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Dan,

I can't even begin evaluate the hypothesis from the sketch in that Wikipedia article. I'd have to read the book.

Robert Campbell

Sorry, I should have posted the Amazon.com detail page:

http://www.amazon.com/Medea-Hypothesis-Ultimately-Self-Destructive-Essentials/dp/0691130752/

This might be give you a better idea.

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http://en.wikipedia....edea_Hypothesis

I haven't yet read Ward's book, but would like to see others' reactions to the idea.

Google PETER WARD MASS EXTINCTIONS to enjoy

  • "Asteroid strikes get all the coverage, but "Medea Hypothesis" author Peter Ward argues that most of Earth's mass extinctions were caused by lowly bacteria..."
  • "Peter Ward discusses his hypothesis that mass extinctions have been caused by hydrogen sulfide produced by bacteria in this TED talk. ..."
  • "The current mass extinction has been unfolding for millennia, and unlike the greenhouse effect, global warming, or the hole in the ozone, it is visible without sophisticated imagery or complex computer modeling. It is real, and it is happening to a greater or lesser degree all over the globe; it is most apparent, however, in the tropics. It will not eliminate life from the Earth; no mass extinction does that. But enough species will die that the nature of life on the Earth will be forever changed."
  • "Several times in the distant past, catastrophic extinctions have swept the Earth, causing more than half of all species -from single-celled organisms to awe-inspiring behemoths -to suddenly vanish and be replaced by new life forms. Today the rich diversity of life on the Earth is again in grave danger -and the cause is not a sudden cataclysmic event but rather humankind´s devastation of the environment."

Larry Niven told the same story from the Spaceport Bar. The Chirpstra said that for a billion or so years, they knew an advanced race here on Earth, but the evolution of green plants poisoned the atmosphere and killed them off.

While my own extinction will be a very personal tragedy, life will go on.

In The Future and Its Enemies, Virginia Postrel explodes this myth, embarking on a bold exploration of how progress really occurs. In areas of endeavor ranging from fashion to fisheries, from movies to medicine, from contact lenses to computers, she shows how and why unplanned, open-ended trial and error - not conformity to one central vision - is the key to human betterment. Thus, the true enemies of humanity's future are those who insist on prescribing outcomes in advance, circumventing the process of competition and experiment in favor of their own preconceptions and prejudices.

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I found this link on the above page. See here.

My first thought is that we have only been technologically advanced enough to go to the moon (manned) even though the earth is around 4.5 billion years old. Why would expect other lifeforms in our galaxy, if they exist, to be any more advanced than us? Maybe a million years from NOW one could expect humans (and others?) could colonize the galaxy but I see no reason to expect to see evidence of intelligent life in our galaxy at present.

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In The Future and Its Enemies, Virginia Postrel explodes this myth, embarking on a bold exploration of how progress really occurs. In areas of endeavor ranging from fashion to fisheries, from movies to medicine, from contact lenses to computers, she shows how and why unplanned, open-ended trial and error - not conformity to one central vision - is the key to human betterment. Thus, the true enemies of humanity's future are those who insist on prescribing outcomes in advance, circumventing the process of competition and experiment in favor of their own preconceptions and prejudices.

Ward actually seems to argue -- I read the first two chapters of his book over the weekend -- that technology is key to preventing life from killing itself off. I'm not sure if he's argue for a centrally planned biosphere at this point.

Anyhow, I'm far more interested in seeing if his Medea Hypothesis makes sense and fits the data. I do like that he rightfully calls humans cat food -- well, cat food with some technology.rolleyes.gif

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I found this link on the above page. See here.

My first thought is that we have only been technologically advanced enough to go to the moon (manned) even though the earth is around 4.5 billion years old. Why would expect other lifeforms in our galaxy, if they exist, to be any more advanced than us? Maybe a million years from NOW one could expect humans (and others?) could colonize the galaxy but I see no reason to expect to see evidence of intelligent life in our galaxy at present.

This could a separate discussion -- and a long one at that. The Fermi Paradox rests on the seeming lack of other intelligent life (i.e., humans has not discovered intelligent life elsewhere yet despite the dozens of postcards we sentrolleyes.gif) coupled with the seeming presence of conditions all over the place for such to evolve.

Regarding humans only be able to get to the Moon -- as far as manned spaceflight -- the problem is that you're generalizing from one data point to the whole universe. (Of course, this one example is the problem for all Fermi Paradox speculation. Imagine if you had to similarly explain an absence of some expected outcome from much theoretical speculation coupled with only one data point.) But this example is telling. Humans made it to the Moon four decades ago -- in other words, with technology that older than four decades. It seems not to be pushing the limit to speculate that the reason humans didn't, say, colonize the Moon and move on to Mars or build space habitats is not a technological problem -- as the technology is already decades old.

Let's follow this speculation a little further. Imagine all across the galaxy -- just sticking to this galaxy -- there were also hundreds of other worlds with similar civilizations -- ones capable of space travel and settlement, though not necessarily carrying it out. Out of the hundreds, would you expect every last one to have exactly the same history -- i.e., to develop the technology, do a flags and footprint mission, and decide to focus on other things? Surely, maybe some of them would go that route, but every last one? I think it sounds unlikely -- though, of course, this is just my speculation and I can't present some solid case for my speculation. Let's just say I'm right. If so, some of them should be doing things like moving off world, colonizing other planets, building space habits, and maybe doing megascale engineering projects. I.e., making a racket that everyone else might detect.

Now, let's move this out a bit further. Why would they all start at exactly the same time? Looking over the history of life on Earth, I see a history of catastrophes that seem to have reset the clock a few times -- I mean, being biased here toward intelligent life -- wiped out the most intelligent forms and made, it seems, the rise toward intelligence slip back. Granted, on hundreds of other worlds -- let's say there are literally hundreds of ones with life on them -- complex life might not have evolved or might have faced far worse catastrophes. But it's also possible that Earth is average and some worlds would be above average -- e.g., have better conditions, have fewer catastrophes, have faster evolution toward technological civilization. There's no reason to think it takes 4.5 billion years to get from molten rock to space flight and radio astronomy. (Even if it did, all the worlds probably didn't start exactly 4.5 billion years ago.) I'd expect a least handful to be ahead of the curve (and perhaps a bigger handful to be way behind it -- never getting more than bacteria or being sterile from some really bad luck).

Now ahead of the curve here can mean much. Think if technological civilizations advance at the same rate -- a simplifying assumption as I'd expect different rates of advance. What would a civilization just a hundred years ahead of current human civilization be capable of? I reckon much more than just flags and footprints missions to the Moon -- just as one just a hundred years behind is hardly capable of getting into the air. In fact, some serious estimates are that just being able to get off world and settle space and other planets would, in less than a million years, lead any civilization just expanding at a normal pace -- like some sort of space Polynesians and not necessarily planning to migrate across the stars -- to colonize the whole galaxy. In other words, you wouldn't miss them; they'd be here or close by and certainly making noise enough to be noticed.

So, this brings us back to Fermi Paradox: Where are they? One set of explanations offered is that there's some sort of filter or set of filters that weeds out civilizations, such as Sagan's view that some civilizations develop nuclear weapons and wipe themselves out. I think this links back to the Medea Hypothesis: it might, if true, act as a filter, keeping the the prevalence of life or complex life down enough that it solves the Fermi Paradox. (I'm not saying I agree here -- just trying to present a case for discussion.)

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I found this link on the above page. See here.

My first thought is that we have only been technologically advanced enough to go to the moon (manned) even though the earth is around 4.5 billion years old. Why would expect other lifeforms in our galaxy, if they exist, to be any more advanced than us? Maybe a million years from NOW one could expect humans (and others?) could colonize the galaxy but I see no reason to expect to see evidence of intelligent life in our galaxy at present.

This could a separate discussion -- and a long one at that. The Fermi Paradox rests on the seeming lack of other intelligent life (i.e., humans has not discovered intelligent life elsewhere yet despite the dozens of postcards we sentrolleyes.gif) coupled with the seeming presence of conditions all over the place for such to evolve.

Regarding humans only be able to get to the Moon -- as far as manned spaceflight -- the problem is that you're generalizing from one data point to the whole universe. (Of course, this one example is the problem for all Fermi Paradox speculation. Imagine if you had to similarly explain an absence of some expected outcome from much theoretical speculation coupled with only one data point.) But this example is telling. Humans made it to the Moon four decades ago -- in other words, with technology that older than four decades. It seems not to be pushing the limit to speculate that the reason humans didn't, say, colonize the Moon and move on to Mars or build space habitats is not a technological problem -- as the technology is already decades old.

Let's follow this speculation a little further. Imagine all across the galaxy -- just sticking to this galaxy -- there were also hundreds of other worlds with similar civilizations -- ones capable of space travel and settlement, though not necessarily carrying it out. Out of the hundreds, would you expect every last one to have exactly the same history -- i.e., to develop the technology, do a flags and footprint mission, and decide to focus on other things? Surely, maybe some of them would go that route, but every last one? I think it sounds unlikely -- though, of course, this is just my speculation and I can't present some solid case for my speculation. Let's just say I'm right. If so, some of them should be doing things like moving off world, colonizing other planets, building space habits, and maybe doing megascale engineering projects. I.e., making a racket that everyone else might detect.

Now, let's move this out a bit further. Why would they all start at exactly the same time? Looking over the history of life on Earth, I see a history of catastrophes that seem to have reset the clock a few times -- I mean, being biased here toward intelligent life -- wiped out the most intelligent forms and made, it seems, the rise toward intelligence slip back. Granted, on hundreds of other worlds -- let's say there are literally hundreds of ones with life on them -- complex life might not have evolved or might have faced far worse catastrophes. But it's also possible that Earth is average and some worlds would be above average -- e.g., have better conditions, have fewer catastrophes, have faster evolution toward technological civilization. There's no reason to think it takes 4.5 billion years to get from molten rock to space flight and radio astronomy. (Even if it did, all the worlds probably didn't start exactly 4.5 billion years ago.) I'd expect a least handful to be ahead of the curve (and perhaps a bigger handful to be way behind it -- never getting more than bacteria or being sterile from some really bad luck).

Now ahead of the curve here can mean much. Think if technological civilizations advance at the same rate -- a simplifying assumption as I'd expect different rates of advance. What would a civilization just a hundred years ahead of current human civilization be capable of? I reckon much more than just flags and footprints missions to the Moon -- just as one just a hundred years behind is hardly capable of getting into the air. In fact, some serious estimates are that just being able to get off world and settle space and other planets would, in less than a million years, lead any civilization just expanding at a normal pace -- like some sort of space Polynesians and not necessarily planning to migrate across the stars -- to colonize the whole galaxy. In other words, you wouldn't miss them; they'd be here or close by and certainly making noise enough to be noticed.

So, this brings us back to Fermi Paradox: Where are they? One set of explanations offered is that there's some sort of filter or set of filters that weeds out civilizations, such as Sagan's view that some civilizations develop nuclear weapons and wipe themselves out. I think this links back to the Medea Hypothesis: it might, if true, act as a filter, keeping the the prevalence of life or complex life down enough that it solves the Fermi Paradox. (I'm not saying I agree here -- just trying to present a case for discussion.)

One wrinkle to add to this is that whatever civilizations there are would not all start off at the same point in time. When humans first appeared on Earth, the equivalent life form on Planet A might have already been established and developing for 500,000 years, while on Planet B the same point might not be reached for another two million years. And so forth. So it's possible that there have been plenty of civilizations that went into space but died off millions of years before man appeared here, and it's possible that we are the first species in the universe (or at least the galaxy) to arrive at the point that even limited space travel is possible. Or such civilizations may exist, but too distant for us to know they are there. Consider a civilization that achieved limited space travel (so that it could travel between neighboring planets) half a million years ago. If it is located in a stellars system two million years from us, it will be another 1.5 million years before we can even think about receiving evidence of its existence (through radio signals, etc.). Similarly, that civilization won't receive our first radio signals for not quite another 2 million years.

Jeffrey S.

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I found this link on the above page. See here.

My first thought is that we have only been technologically advanced enough to go to the moon (manned) even though the earth is around 4.5 billion years old. Why would expect other lifeforms in our galaxy, if they exist, to be any more advanced than us? Maybe a million years from NOW one could expect humans (and others?) could colonize the galaxy but I see no reason to expect to see evidence of intelligent life in our galaxy at present.

This could a separate discussion -- and a long one at that. The Fermi Paradox rests on the seeming lack of other intelligent life (i.e., humans has not discovered intelligent life elsewhere yet despite the dozens of postcards we sentrolleyes.gif) coupled with the seeming presence of conditions all over the place for such to evolve.

Regarding humans only be able to get to the Moon -- as far as manned spaceflight -- the problem is that you're generalizing from one data point to the whole universe. (Of course, this one example is the problem for all Fermi Paradox speculation. Imagine if you had to similarly explain an absence of some expected outcome from much theoretical speculation coupled with only one data point.) But this example is telling. Humans made it to the Moon four decades ago -- in other words, with technology that older than four decades. It seems not to be pushing the limit to speculate that the reason humans didn't, say, colonize the Moon and move on to Mars or build space habitats is not a technological problem -- as the technology is already decades old.

Let's follow this speculation a little further. Imagine all across the galaxy -- just sticking to this galaxy -- there were also hundreds of other worlds with similar civilizations -- ones capable of space travel and settlement, though not necessarily carrying it out. Out of the hundreds, would you expect every last one to have exactly the same history -- i.e., to develop the technology, do a flags and footprint mission, and decide to focus on other things? Surely, maybe some of them would go that route, but every last one? I think it sounds unlikely -- though, of course, this is just my speculation and I can't present some solid case for my speculation. Let's just say I'm right. If so, some of them should be doing things like moving off world, colonizing other planets, building space habits, and maybe doing megascale engineering projects. I.e., making a racket that everyone else might detect.

Now, let's move this out a bit further. Why would they all start at exactly the same time? Looking over the history of life on Earth, I see a history of catastrophes that seem to have reset the clock a few times -- I mean, being biased here toward intelligent life -- wiped out the most intelligent forms and made, it seems, the rise toward intelligence slip back. Granted, on hundreds of other worlds -- let's say there are literally hundreds of ones with life on them -- complex life might not have evolved or might have faced far worse catastrophes. But it's also possible that Earth is average and some worlds would be above average -- e.g., have better conditions, have fewer catastrophes, have faster evolution toward technological civilization. There's no reason to think it takes 4.5 billion years to get from molten rock to space flight and radio astronomy. (Even if it did, all the worlds probably didn't start exactly 4.5 billion years ago.) I'd expect a least handful to be ahead of the curve (and perhaps a bigger handful to be way behind it -- never getting more than bacteria or being sterile from some really bad luck).

Now ahead of the curve here can mean much. Think if technological civilizations advance at the same rate -- a simplifying assumption as I'd expect different rates of advance. What would a civilization just a hundred years ahead of current human civilization be capable of? I reckon much more than just flags and footprints missions to the Moon -- just as one just a hundred years behind is hardly capable of getting into the air. In fact, some serious estimates are that just being able to get off world and settle space and other planets would, in less than a million years, lead any civilization just expanding at a normal pace -- like some sort of space Polynesians and not necessarily planning to migrate across the stars -- to colonize the whole galaxy. In other words, you wouldn't miss them; they'd be here or close by and certainly making noise enough to be noticed.

So, this brings us back to Fermi Paradox: Where are they? One set of explanations offered is that there's some sort of filter or set of filters that weeds out civilizations, such as Sagan's view that some civilizations develop nuclear weapons and wipe themselves out. I think this links back to the Medea Hypothesis: it might, if true, act as a filter, keeping the the prevalence of life or complex life down enough that it solves the Fermi Paradox. (I'm not saying I agree here -- just trying to present a case for discussion.)

One wrinkle to add to this is that whatever civilizations there are would not all start off at the same point in time. When humans first appeared on Earth, the equivalent life form on Planet A might have already been established and developing for 500,000 years, while on Planet B the same point might not be reached for another two million years. And so forth. So it's possible that there have been plenty of civilizations that went into space but died off millions of years before man appeared here, and it's possible that we are the first species in the universe (or at least the galaxy) to arrive at the point that even limited space travel is possible. Or such civilizations may exist, but too distant for us to know they are there. Consider a civilization that achieved limited space travel (so that it could travel between neighboring planets) half a million years ago. If it is located in a stellars system two million years from us, it will be another 1.5 million years before we can even think about receiving evidence of its existence (through radio signals, etc.). Similarly, that civilization won't receive our first radio signals for not quite another 2 million years.

Jeffrey S.

I thought I did cover that civilizations might not all start at the same time above, but let's leave that aside.

I think a solution to the paradox that assumes the lack of evidence is explained because other civilizations simply arer not close enough to yet be detected is in danger of making an ad hoc hypothesis -- one that merely fits the data -- and what's more one that can easily be altered so that it can't be tested or falsified. How so? If you wait around, say, 1.5 million years and still don't detect them, then you can revise the hypothesis saying they must be farther away. (Of course, it might actually be the case, but it seems very odd that humans would be first within a certain radius.)

In particular, one would have to ask why only one civilization within whatever range one cares to imagine. (And this sort of proposal has been made before in a more extreme form. Even assuming the universe is infinite, one can imagine civilizations so far apart that they never detect each other. but that seems like assuming there are ghosts but they happen to manifest themselves only when no one's looking.smile.gif) Why only one in such a radius over a certain period of time? And, again, looking at the history of life on Earth it seems quite possible that if life evolved in many other places, in some of those other places it might've gotten to the technological civilization stage much sooner (and in some much latter or not at all).

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I found this link on the above page. See here.

My first thought is that we have only been technologically advanced enough to go to the moon (manned) even though the earth is around 4.5 billion years old. Why would expect other lifeforms in our galaxy, if they exist, to be any more advanced than us? Maybe a million years from NOW one could expect humans (and others?) could colonize the galaxy but I see no reason to expect to see evidence of intelligent life in our galaxy at present.

This could a separate discussion -- and a long one at that. The Fermi Paradox rests on the seeming lack of other intelligent life (i.e., humans has not discovered intelligent life elsewhere yet despite the dozens of postcards we sentrolleyes.gif) coupled with the seeming presence of conditions all over the place for such to evolve.

Regarding humans only be able to get to the Moon -- as far as manned spaceflight -- the problem is that you're generalizing from one data point to the whole universe. (Of course, this one example is the problem for all Fermi Paradox speculation. Imagine if you had to similarly explain an absence of some expected outcome from much theoretical speculation coupled with only one data point.) But this example is telling. Humans made it to the Moon four decades ago -- in other words, with technology that older than four decades. It seems not to be pushing the limit to speculate that the reason humans didn't, say, colonize the Moon and move on to Mars or build space habitats is not a technological problem -- as the technology is already decades old.

Let's follow this speculation a little further. Imagine all across the galaxy -- just sticking to this galaxy -- there were also hundreds of other worlds with similar civilizations -- ones capable of space travel and settlement, though not necessarily carrying it out. Out of the hundreds, would you expect every last one to have exactly the same history -- i.e., to develop the technology, do a flags and footprint mission, and decide to focus on other things? Surely, maybe some of them would go that route, but every last one? I think it sounds unlikely -- though, of course, this is just my speculation and I can't present some solid case for my speculation. Let's just say I'm right. If so, some of them should be doing things like moving off world, colonizing other planets, building space habits, and maybe doing megascale engineering projects. I.e., making a racket that everyone else might detect.

Now, let's move this out a bit further. Why would they all start at exactly the same time? Looking over the history of life on Earth, I see a history of catastrophes that seem to have reset the clock a few times -- I mean, being biased here toward intelligent life -- wiped out the most intelligent forms and made, it seems, the rise toward intelligence slip back. Granted, on hundreds of other worlds -- let's say there are literally hundreds of ones with life on them -- complex life might not have evolved or might have faced far worse catastrophes. But it's also possible that Earth is average and some worlds would be above average -- e.g., have better conditions, have fewer catastrophes, have faster evolution toward technological civilization. There's no reason to think it takes 4.5 billion years to get from molten rock to space flight and radio astronomy. (Even if it did, all the worlds probably didn't start exactly 4.5 billion years ago.) I'd expect a least handful to be ahead of the curve (and perhaps a bigger handful to be way behind it -- never getting more than bacteria or being sterile from some really bad luck).

Now ahead of the curve here can mean much. Think if technological civilizations advance at the same rate -- a simplifying assumption as I'd expect different rates of advance. What would a civilization just a hundred years ahead of current human civilization be capable of? I reckon much more than just flags and footprints missions to the Moon -- just as one just a hundred years behind is hardly capable of getting into the air. In fact, some serious estimates are that just being able to get off world and settle space and other planets would, in less than a million years, lead any civilization just expanding at a normal pace -- like some sort of space Polynesians and not necessarily planning to migrate across the stars -- to colonize the whole galaxy. In other words, you wouldn't miss them; they'd be here or close by and certainly making noise enough to be noticed.

So, this brings us back to Fermi Paradox: Where are they? One set of explanations offered is that there's some sort of filter or set of filters that weeds out civilizations, such as Sagan's view that some civilizations develop nuclear weapons and wipe themselves out. I think this links back to the Medea Hypothesis: it might, if true, act as a filter, keeping the the prevalence of life or complex life down enough that it solves the Fermi Paradox. (I'm not saying I agree here -- just trying to present a case for discussion.)

One wrinkle to add to this is that whatever civilizations there are would not all start off at the same point in time. When humans first appeared on Earth, the equivalent life form on Planet A might have already been established and developing for 500,000 years, while on Planet B the same point might not be reached for another two million years. And so forth. So it's possible that there have been plenty of civilizations that went into space but died off millions of years before man appeared here, and it's possible that we are the first species in the universe (or at least the galaxy) to arrive at the point that even limited space travel is possible. Or such civilizations may exist, but too distant for us to know they are there. Consider a civilization that achieved limited space travel (so that it could travel between neighboring planets) half a million years ago. If it is located in a stellars system two million years from us, it will be another 1.5 million years before we can even think about receiving evidence of its existence (through radio signals, etc.). Similarly, that civilization won't receive our first radio signals for not quite another 2 million years.

Jeffrey S.

I thought I did cover that civilizations might not all start at the same time above, but let's leave that aside.

I think a solution to the paradox that assumes the lack of evidence is explained because other civilizations simply arer not close enough to yet be detected is in danger of making an ad hoc hypothesis -- one that merely fits the data -- and what's more one that can easily be altered so that it can't be tested or falsified. How so? If you wait around, say, 1.5 million years and still don't detect them, then you can revise the hypothesis saying they must be farther away. (Of course, it might actually be the case, but it seems very odd that humans would be first within a certain radius.)

In particular, one would have to ask why only one civilization within whatever range one cares to imagine. (And this sort of proposal has been made before in a more extreme form. Even assuming the universe is infinite, one can imagine civilizations so far apart that they never detect each other. but that seems like assuming there are ghosts but they happen to manifest themselves only when no one's looking.smile.gif) Why only one in such a radius over a certain period of time? And, again, looking at the history of life on Earth it seems quite possible that if life evolved in many other places, in some of those other places it might've gotten to the technological civilization stage much sooner (and in some much latter or not at all).

I was using the 1.5 million years figure as an illustration of the problem, not as a hypothesis.

However, if you think of it, we humans are the first within a certain radius to achieve space travel. The only question is how large is that radius.

Jeffrey S.

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I don't think it's reasonable to assume that intelligent life could evolve much faster than it did on earth. I think when you look at what is required for the evolution from a single dna molecule or whatever to human beings to take place it requires billions of years. For example,

There is evidence that the earliest life on earth may have been thermophilic; needing much hotter temperatures - perhaps 80 degrees - to reproduce. For most of the Earth's history such primitive life forms were all that existed on the Earth. If life began 4 Billion years ago, then for 3.5 Billion, it consisted of such simple life-forms. They lived (and continue to live) up to 3 kilometres under the surface of the earth. Such life forms may be larger in volume than all the other life on Earth.

Only in the last 500 Million years have the larger animals that we are familiar with evolved so the process to get to our stage is long and slow. And what about Mars? Did life begin there and come to earth in an asteroid? It's just possible as Mars almost certainly had water, and life forms such as those deep in the earth's crust could survive inside a chunk of Martian rock. But whether life began here, on Mars or somewhere else is still open to argument.

So theoretically, we have only had 500 million years to evolve from "animals". Similarly, it has only been a few million years since hominids made their appearance. Now why would it be any different on another planet in some other solar system?

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I thought I did cover that civilizations might not all start at the same time above, but let's leave that aside.

I think a solution to the paradox that assumes the lack of evidence is explained because other civilizations simply arer not close enough to yet be detected is in danger of making an ad hoc hypothesis -- one that merely fits the data -- and what's more one that can easily be altered so that it can't be tested or falsified. How so? If you wait around, say, 1.5 million years and still don't detect them, then you can revise the hypothesis saying they must be farther away. (Of course, it might actually be the case, but it seems very odd that humans would be first within a certain radius.)

In particular, one would have to ask why only one civilization within whatever range one cares to imagine. (And this sort of proposal has been made before in a more extreme form. Even assuming the universe is infinite, one can imagine civilizations so far apart that they never detect each other. but that seems like assuming there are ghosts but they happen to manifest themselves only when no one's looking.smile.gif) Why only one in such a radius over a certain period of time? And, again, looking at the history of life on Earth it seems quite possible that if life evolved in many other places, in some of those other places it might've gotten to the technological civilization stage much sooner (and in some much latter or not at all).

I was using the 1.5 million years figure as an illustration of the problem, not as a hypothesis.

However, if you think of it, we humans are the first within a certain radius to achieve space travel. The only question is how large is that radius.

This radius hypothesis -- whatever the radius is -- doesn't tell much. Even your reworking of it might be false. How do you know? Maybe there are space-faring civilizations close by but other factors enter into the picture. What you do know is only that, it seems, such have not been detected. As the absence of detection seems to go against intuition -- the basic intuition being that there should be life and even technological civilizations -- even space-faring ones -- abounding in the galaxy, this gives rise to the need to explain why this is not so.

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I don't think it's reasonable to assume that intelligent life could evolve much faster than it did on earth. I think when you look at what is required for the evolution from a single dna molecule or whatever to human beings to take place it requires billions of years. For example,

There is evidence that the earliest life on earth may have been thermophilic; needing much hotter temperatures - perhaps 80 degrees - to reproduce. For most of the Earth's history such primitive life forms were all that existed on the Earth. If life began 4 Billion years ago, then for 3.5 Billion, it consisted of such simple life-forms. They lived (and continue to live) up to 3 kilometres under the surface of the earth. Such life forms may be larger in volume than all the other life on Earth.

Only in the last 500 Million years have the larger animals that we are familiar with evolved so the process to get to our stage is long and slow. And what about Mars? Did life begin there and come to earth in an asteroid? It's just possible as Mars almost certainly had water, and life forms such as those deep in the earth's crust could survive inside a chunk of Martian rock. But whether life began here, on Mars or somewhere else is still open to argument.

So theoretically, we have only had 500 million years to evolve from "animals". Similarly, it has only been a few million years since hominids made their appearance. Now why would it be any different on another planet in some other solar system?

I disagree. The problem is looking at one history where it takes some number of years to develop something and generalizing to say that this is the only path. It seems to me that, counterfactually, this process might take a longer or a shorter path elsewhere -- unless you posit some other reason why it must always take the same amount of time.

Let's look at another case from Earth bioevolution: the evolution of animal life on land. The first land animals seem to have been arthropods and evidence for them living on land, if only temporarily, dates to about 490 million years ago, but over the next several tens of millions of years, they seem firmly established on land. The first vertebrates on land date to about 100 million years later! This difference of rates in colonizing a new environment should give pause to believing other traits, such as intelligence or technological civilization, should always take roughly the same amount of time.

Think of it! These animals were all descended from pretty much the same lines dating back just maybe a few hundred million years earlier -- in the Cambrian or late Precambrian. So, let's say they all started out from a common ancestor about 600 million years ago. If this is so, then by about 150 million years later, one group was firmly on land, while the other had to wait another 100 million years to do the same -- about two thirds longer in terms of evolution. Why is it so hard, then, to believe intelligence might not, in a different place, follow a different and shorter path?

And think of all the various seemingly random catastrophes that happened along the way. What if, e.g., fewer asteroids had crashed into Earth after, say, the Cambrian? Might this have led to ever more intelligent animals evolving? Or, perhaps, the opposite? Maybe fewer mass extinctions would led to slower overall evolution toward intelligence. Anyhow, it seems highly contingent -- and there's no reason to suspect the same types of contingencies must line up everywhere else in the galaxy or in the known universe in nearly the same way, don't you think?

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Actually, I mentioned this recently somewhere, but one theory about the Earth and moon is that THEY collided and the Earth got quite a bit bigger than Mars, for example. This allowed it to keep it's atmosphere and subsequently life flourished. Now THAT might be an extremely rare event in the development of a solar system which in itself could eliminate countless systems from having life. But given that it does flourish, my argument to you would be that there are too many extinction events in the early stages of planet and life evolution for the sustained evolution required for intelligence to emerge.

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Actually, I mentioned this recently somewhere, but one theory about the Earth and moon is that THEY collided and the Earth got quite a bit bigger than Mars, for example. This allowed it to keep it's atmosphere and subsequently life flourished. Now THAT might be an extremely rare event in the development of a solar system which in itself could eliminate countless systems from having life. But given that it does flourish, my argument to you would be that there are too many extinction events in the early stages of planet and life evolution for the sustained evolution required for intelligence to emerge.

The current hypothesis that Earth-1 collided with a Mars size planet Way Back When. The result was Earth-2 (the one we currently live on) plus enough debris to stick together and become our moon. If Earth-2 had not been made by an accident it is unlikely that intelligent life would have evolved on Earth-1 since it did not have enough mass to hold onto its atmosphere.

Ba'al Chatzaf

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Actually, I mentioned this recently somewhere, but one theory about the Earth and moon is that THEY collided and the Earth got quite a bit bigger than Mars, for example. This allowed it to keep it's atmosphere and subsequently life flourished. Now THAT might be an extremely rare event in the development of a solar system which in itself could eliminate countless systems from having life.

Minor quibble: My understanding is the currently widely accepted theory is that the Earth was hit by a Mars-sized object very early in its history -- like within the first 50 millions or so of Earth's existence. The Moon was flung out from this -- probably as a disk of material that latter coalesced. It's possible the Earth was sterile before this event.

But the point I think you're trying to make is that a rare event could alter the chances of life occurring seems true and only goes along with my view here.

But given that it does flourish, my argument to you would be that there are too many extinction events in the early stages of planet and life evolution for the sustained evolution required for intelligence to emerge.

Let's say we start around 4.5 billion years ago (roughly the age of the Earth) with a million planets that have the potential to have life on them in our galaxy. Do you really believe only one of them would develop a technological civilization? Do you believe that technological civilization on any of them could only arise, if it did at all, after 4.5 billion years and not, say, on some, after 3.5 billion years or 4 billion years or 4.4 billion years? (Realize in my last example that would be technological civilizations arising on some other planets 100 million years before human civilization.) Now you could argue that you don't believe this is so, but I don't it's unreasonable at all to assume this kind of evolution would proceed at different rates in different places -- rather than assume the one example you know of is either the fatest rate possible or sets the standard.

Let me try another analogy. About two or three decades ago, if you'd asked most space scientists what another solar system was likely to be like and how it formed, they'd probably base their answer on what they knew: something like our solar system with rocky inner worlds and gas giants on the edge of the system. This model would also be backed by computer simulations on how solar systems likely formed. The actual observations of extrasolar planets is completely at odds with this. Now one might argue that the means of detection is only able to detect the oddballs, though I doubt anyone circa 1980 or 1990 would have predicted "hot jupiters." They probably wouldn't even think such things possible -- and so would guess we wouldn't detect any of them and would tell us that we'd have to await much more sensitive technology to find the "normal" cold jupiter like the Jupiter we all know and love.

Might not the same logic apply to your view of evolution? You're generalizing from one sample and it seems unlikely that the one example is necessarily average. For all we know, Earth life might be the oddball life -- maybe in taking too long for intelligence to evolve (or maybe in being the first, which would resolve the Fermi Paradox, of course). Until there's more data, I would speculate that wherever Earth life sits in the data, it's probably not likely to tell us much about everywhere else -- save in broad general terms, such as life everywhere is probably in disequilibrium or evolves. But in divining the actual rates and paths of evolution, I think following the one example too closely -- e.g., expecting life on all other planets to follow the same path and timing of developing, say, large-brained, tool-using, gracile, chatty apes -- is likely to mislead rather than illuminate.

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Actually, I mentioned this recently somewhere, but one theory about the Earth and moon is that THEY collided and the Earth got quite a bit bigger than Mars, for example. This allowed it to keep it's atmosphere and subsequently life flourished. Now THAT might be an extremely rare event in the development of a solar system which in itself could eliminate countless systems from having life. But given that it does flourish, my argument to you would be that there are too many extinction events in the early stages of planet and life evolution for the sustained evolution required for intelligence to emerge.

The current hypothesis that Earth-1 collided with a Mars size planet Way Back When. The result was Earth-2 (the one we currently live on) plus enough debris to stick together and become our moon. If Earth-2 had not been made by an accident it is unlikely that intelligent life would have evolved on Earth-1 since it did not have enough mass to hold onto its atmosphere.

Ba'al Chatzaf

And, of course, there's little to believe the same chance events must play out elsewhere to make life or intelligent civilizations. For instance, another set of solar systems might start out with worlds that are just the right size from the end of the formation. Until we have more data, we can't really say, no?

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Let's say we start around 4.5 billion years ago (roughly the age of the Earth) with a million planets that have the potential to have life on them in our galaxy. Do you really believe only one of them would develop a technological civilization? Do you believe that technological civilization on any of them could only arise, if it did at all, after 4.5 billion years and not, say, on some, after 3.5 billion years or 4 billion years or 4.4 billion years? (Realize in my last example that would be technological civilizations arising on some other planets 100 million years before human civilization.) Now you could argue that you don't believe this is so, but I don't it's unreasonable at all to assume this kind of evolution would proceed at different rates in different places -- rather than assume the one example you know of is either the fatest rate possible or sets the standard.

Let me try another analogy. About two or three decades ago, if you'd asked most space scientists what another solar system was likely to be like and how it formed, they'd probably base their answer on what they knew: something like our solar system with rocky inner worlds and gas giants on the edge of the system. This model would also be backed by computer simulations on how solar systems likely formed. The actual observations of extrasolar planets is completely at odds with this. Now one might argue that the means of detection is only able to detect the oddballs, though I doubt anyone circa 1980 or 1990 would have predicted "hot jupiters." They probably wouldn't even think such things possible -- and so would guess we wouldn't detect any of them and would tell us that we'd have to await much more sensitive technology to find the "normal" cold jupiter like the Jupiter we all know and love.

Might not the same logic apply to your view of evolution? You're generalizing from one sample and it seems unlikely that the one example is necessarily average. For all we know, Earth life might be the oddball life -- maybe in taking too long for intelligence to evolve (or maybe in being the first, which would resolve the Fermi Paradox, of course). Until there's more data, I would speculate that wherever Earth life sits in the data, it's probably not likely to tell us much about everywhere else -- save in broad general terms, such as life everywhere is probably in disequilibrium or evolves. But in divining the actual rates and paths of evolution, I think following the one example too closely -- e.g., expecting life on all other planets to follow the same path and timing of developing, say, large-brained, tool-using, gracile, chatty apes -- is likely to mislead rather than illuminate.

You seem to be concentrating on how different things could be in other systems. My point is that there are many, many more ways for there NOT to have intelligent life than there are for it to happen. There are probably innumerous planets in which life started and then fizzled out because conditions could not be sustained, possibly even Mars. I think we have to make the assumption that it requires conditions very similar to what we have here for intelligent life to evolve. If you want to open up the door to all kinds of different life-forms, like in sci-fi books, then anything is possible and it's just a waste of time speculating.

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Let's say we start around 4.5 billion years ago (roughly the age of the Earth) with a million planets that have the potential to have life on them in our galaxy. Do you really believe only one of them would develop a technological civilization? Do you believe that technological civilization on any of them could only arise, if it did at all, after 4.5 billion years and not, say, on some, after 3.5 billion years or 4 billion years or 4.4 billion years? (Realize in my last example that would be technological civilizations arising on some other planets 100 million years before human civilization.) Now you could argue that you don't believe this is so, but I don't it's unreasonable at all to assume this kind of evolution would proceed at different rates in different places -- rather than assume the one example you know of is either the fatest rate possible or sets the standard.

Let me try another analogy. About two or three decades ago, if you'd asked most space scientists what another solar system was likely to be like and how it formed, they'd probably base their answer on what they knew: something like our solar system with rocky inner worlds and gas giants on the edge of the system. This model would also be backed by computer simulations on how solar systems likely formed. The actual observations of extrasolar planets is completely at odds with this. Now one might argue that the means of detection is only able to detect the oddballs, though I doubt anyone circa 1980 or 1990 would have predicted "hot jupiters." They probably wouldn't even think such things possible -- and so would guess we wouldn't detect any of them and would tell us that we'd have to await much more sensitive technology to find the "normal" cold jupiter like the Jupiter we all know and love.

Might not the same logic apply to your view of evolution? You're generalizing from one sample and it seems unlikely that the one example is necessarily average. For all we know, Earth life might be the oddball life -- maybe in taking too long for intelligence to evolve (or maybe in being the first, which would resolve the Fermi Paradox, of course). Until there's more data, I would speculate that wherever Earth life sits in the data, it's probably not likely to tell us much about everywhere else -- save in broad general terms, such as life everywhere is probably in disequilibrium or evolves. But in divining the actual rates and paths of evolution, I think following the one example too closely -- e.g., expecting life on all other planets to follow the same path and timing of developing, say, large-brained, tool-using, gracile, chatty apes -- is likely to mislead rather than illuminate.

You seem to be concentrating on how different things could be in other systems.

Yes, and? I'm trying to avoid generalizing from one example, especially when one sees the follow of this in many other fields, such as planetary science with regard to extrasolar planets.

My point is that there are many, many more ways for there NOT to have intelligent life than there are for it to happen.

I don't disagree, but the problem is finding out what the actual numbers are rather than just making a sweeping generalization. In this case, think of this. There are many more ways for you to not have come in existence than for you to be here. Yet you're here.

There are probably innumerous planets in which life started and then fizzled out because conditions could not be sustained, possibly even Mars.

Yes, but, again, this doesn't tell us the actual numbers. Until there's better data and better theories, there's no telling what the average is, how many planets have life, or how many of these evolve civilizations.

I think we have to make the assumption that it requires conditions very similar to what we have here for intelligent life to evolve. If you want to open up the door to all kinds of different life-forms, like in sci-fi books, then anything is possible and it's just a waste of time speculating.

I don't think there's any reason to make that assumption and I gave what I believe are pretty valid reasons for ditching it, including variable rates of evolution on Earth (between, in the example I used, arthropods and vertabrates colonizing dry land) and extrasolar planets. I didn't just make up some abstract argument here without regard for the data.

And my goal here is not to imagine different life forms for some science fiction novel, but to actually show that the view that evolution must take the same rate -- that it takes 4.5 billions years to make technological civilizations capable of exploring space -- is unreasonable at this point -- given the current state of data and theory.

By the way, this should have been under a different topic. I've actually been working my through Ward's book and he doesn't really discuss the Fermi Paradox in it. Instead, he's focuses on Earth life and how it might be self-destructive. It's not a bad read so far.

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By the way, this should have been under a different topic. I've actually been working my through Ward's book and he doesn't really discuss the Fermi Paradox in it. Instead, he's focuses on Earth life and how it might be self-destructive. It's not a bad read so far.

Yes, sorry I hijacked the thread. cool.gif

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Getting back to The Medea Hypothesis, Ward's view is that life is generally self-destructive because it tends to be Darwinian. That is, he believes, because life is Darwinian -- in the sense of producing more offspring, absorbing more resources, and creating more waste than would lead to stability, it leads to killing itself off in various ways. One wonders, if this is to be believed, why life has lasted 3.8 billion years or so on the planet. That alone would seem to fly in the face of the hypothesis.

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Getting back to The Medea Hypothesis, Ward's view is that life is generally self-destructive because it tends to be Darwinian. That is, he believes, because life is Darwinian -- in the sense of producing more offspring, absorbing more resources, and creating more waste than would lead to stability, it leads to killing itself off in various ways. One wonders, if this is to be believed, why life has lasted 3.8 billion years or so on the planet. That alone would seem to fly in the face of the hypothesis.

Generally quite self-destructive? That seems rather harsh. I would say it's generally relentless in it's effort to reproduce - even to the point of ruining it's environment. But natural bio-diversity makes it so organisms can live off each other's by-products and so there is a balance. This is one of the problems with monocultures.

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Getting back to The Medea Hypothesis, Ward's view is that life is generally self-destructive because it tends to be Darwinian. That is, he believes, because life is Darwinian -- in the sense of producing more offspring, absorbing more resources, and creating more waste than would lead to stability, it leads to killing itself off in various ways. One wonders, if this is to be believed, why life has lasted 3.8 billion years or so on the planet. That alone would seem to fly in the face of the hypothesis.

Generally quite self-destructive? That seems rather harsh. I would say it's generally relentless in it's effort to reproduce - even to the point of ruining it's environment. But natural bio-diversity makes it so organisms can live off each other's by-products and so there is a balance. This is one of the problems with monocultures.

Actually, he argues the opposite: that the biosphere itself is self-destructive. He points to positive feedback loops, such as the release of oxygen, as an example of one group of organisms poisoning the whole biosphere. He gives others examples, too, such as how it appears that life tends to promote the release of methane and carbon dioxide during warming events and their sequestration during cooling events -- leading, in the former case, to greater warming and, in the latter, to greater cooling than would happen otherwise.

He doesn't trace these problems to monoculture, though he's not praising that either.

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Actually, he argues the opposite: that the biosphere itself is self-destructive. He points to positive feedback loops, such as the release of oxygen, as an example of one group of organisms poisoning the whole biosphere. He gives others examples, too, such as how it appears that life tends to promote the release of methane and carbon dioxide during warming events and their sequestration during cooling events -- leading, in the former case, to greater warming and, in the latter, to greater cooling than would happen otherwise.

He doesn't trace these problems to monoculture, though he's not praising that either.

Life isn't perfect but it's tenacious :) Like you said, somehow it managed to hang on for 4 billion years or so - must be doing something right.

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