry.  We don't have to prospect for ore bodies.  Since the cometary worlds are undifferentiated, they haven't sequestered their raw materials into inaccessible layers.

 

And, they don't have deep gravity wells that make it energetically expensive to go elsewhere (although the large separations between them make it temporally expensive!).  But these worlds, and their available resources, outnumber terrestrial planets by as much as trillions to one.  If we're talking about colonizing the galaxy, these places will be where the money is.


 

#38 justfred

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Posted 17 September 2018 - 07:02 AM

This was a fun read. The thing about statistical analysis is that the odds one way or the other are just about always non-zero.People win lotteries and draw to inside straights from time to time. There just might be someone else out there. As to why would our little spot in the universe be interesting enough for them to visit? I don't have a clue. 

 

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#39 Araguaia

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Posted 17 September 2018 - 01:49 PM

 

Araguaia: Regarding point 2, this has not ever been a few billion years of relative stability and there never will be; hundreds of thousands of 'stability' may be too much of a stretch. Mass extinction happen over much larger time scales, but smaller extinctions and the waxing and waning of species are shorter term processes as local environments change. Better than 99% of all the species that have existed on Earth have become extinct; that certainly doesn't argue a path toward intelligence, or anything else for that matter.

By relative stability I mean no 100-km asteroids, no wholesale poisoning of the atmosphere and oceans with something like O2, no supernova going off close by - the kind of event that can actually extinguish 99%+ of life forms on a planet, and leave only the simplest ones - resets evolution back to square one, if you like.  Perhaps Snowball Earth qualifies, but for all we know it didn't affect deep sea vent ecosystems and the like.

 

Even mass extinctions don't wipe out all complex life.  On the contrary - enough complex life survives that in the burst of evolution that follows the extinction you generally get even more complexity.  Not because evolution trends towards that "goal", but due to simple accretion.  Eventually, enough complex organisms generate complex ecosystems - and social systems - which naturally favor ever-more complex evolutionary solutions.

 

None of this results from "direction" in evolution.  Water carves precisely crafted meanders in a floodplain, not because it has that purpose, but because that's how the laws of the Universe makes the grains of sand fall.  Nothing teleological about it.  


 

#40 llanitedave

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Posted 17 September 2018 - 04:16 PM

And just to be clear, while the fact of extinction doesn't argue for a path to intelligence, and doesn't even imply it, it certainly does enable it.  Without species turnover, there would be no room in the environment for new species to appear, whether more complex or not.


 

#41 TOMDEY

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Posted 18 September 2018 - 08:30 AM

Excellent development, Rudy, Alexandra, Andrea! Especially your points regarding plateauing of (the currently exponential) growth of technologies. Indeed, the Universe, which we find ourselves inexorably "stuck" in... seems lavishly understandable, but NOT to limitless extent... to we humans, or anyone else. That limit would be a property of the Universe... NOT the curious observer. And, alas, that natural limit to understandableness seems grossly inadequate to allow for the technologies for us to become, literally... gods.

 

Nother little technical difficulty point here: If one were to, somehow, find a way to transport our fragile bodies at relativistic speeds... the Entire Universe would become, relative to the traveler... HARD radiation! aka entirely hostile and destructive... No free lunch. Call in sick... forever.

 

Many readers would take your conclusions as depressingly pessimistic. But that simply reflects our personal, individual instinct to survive... hence, to fear the Grim Reaper. But, that does NOT, therefore, allow us to impose that instinct on the Universe Itself! It may just be, that what surrounds us... is content to be finite, temporary... mortal.

 

And THAT need not depress!

 

To quote the song:

 

Is that all there is, is that all there is
If that's all there is my friends, then let's keep dancing
Let's break out the booze and have a ball
If that's all there is

Songwriters: Jerry Leiber / Mike Stoller

 

Tom


 

#42 BillP

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Posted 19 September 2018 - 12:27 PM

Nice argument !!  I do have some points to pick though:

 

A) Some of the items you mentioned as "what we know" I feel are still largely "not known".  You said "With relatively high confidence, we know the following"...I numbered them:

1.Life developed very early in the history of our planet.

2.The probability of life increases in proportion to the number of suitable environments.

3.Life is highly adaptable to extreme environments and to competition.

4.Probability of complex organisms increases with the passage of time.

5.Evolutionary pressures favor the emergence of the brain and intelligence.

6.Some intelligent species can develop technology.

7.We have observed that natural laws appear to be universal.

8.We presently know that most, if not all, stars have planetary systems, and that approximately one in five have planets in the habitable zone. There are likely tens of billions of suitable planets in the galaxy, and billions of trillions in the universe.

9.Although we are unique as spiritual individuals, there is nothing exclusive in our collective physical existence as a species."

 

In my estimation, the following are not givens: 1,5,6,8,9.  For #1 - While it is hypothesized that life began early in our history, we still have no knowledge of abiogenesis and there are competing hypotheses such as life started on Earth from interstellar origin. For #5 - I would not say even for the single case of evolution in a planetary ecosystem that we know, Earth, that one can draw that conclusion with any rigor.  Indeed, if the chance arrival of an asteroid that was just the right size so as not to be devastating to all life, but devastating enough to cause the extinction of the then dominant life on the planet, the dinosaurs, mammals would likely never have gained a significant foot hold to eventually become dominant.  For #6 - We only have knowledge of ourselves for this so a case of one is not statistically valid.  For #8 - There is more needed than for the planet to be in a habitable zone.  The star system they are in needs to be exceedingly stable, the geology of the planet needs to be very stable, asteroid and meteor bombardment needs to not be continually disruptive.  So it is much rarer that simply the planets in habitable zones.  Right now there are 20+ planets discovered that are "conservatively" though to be habitable.  So about 24 or the 2400 exoplanets discovered, or 1%.  The Milky Way is estimated to have 100B planets, so maybe 1B are habitable.  But again, habitable now does not mean their star was stable enough over the billions of years for maybe intelligent life to evolve.  And actually, since we do not even know what conditions are needed for abiogenesis, we really have no data to determine what planets might have been suitable for this billions of years ago.  For #9 - the only way to posit that there is nothing exclusive in our collective physical existence as a species is to have a sample of other species from other planets.  Not having that again gives us a case of one to draw conclusions from, which is not valid.

 

B) Your assumption, "Assuming Earth is not singular, but a random sample of habitable environments in the universe, an educated argument in favor of intelligent aliens vastly outweighs any argument against their existence", is a rather big assumption and also a wrong criteria.  For complex or intelligent life to evolve there needs to be a long stable environment on both the planet and its sun.  This is a different criteria from a habitable planet.  We have no knowledge to even guess the number of planets that might have had that history and will not know that until we can examine their geologic records.

 

C) In my reading of current research, my conclusion is just the opposite from yours that: "In fact, astronomers are commonly making discoveries that, compared to other stars in the galaxy, the Solar System and Earth are not exceptional in the physical or chemical sense."  There are many papers out there saying just the opposite and that our location in the galaxy is in a very stable place, not all supernova that seed the interstellar medium produce potassium and luckily the ones that seeded the molecular cloud our star formed from did, etc.  So there is a rarity to the Earth and where we are located in our galaxy that afforded the relatively stable many billion year period so life that did come about could evolve more.

 

Great article and debate position!  Enjoyed it.  From my perspective though there is sufficient evidence in what we presume is needed for long term evolution to happen that demonstrates that indeed Earth is in a much rarer circumstance than the planets we've found so far that are within habitable zones of their stars.  As example, a few years ago everyone got excited about Earth-like exoplanet Proxima Centauri b which is in the habitable zone and so very close.  But we see that is not sufficient as it's star is not so stable: "According to a new study by an international team of scientists, Proxima Centauri released a superflare that was so powerful, it would have been lethal to any life as we know it" (April 12, 2018, Universe Today).


 

#43 llanitedave

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Posted 19 September 2018 - 09:30 PM

Nice argument !!  I do have some points to pick though:

 

A) Some of the items you mentioned as "what we know" I feel are still largely "not known".  You said "With relatively high confidence, we know the following"...I numbered them:

1.Life developed very early in the history of our planet.

2.The probability of life increases in proportion to the number of suitable environments.

3.Life is highly adaptable to extreme environments and to competition.

4.Probability of complex organisms increases with the passage of time.

5.Evolutionary pressures favor the emergence of the brain and intelligence.

6.Some intelligent species can develop technology.

7.We have observed that natural laws appear to be universal.

8.We presently know that most, if not all, stars have planetary systems, and that approximately one in five have planets in the habitable zone. There are likely tens of billions of suitable planets in the galaxy, and billions of trillions in the universe.

9.Although we are unique as spiritual individuals, there is nothing exclusive in our collective physical existence as a species."

 

In my estimation, the following are not givens: 1,5,6,8,9.  For #1 - While it is hypothesized that life began early in our history, we still have no knowledge of abiogenesis and there are competing hypotheses such as life started on Earth from interstellar origin. For #5 - I would not say even for the single case of evolution in a planetary ecosystem that we know, Earth, that one can draw that conclusion with any rigor.  Indeed, if the chance arrival of an asteroid that was just the right size so as not to be devastating to all life, but devastating enough to cause the extinction of the then dominant life on the planet, the dinosaurs, mammals would likely never have gained a significant foot hold to eventually become dominant.  For #6 - We only have knowledge of ourselves for this so a case of one is not statistically valid.  For #8 - There is more needed than for the planet to be in a habitable zone.  The star system they are in needs to be exceedingly stable, the geology of the planet needs to be very stable, asteroid and meteor bombardment needs to not be continually disruptive.  So it is much rarer that simply the planets in habitable zones.  Right now there are 20+ planets discovered that are "conservatively" though to be habitable.  So about 24 or the 2400 exoplanets discovered, or 1%.  The Milky Way is estimated to have 100B planets, so maybe 1B are habitable.  But again, habitable now does not mean their star was stable enough over the billions of years for maybe intelligent life to evolve.  And actually, since we do not even know what conditions are needed for abiogenesis, we really have no data to determine what planets might have been suitable for this billions of years ago.  For #9 - the only way to posit that there is nothing exclusive in our collective physical existence as a species is to have a sample of other species from other planets.  Not having that again gives us a case of one to draw conclusions from, which is not valid.

 

B) Your assumption, "Assuming Earth is not singular, but a random sample of habitable environments in the universe, an educated argument in favor of intelligent aliens vastly outweighs any argument against their existence", is a rather big assumption and also a wrong criteria.  For complex or intelligent life to evolve there needs to be a long stable environment on both the planet and its sun.  This is a different criteria from a habitable planet.  We have no knowledge to even guess the number of planets that might have had that history and will not know that until we can examine their geologic records.

 

C) In my reading of current research, my conclusion is just the opposite from yours that: "In fact, astronomers are commonly making discoveries that, compared to other stars in the galaxy, the Solar System and Earth are not exceptional in the physical or chemical sense."  There are many papers out there saying just the opposite and that our location in the galaxy is in a very stable place, not all supernova that seed the interstellar medium produce potassium and luckily the ones that seeded the molecular cloud our star formed from did, etc.  So there is a rarity to the Earth and where we are located in our galaxy that afforded the relatively stable many billion year period so life that did come about could evolve more.

 

Great article and debate position!  Enjoyed it.  From my perspective though there is sufficient evidence in what we presume is needed for long term evolution to happen that demonstrates that indeed Earth is in a much rarer circumstance than the planets we've found so far that are within habitable zones of their stars.  As example, a few years ago everyone got excited about Earth-like exoplanet Proxima Centauri b which is in the habitable zone and so very close.  But we see that is not sufficient as it's star is not so stable: "According to a new study by an international team of scientists, Proxima Centauri released a superflare that was so powerful, it would have been lethal to any life as we know it" (April 12, 2018, Universe Today).

Good points, Bill.  And responding to them leads us right back to the Drake equation, and its unknown factors that we still need to work on.

 

Some people may not like the Drake equation, and might look for alternatives, but I don't think we're going to really be able to get away from it.


 

#44 rekokich

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Posted 19 September 2018 - 09:31 PM

Bill,

 

Thank you for the detailed analysis of the article, and for your extensive response. Perhaps I need to refine a few points.

I think the article makes it clear that it is not possible to to specify if ETI are common or rare based on a statistical approach founded on only a single sample. However, based on indirect evidence, we think that any allegation that no other intelligent life exists in the galaxy or the visible universe requires extraordinary proof that Earth is a singular case among the estimated hundred billion trillion habitable planets.

The total number of stars with habitable planets is estimated by NASA and ESO to be one in five, which is about 60 billion in our galaxy. The fact that we have observed only about 1% of discovered planets to be in the habitable zone is due to the inadequacy of our observational methods to detect small, rocky planets as efficiently as we detect gas giants, or large planets in tight orbits around a star.

There is no doubt that the evolution of intelligent life requires long periods of a relatively stable environment. I say relatively stable because moderate and even severe disruptions actually promote evolution. Each of the five major extinction events in the last half billion years on Earth was followed by an explosion of new species, far more complex and intelligent than the previous. Had it not been for the Cretaceous asteroid impact 65 million years ago, the most intelligent life form on Earth might have the brains of a chicken. Even apocalyptic disasters, short of disintegrating the planet, are not likely to exterminate all life. Extremophiles, endoliths, and species around deep ocean hydrothermal vents are still likely to survive and eventually recolonize Earth.

In view of your valid objections, I should rephrase the list of indirect evidence in favor of extraterrestrial life as follows:

1) Life APPEARED very early in the history of our planet WHETHER BY ABIOGENESIS OR PANSPERMIA.

It might be effectively argued that panspermia could lead to even wider distribution of life than abiogenesis.

5) Evolutionary pressures ON EARTH favor the emergence of the brain and intelligence.

This is self evident. Unless we assume a singular Earth, the same process occurs elsewhere.

 

6) This item does not need change. Some intelligent species can develop technology. Numerous branches of human predecessors used technology. Apes, monkeys, birds, and cephalopods use simple tools. Numerous animals and insects build very complex structures which boggle scientists' minds. Intelligence, social organization, and genetic variability inevitably lead to "invention", whether conscious or instinctive.

 

8) We presently know that most, if not all, stars have planetary systems, and that approximately one in five have planets in the habitable zone. There are likely tens of billions of suitable planets in the galaxy, and billions of trillions in the universe.

I would not change this item, although I fully agree that continuous catastrophies would severely disrupt evolution toward an intelligent, technological species. There is no implication here that all, or even many, habitable planets bear ETI.

9) Although we are unique as spiritual individuals, there is nothing exclusive in our collective physical existence as a species ON EARTH.

C) ... astronomers are commonly making discoveries that, compared to MOST other POPULATION I stars in the galaxy, the Solar System and Earth are not exceptional in the physical or chemical sense.

We already discussed environmental instability. I agree that the probability of rocky planets and life as we know it is minimal in early, low metallicity Population II stars. I am not aware of any prevalent scarcity of potassium in population I stars. In fact it is one of the most abundant elements, formed by multiple mechanisms:
-supernova nucleosynthesis through neon burning and oxygen burning processes,
-slow neutron capture process in the red-giant AGB stars.
-cosmic ray spallation of iron and copper.

Thank you for your input, Bill. I enjoy speculating on this subject, even if I am never likely to learn the actual truth.

Rudy


 

#45 Araguaia

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Posted 20 September 2018 - 04:50 AM

 

5.Evolutionary pressures favor the emergence of the brain and intelligence.

 

 For #5 - I would not say even for the single case of evolution in a planetary ecosystem that we know, Earth, that one can draw that conclusion with any rigor.  

 

 

Intelligence evolved independently multiple times on Earth.  In Mammalia, starting from relatively low-intelligence ancestors, high intelligence appeared in primates, elephants, and cetaceans - note how different their physiology and ecological needs are - the only thing in common is longevity and social structure.

 

It also appeared in octopuses, whose lineage diverged from ours in the Paleozoic or earlier.  And it now seems that dinosaurs were quite intelligent for reptiles, as many modern birds still are.  The asteroid merely replaced one intelligent group with another.

 

Intelligence is universally useful because it allows organisms to live in social groups, communicate, store and draw upon an extended memory of previous experiences, and most important, adapt to change or new environments much faster than if reliant on genetic adaptation.  Like body armor, large size, speed, and other similar traits, it can be expected to emerge wherever evolution is churning unhindered. 

 

About planetary habitability, no matter how tiny a percentage of planets are in the right zone, with no flares, supernovae, supermassive asteroids, or the like, we are talking about a small percentage of hundreds of billions.  If only 0.1% are habitable and of those, only 0.1% have evolved intelligent life, that is still hundreds of thousands...


 

#46 BillP

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Posted 20 September 2018 - 01:09 PM

The total number of stars with habitable planets is estimated by NASA and ESO to be one in five, which is about 60 billion in our galaxy. The fact that we have observed only about 1% of discovered planets to be in the habitable zone is due to the inadequacy of our observational methods to detect small, rocky planets as efficiently as we detect gas giants, or large planets in tight orbits around a star.

 

I find it very interesting and very telling that NASA/ESO would be saying something like 20% habitable.  It flies in the face of the "actual" data they have gathered.  Very true that we've not observed any significant portion of stars with planets. nor have we searched in all directions.  So we only have a thin slice of the sky where we've had the technology to look well.  Regardless of how small of an area we've searched, if we've only seen 1% of the planets in that search meet the habitable requirement, how in science could they extrapolate that for all the sky it would be 20%??  I think that larger number might be something more based in optimism rather than fact, and it probably has some pressure in the name of funding and maintaining popular interest and support as well.  I prefer to work with knowns rather than add unverified assumptions in order to make the picture more rosey.  The Kepler telescope has provided us with real data to extrapolate, so IMO it is lower risk and more realistic to work from this known data.  But again, just because a planet sits in its star's habitable zone at the current time, does not mean that over the planet's life it had 1) the proper conditions for abiogenesis, and 2) a history of a stable enough environment to support the flourishing and evolution of life if it ever did begin.  So just knowing the percent of planets that will probably be in a habitable zone is not sufficient to say that life would have had a chance to survive, thrive, grow, and evolve.  Until we discover the exact conditions that allow abiogenesis, and until we've surveyed enough habitable planets to determine if their history has been stable enough to support flourishing and evolving of life, I think we pretty much need to make a considered assumption that probably much less than a full 100% of the planets currently in habitable zones.


 

#47 BillP

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Posted 20 September 2018 - 01:22 PM

Intelligence evolved independently multiple times on Earth.

 

I do not disagree with what you state.  However, I think your post overall demonstrates that there needs to be a firm definition of what "intelligence" means.  If this is not done, then the argument the OP is making can easily get interpreted incorrectly.

 

For me personally, a dog, cat, octopus, and others I would say are of "limited" intelligence, or strongly bounded intelligence.  Humans on the other hand have demonstrated that their capacity for intelligence, while not unbounded, is certainly many levels unbounded compared to other creatures on Earth.  I am using the standard definition of intelligence as: the ability to acquire and apply knowledge and skills.

 

So based on the definition, yes a dog can acquire acquire knowledge and build skills to apply it.  But how much knowledge they can accquire then apply is extremely limited.  I've not come across any other life form on Earth that can radically alter their own environment for specific purposes of sustainable creating shelter, food, tools, medicine, manufacturing, etc. with specific argued and agreed upon shared goals.  So it is this specific class of intelligence that is IMO the goal to determine what the reasonable possibility may be to happen in the universe.


 

#48 llanitedave

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Posted 20 September 2018 - 02:20 PM



Intelligence evolved independently multiple times on Earth.  In Mammalia, starting from relatively low-intelligence ancestors, high intelligence appeared in primates, elephants, and cetaceans - note how different their physiology and ecological needs are - the only thing in common is longevity and social structure.

 

It also appeared in octopuses, whose lineage diverged from ours in the Paleozoic or earlier.  And it now seems that dinosaurs were quite intelligent for reptiles, as many modern birds still are.  The asteroid merely replaced one intelligent group with another.

 

Intelligence is universally useful because it allows organisms to live in social groups, communicate, store and draw upon an extended memory of previous experiences, and most important, adapt to change or new environments much faster than if reliant on genetic adaptation.  Like body armor, large size, speed, and other similar traits, it can be expected to emerge wherever evolution is churning unhindered. 

 

About planetary habitability, no matter how tiny a percentage of planets are in the right zone, with no flares, supernovae, supermassive asteroids, or the like, we are talking about a small percentage of hundreds of billions.  If only 0.1% are habitable and of those, only 0.1% have evolved intelligent life, that is still hundreds of thousands...

I'd just put a couple of minor caveats on that.  I wouldn't say dinosaurs were (or birds are) intelligent as a group, but a very few individual lineages were evolving in that direction.  Sauropods, ankylosaurs, ceratopsians, hadrosaurs, as far as I know, don't show any general trend towards intelligence.  A few of the raptors do.  There are certainly some intelligent birds, such as corvids and parrots, but there are a lot of "bird brains" too.

 

So I wouldn't go so far as to say intelligence is universally useful, otherwise it would be a more ubiquitous trait rather than an occasional one.  It's a very metabolically expensive feature, which means the tradeoffs for it to be advantageous would have to be fairly high.

 

Your point is valid, though.  As long as the environment is complicated enough, and as long as the inhabitants have pre-evolved to an adequate level of complexity, intelligence can be expected to pop up from time to time.  And it doesn't necessarily have to do it very often for one group to arise that's intelligent enough to discover technology, language, and culture.


 

#49 BillP

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Posted 20 September 2018 - 02:28 PM

This is good, but still think some of them need to be detailed a little more so not so open ended.  Made comments in blue below.

 

In view of your valid objections, I should rephrase the list of indirect evidence in favor of extraterrestrial life as follows:

1) Life APPEARED very early in the history of our planet WHETHER BY ABIOGENESIS OR PANSPERMIA.

It might be effectively argued that panspermia could lead to even wider distribution of life than abiogenesis.  Agree.

5) Evolutionary pressures ON EARTH favor the emergence of the brain and intelligence.  I would be careful here.  Plants do not have brains or nerveous systems, yet they certainly fall within the classical definition as having "intelligence" - https://www.forbes.c...t/#2401a1dc76dc.  I think it would be better to state the assumption as just "Evolutionary pressures on Earth-life seems to favor the emergence of intelligence."

This is self evident. Unless we assume a singular Earth, the same process occurs elsewhere.  I said "Earth-life" above because I think it is too much of a leap to assume that all life in the universe, if there is other life out there, must behave in the same way it does on Earth.  I think it is not self evident in a non-singluar Earth context that evolutionary processes and pressure will work the same way for all life types. 

 

6) This item does not need change. Some intelligent species can develop technology. Numerous branches of human predecessors used technology. Apes, monkeys, birds, and cephalopods use simple tools. Numerous animals and insects build very complex structures which boggle scientists' minds. Intelligence, social organization, and genetic variability inevitably lead to "invention", whether conscious or instinctive.  I can agree with this I think.  However, "technology" is very broad.  Using a stick is technology, but the level of intelligence there is not sufficient to get you to industrialization.  In the context of what we are trying to determine, I think there needs to be some delineation of technology into classes.  If I am wanting to try to get a good estimate of technological covilizations, I want to know how many have "high" level technology.  As example, ants utilize technology, and they even plant and harvest so they do agriculture as well.  So they have intelligence and learned how to harvest and grow certain plant foods in mini-farms, then harvest them for needed food.  So they created processes which is also a form of technology.  I do not think we want to estimate simply life using technology, but life using technology at the level we use technology. 

 

8) We presently know that most, if not all, stars have planetary systems, and that approximately one in five have planets in the habitable zone. There are likely tens of billions of suitable planets in the galaxy, and billions of trillions in the universe.  I would entirely do not agree with this because the Keppler data says otherwise.  I am also curious where you got this from specifically.  The NASA Kepler site says: "Kepler data suggests that one in five stars like the sun is home to a planet up to twice the size of Earth".  So this is 1 in 5, but that is a very narrow and is only that high for stars like our Sun!  Again, the total data from Kepler's missions shows out of 2,327 confirmed planets, 30 are in the habitable zone, so a tad more than 1%.  This is the real data and what we should be extrapolating from.  Now Wikipedia says that "astronomers" estimated based on Kepler data 40 billion possible habitable planets in Milky Way, but I certainly would not accept that wild number given the actual Kepler data shows such a smaller percent from its field of planets.  Kepler's mission was to monitor 150,000 specific stars (all different types) for exoplanets.  So they found 30 habitable planets so far from 150,000 stars.  So if using those stats instead of planet total vs. habitable the percentage is even smaller.  Again, I think the Wiki "scientists" were a little optimistic and wanted to fan up public suipport for continued interest and funding.  Finding 30 habitable planets across 150,000 stars is only .02%.  Of course, they still have candidates as not finished processing all the data they collected.

I would not change this item, although I fully agree that continuous catastrophies would severely disrupt evolution toward an intelligent, technological species. There is no implication here that all, or even many, habitable planets bear ETI.

9) Although we are unique as spiritual individuals, there is nothing exclusive in our collective physical existence as a species ON EARTH.  Do you even need this assumption?  I think it just muddies things up.  Humans are distinct from other species on Earth as our intelligence is a quantum level above all the other species.  How and why we are the only species here like that is a little bit of a red flag for me that there is something unique or rare on how evolutionary pressures just forced that on us and not all the other species here.  In any event, I feel the evolutionary pressures to intelligence is sufficient and this one just muddies things.

C) ... astronomers are commonly making discoveries that, compared to MOST other POPULATION I stars in the galaxy, the Solar System and Earth are not exceptional in the physical or chemical sense. I still have a problem with this.  Yes we know there are exoplanets but in reality we do not know much about them at all.  We certainly know little to nothing about the geology or atmospheres on them.  So can't really say that most planets are physically or chemically the same.  That is a leap of faith without real data.


 

#50 llanitedave

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Posted 20 September 2018 - 02:30 PM

I do not disagree with what you state.  However, I think your post overall demonstrates that there needs to be a firm definition of what "intelligence" means.  If this is not done, then the argument the OP is making can easily get interpreted incorrectly.

 

For me personally, a dog, cat, octopus, and others I would say are of "limited" intelligence, or strongly bounded intelligence.  Humans on the other hand have demonstrated that their capacity for intelligence, while not unbounded, is certainly many levels unbounded compared to other creatures on Earth.  I am using the standard definition of intelligence as: the ability to acquire and apply knowledge and skills.

 

So based on the definition, yes a dog can acquire acquire knowledge and build skills to apply it.  But how much knowledge they can accquire then apply is extremely limited.  I've not come across any other life form on Earth that can radically alter their own environment for specific purposes of sustainable creating shelter, food, tools, medicine, manufacturing, etc. with specific argued and agreed upon shared goals.  So it is this specific class of intelligence that is IMO the goal to determine what the reasonable possibility may be to happen in the universe.

There were a couple, but they were closely related to us, and we either out-bred them or simply killed them.

 

But you're right, it takes more than "mere intelligence" to make a species that we could communicate with across the void of space.  And after all this, we still don't know how many, if any, of those are out there.


 


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