This article is partly adapted from my TransVision 2007 presentation, “Whither ET? What the failing search for extraterrestrial intelligence tells us about humanity's future.”As I stated in my previous article, “The Fermi Paradox: Back with a vengeance”:
The fact that our Galaxy appears unperturbed is hard to explain. We should be living in a Galaxy that is saturated with intelligence and highly organized. Thus, it may be assumed that intelligent life is rare, or, given our seemingly biophilic Universe, our assumptions about the general behaviour of intelligent civilizations are flawed.So, let’s try to figure out what’s going on. Given the Great Silence, and knowing what we may be capable of in the future, we can start to make some fairly confident assumptions about the developmental characteristics of advanced civilizations.
A paradox is a paradox for a reason: it means there’s something wrong in our thinking.
But rather than describe the possible developmental trajectories of extraterrestrial intelligences (ETI's) (a topic I’ll cover in my next article), I’m going to dismiss some commonly held assumptions about the nature of advanced ETI’s – and by consequence some assumptions about our very own future.
Advanced civilizations do not…
…advertise their presence to the local community or engage in active efforts to contact
As SETI is discovering (but is in denial about), space is not brimming with easily detectable radio signals. SETI’s work during the past 40 years indicates that the quest to detect signals will not be easy.
This problem is not as simple as it sounds. A common apology is that we’ve only recently started our search and we have only scratched the surface. The trouble, however, is that it would be no problem for an ETI to communicate with us if they wanted to.
To do this all they would need to do is seed the Galaxy with Bracewell probes (a self-replicating communications beacon). This scenario was explored in Carl Sagan’s Contact in which a Bracewell probe was lying in wait about 26 light years from Earth in the Vega system. The probe was activated by our radio signals, causing it to direct powerful radio signals at Earth – signals that would not be overlooked.
We know that no such object exists in our solar system or within a radius of about 25 to 50 light years. Our radio activity should have most certainly activated any probe lying dormant in our local vicinity by know. It is also reasonable to assume that if ETI’s embarked on such a communications mission that every solar system would likely have its own Bracewell probe.
Which in turn raises a more troubling question: if ETI’s could construct and distribute probes in this way, why haven’t they gone the extra mile and spread other types of self-replicating devices such as uplift or colonization probes?
…engage in any kind of megascale engineering or stellar re-engineering that is immediately obvious to us within our light cone
All stellar phenomenon that we have observed to this point in time appears ‘natural’ and unmodified. We see no clusters of perfectly aligned stars, nor do we signs of Kardashev III civilizations utilizing the energy output of the entire Milky Way.
As for our light cone, the Milky Way is 100,000 light years in diameter; given the possibility that our Galaxy has been able to support intelligent life for about 4.5 billion years, a 100 million year time lag (at its worst) is not severe enough to cause observational problems (except for distant Galaxies).
…colonize the Galaxy
Our Galaxy remains uncolonized despite the theoretical potential for advanced ETI’s to do so – namely the time and the technology. All that would be required is a self-replicating Von Neumann probe that proliferates outward at an exponential rate. Technologies required to build such a spacecraft would include artificial intelligence, molecular assembling nanotechnology, and an advanced propulsion scheme like anti-matter rockets, beamed energy, or interstellar ram-jets.The reason for non-colonization is not obvious (hence the Fermi Paradox). In addition to technological feasibility there is the issue of economic and sociological imperatives for colonization.
…sterilize the Galaxy
Finally, some good news. We know the Galaxy is not sterile because we exist here on Earth.
Like the colonization potential, the prospect for an advanced ETI to sterilize the Galaxy exists through the use of berserker probes (a term attributed to Fred Saberhagen). These probes could steer NEO’s at planets, unleash nanotechnological phages, or toast planets with directed beams of highly concentrated light.
And like the Bracewell scenario, if a beserker was lying dormant in our solar system it should have destroyed us by now. If sterilization is the goal, there is no good reason for it to wait – particularly as our own civilization hurtles towards a Singularity transition.
Reasons for unleashing fleets of berserkers can be conceived, including xenophobic sociological imperatives or a malign artificial superintelligence (pdf). And all it would take is one civilization to do it. But as Robert Freitas has stated, "The present observational record can only support the much more restricted conclusion that no rapacious galactic civilisations are currently loose in the Galaxy."
…uplift or interact with pre-Singularity intelligences and biospheres
As a civilization that has been left to fend for itself, we have to assume that we, like any other civilization out there, goes it alone. No one is coming to help us. The Great Silence will continue.
Moreover, our presence on Earth and our civilizational development can be explained by naturalistic phenomena. Our existence and ongoing progress has been devoid of extraterrestrial interventions. If we’re going to survive the Singularity, or any other existential risks for that matter, it will have to be of our own devices.
…re-engineer the cosmos
A number of prominent futurists, a list that includes Ray Kurzweil and Hans Moravec, have speculated that the destiny of advanced intelligence is to re-work the cosmos itself. This has been imagined as an ‘intelligence explosion’ as advanced life expands outward into the cosmos like a bubble. The entire Galaxy would be re-organized with much of its matter converted into computronium. Eventually, it is thought that the laws of the Universe will be re-tuned to meet the needs of advanced civilizations.
Unfortunately, we do not appear to inhabit a Universe that even remotely resembles this model. The cosmos appears natural and unperturbed.
This is reminiscent of the God problem and the presence of evil. We live in a Universe that is hostile, indifferent and pointless. If advanced ETI’s had the capacity to re-engineer the Universe such that it was safer, more meaningful and paradisical they would have done so by now. By virtue of the fact that we observe such a dangerous Universe we should probably conclude that such a project is not an option.
In the final part of this series I will make an effort to explain why advanced civilizations don’t do these things and what they might be doing instead.
Part I: Fermi Paradox: Back With a Vengeance
Part III: Fermi Paradox: Possible Solutions and Next Steps
31 comments:
Has anyone considered that technology may NOT be a natural outgrowth of intelligence? If an intelligent society were to remain in balance with its environment (American Indians as a rough example) they may not as aggressively pursue advanced technology as an over-populated, resource-poor, society.
The size of the Milky Way is 100 *thousand* light years, not 100 *million* light years. Even the Local Group of galaxies is only about 10 million light-years in diameter.
This, of course, only emphasizes the point that the light cone effect isn't significant here, but is worth correcting.
It's always possible that we're just the first. Somebody has to be.
Statistically unlikely (though I have a hunch less unlikely than common wisdom seems to think), but it's like the lottery: someone will certainly win, but even the eventual winner reasonably puts his chances at zero prior to the numbers being drawn.
Whoops, thanks for the correction re: size of the Galaxy. I've fixed it.
I think technology is natural; all organisms are lazy in trying to reduce the amount of energy they need to survive.
I guess the issue I have is, could it mean that the technical singularity is unsurvivable?
Osame Kinouchi in Persistence solves Fermi Paradox but challenges SETI projects has proposed a model of colonozation that does not assume that it follows a uniform diffusion process. Instead, he proposes a model for intergalactic colonization that follows the distribution of cities on the Earth. This is not a simple uniform diffusion process, as shown by the non-uniform distribution of cities, and by the presence of exotic "lost" tribes, whose provincial worldview might prompt them to conclude that there is no global civilization.
Kinouchi points out that for a wide class of diffusion processes, including simple models of colonization other than uniform diffusion (in which colonization would occur uniformly in every direction), the number of non-visited sites need not decay exponentially with time. Instead, the probability that some site remains uncolonized might follow a power law.
I'll jump to the conclusion: if the colonization of space follows something like a non-uniform process that we observe on Earth, then there will be large regions of space that won't be colonized, away from the colonized areas.
In that case, since we haven't heard from extraterrestrials, we can assume we are in one of the large, unvisited regions, and so the nearby candidates for SETI searches are also unlikely to have been visited. (Kinouchi asserts that the Fermi Paradox is "locally" true.) So SETI has to look further than the immediate stellar neighborhood.
"Our existence and ongoing progress has been devoid of extraterrestrial interventions."
A pretty contentious point in certain circles. Granted that the best cases are highly elusive and do not provide evidence in the repeatable format that science demands but then again how do you go about observing something smarter than you if it is only interested in being observed on it's own terms?
Shouldn't there be some kind of contingency footnote that at least leaves open the wild possibility that they might be standing beside us in another dimension?
Why does life have to develop technological intelligence, after all of the many possible candidate species here on earth we are the only one that has done that!
See the following paper, Brane Worlds, the Subanthropic Principle and the Undetectability Conjecture for some theories as to why ETI would not be contacting us BUT may be all around us.
I think it's funny how you toss around these various fictitious/theoretical types of probes as if they're reality while completely ignoring the UFO phenomenon we have been observing for decades. It's simply boggling to me how people can dismiss all of the evidence there has been to indicate extraterrestrial visitors in our atmosphere. Sure none of it is concrete to our knowledge but there are so many cases documented, I think it's reasonable to speak on these subjects accordingly. We KNOW intelligent life is out there, theorize on it from there.
I think the Berserker scenario may be the most likely. If life was at one point as widespread as the equations cause us to believe, the Great Silence would indicate that something is working against this.
Given just the first few hundred millions years of advanced life potential in out galaxy way back, it is likely that someone would unleash a self-replicating, exponentially growing berserker system, maybe unable to stop it itself. Once it got going, it would be impossible to stop since anyone who found it would be far behind in numbers, and the berserker had time to evolve to it's maximum possible configuration.
That we are still here may just be a matter of it not having had enough time to fully evaluate and respond to the threat. With that in mind, I'll have another piece of cake now I think...
As they said in the old Pogo comic strip about whether human beings have the most or least advanced brains in the Universe, either way it's a mighty soberin' thought.
To mike's comment about all the UFO "evidence": I think it is more amazing - and more telling - that after thousands of reports for decades or more that nothing really concrete has ever come through.
And please spare me the old war horse about the government hiding alien bodies and crashed spaceships. They have proven that they can't keep a secret if they try. They are certainly no match for superior intellects.
If advanced ETI’s had the capacity to re-engineer the Universe such that it was safer, more meaningful and paradisical they would have done so by now. By virtue of the fact that we observe such a dangerous Universe we should probably conclude that such a project is not an option.
Or alternately, that this has in fact already happened, and the observed universe is so vastly improved that it qualifies to the re-engineering ETIs as "safer, more meaningful and paradisical" - i.e., it all depends on what you are used to.
One possible theory is: rare intelligence.
Life on earth has evolved intelligence above the animal only in homo, and innovating intelligence only in homo sapiens. It's worth considering that even as close-to-human a species as Neanderthals went hundreds of thousands of years without substantially improving on the simple flint knife. As soon as modern humans appeared, we started creating new technologies - starting with art, moving up through weapons, pottery, trade, and culminating in the hunting-agriculture transition that kicked off civilization. There seem to have been no false starts and near misses. It happened once and only once.
That argues for a universe buzzing with life, but in which we never find an ET smarter than a chimp.
If advanced ETI’s had the capacity to re-engineer the Universe such that it was safer, more meaningful and paradisical they would have done so by now.
That sounds to me like parochial thinking.
Assumptions: that ETIs think the status quo is nasty (they might be Taoists), that they consider paradise to be better (there is a vast corpus of sci-fi warning that Eden results in evolutionary regression), that they would intentionally re-engineer it, that they have the means, that they can afford to employ the means, that we would recognize engineering, that we would find the engineering to be an improvement from our own perspective. I could probably continue.
With threats on the scale of berserker probes, its very hard to imagine that ETI, if capable, would take the extreme risk to not launch defense of the same scale.
The lack of any detectable ETI activity whatever is very good evidence for a conclusion that there are none.
Anything else is wishful thinking at this point, akin to religion more than any scientific perspective.
There are no meaningful equations or calculations you can do regarding ETI probability and so forth, because there is no actual data to work with.
Maybe I am wrong and the ETIs are so advanced that they can cloak themselves from detection, and can choose when and if they make contact? Yes, of course. Perhaps as well a god willed all of creation into being in six days. In the end those proposals are equals in their worth for any scientific-minded consideration.
While we have made progress of a sort in our views on alien life and
SETI since its flowering days in the 1960s, we certainly haven't had
much progress in terms of optimism.
For example, look at what this astronomer named Michael Rowan-Robinson
has to say regarding extraterrestrial life:
http://physicsworld.com/cws/article/indepth/30672
Now you might think that a fellow who had a true understanding of
how vast and numerous things are in the Cosmos would not put down
the idea of ETI simply because it hasn't bothered to say Hello to us
yet; but no, he gives this as one of the big reasons why he thinks
there is little intelligent life beyond Earth. Surprising and disappointing.
It seems like a growing trend to me at least. I have noticed a lot of
forums and even published books that, while advocating a brighter
future for humanity via nanotechnology et al, assuming few to none
when it comes to ETI. Obviously arguing that we live in a galaxy
with 400 billion stars 100,000 light years across is not making an
impression even on those who are educated on the subject.
My view on this: It is a combination of fears...
Fear that one's colleagues will not take you seriously (and deny grants) if you
profess belief in little green men, despite decades of progress in astrobiology.
Fear that you will be lumped in with the UFO crowd (okay, that's a legit one).
Fear that there are more powerful and knowledgable beings in the Cosmos,
beings that if they don't attack Earth might still bring us down just by being so
darn superior. After all, we have been God's Chosen Ones for ages; it's tough
to give up a gig like that to a bunch of strange strangers.
Fear that one is not being scientifically rigorous enough. After all, it is true
that we have no solid evidence of alien life of any kind, despite knowing about
hundreds of exoworlds, extremophile life, complex molecules in the Universe, etc.
Plus there's that old Fermi Paradox that keeps getting trotted out every time
this subject comes up. How come THEY haven't visited US? Aren't we the
most visible and important things in all existence?! Ya think just a few other
cultures out there have/had the same thoughts on that topic?
To me it is not very scientific at all that we have done so little searching for
ETI in so few places and declare them non-existant. Sorry that the human
race has such a short attention span and life, but combing 400 billion stars
with our currently technology is going to take a while - and it is entirely
possible that the really advanced ones don't live anywhere near the
visible star systems.
So I say ignore the doubters and the fringe nuts and keep searching.
Remember it was the guys who said humans would never fly who only
talked while the Wright Brothers went out and built their airplanes.
Seems to me there is a very simple (though not very comfortable) set of possible explanations for the non-appearance of ETI which hasn’t been mentioned so far.
First, assume that most/all civilisations manage to get themselves into a global resource/overpopulation/environmental crisis somewhere along their development of a technological society. Then the Universe divides into those civilisations which manage to get past the crisis and get out into the galaxy and those that don’t and head back to the caves. I’m taking no bets on which category the human race will ultimately join, but I will take bets that our present political and social institutions aren’t good enough to solve these problems. Hence, most likely only a minority of civilisations ever get to travel the galaxy.
If those that are travelling the galaxy are only those that have managed to develop more advanced social systems than ours, then I suggest the last thing they would want to do is make contact with us openly. They would be smart enough to know that arriving here and telling us just how primitive our ideas are would get them a nasty reception and probably even trigger off wars or localised violent disputes. [Some years back I wrote a satire describing just this scenario in more detail and showing how only a minority of humanity would accept the aliens in a spirit of goodwill, while most would try to exploit them to maintain their own ‘primitive’ way of life.]
Solution? If we develop similar more advanced social/political systems then maybe they’ll get in touch with us. If we don’t, then we won’t be around long enough – at least in any form that can be called civilised – to play a significant part on the galactic stage.
You say that Bracewell probes should already have been triggered by now, but why should that be? A civilization advanced enough to create self-replicating communications probes may be advanced enough to have discovered means of communication beyond radio - I think it no more likely that we can imagine the physics of 5000 years from now than an ancient Egyptian could imagine our physics.
Actually, the Great Silence may be an indicator that such a communications technology exists. Perhaps the aliens area all around us, but they're using ansibles (or whatever), and mere modulated EM is beneath their notice.
In the last fifteen years twelve hundred Sun-like stars in our vicinity have been scrutinized with ground-based telescopes, and this search has come up with over one hundred extrasolar planets. A particularly promising find was announced in 2002: the planetary system known as 55 Cancri. It is within hailing distance-forty-one light years-from us. Calculations indicate that 55 Cancri could also have rocky planets much like Mars, Venus, and Earth. Many if not most of such planets could harbor life at some point in their evolution. Yet planets capable of harboring the more advanced forms of life could be relatively rare. Most of the solar systems in our neighborhood have alien planets in widely eccentric orbits, moving either too far from their host sun to sustain life or moving too close to it. Yet even if they are relatively rare, given the astronomical number of solar systems in this and other galaxies, the number of extrasolar planets capable of supporting advanced forms of life could still be very large. And even if evolution is relatively slow, taking not millions but a few billion years-complex organisms could still exist on many planets. Some of them could be more evolved than life in our own biosphere, since they could have originated ina more distant past. Considering the time scales of stellar and biological evolution, the habitable zones of planets and related dynamic factors, it is has become the general consensus among leading cosmologists that no less than 5 percent of all solar systems in the universe should be able to support life. That's about 100 billion life bearing planets. Taking into account the possibility that many planetlike objects that are not visible exist in the neighborhood of visible stars-there could be as many as sixty such objects more massive than Mars. In that case, almost every visible star possesses a partially or wholly invisible planetary system. The estimates vary, but the most widely accepted calculations are that there at least 100 billion planetary systems in our own galaxy alone. These highly optimistic estimates are underscored by the fact that many planets could have formed early on in the life of this universe, perhaps on the order of several billion years earlier than the earth.
If the laws of nature hold true throughout the universe, wherever conditions suitable for the evolution of life are present, physical, physical-chemical, and ultimately biological and ecological self-organization is bound to get under way. Life is not likely to be limited to our planet. And given the almost incomprehensible size and age of this universe, it is not all likely to be "stuck" in the protoplasm stage of development. Advanced civilizations likely do exist. But what is most humbling is that the universe is so vastly larger than what we, in our finite capacity as human beings can imagine, even the most advanced beings in the cosmos, beings millions-perhaps even billions of years ahead of us in their intellectual and technological development-may have no more knowledge of our existence than we do of theirs.
In a hundred years or less, the "question" of the existence of intelligent, sentient life forms in the cosmos other than our own may be answered in a much more dramatic way than whatever science fiction can endeavor to speculate currently. For the moment, it makes for great conversation while we wait out the great silence.
Here's the simplest hypothesis...
Intelligent life evolved.
Intelligent life colonizes the Universe.
The Universe we see today, which looks natural, is really the end result of repeated waves of colonization and astroengineering. Keep in mind how well the laws of physics are "tuned" to support our kind of life...
What if what we think is really a natural universe is really the end result of intelligence that evolved long ago.
Do we REALLY know what a colonized galaxy would look like? Or life adapted to spreading through the universe?
Intelligence exists to solve problems. Do we really know what problems an intelligence a billion years ahead of us will need to solve? Or want to solve?
I'm NOT talking about theology, UFO's, quantum mechanical mysticism psychic powers (which obviously don't exist...called the psychic lottery hotline lately?...) but a way to think outside the box.
Ed Sweet
honestly, it would be hard to argue against the fact that life, while probably a "very very rare" phenomenon in the cosmos, could be a singular occurence. But as an astronaut once said of Space, "It's cold and dark". The whole phenomenon that we see occuring now is a psychological phenomenon that exposes the fact that we are not yet an advanced race. It's an incomprehensible escapism for any honest mine. It reeks with our religious collective unconscious. What's truly astronomical are the barriers for an organic being tuned in and created by the energies of a specific atmosphere, which is literally "home for his/her soul" to exist outside of that home, psychological and physiological. It simply makes no sense. And intelligence accepts realities. And ours simply has yet to. As far as the radio signals, my guess is an advanced civilization could very well understand that there must be life elsewhere, maybe they obtained an equation of its inevitability and probability and dropped the issue and 'settled'. All planets have a time-table and nothing lasts forever. It's only desolation that would make such a "reaching out" any sort of priority. And my guess is an advanced civilization would take care of it's own, including its home, so this desperate sort of impetus wouldn't be engendered in its psyches.
1- Human race is not advance. However I have always been suspicious of the fact that over 85% of our technological progress have occurred in the last 200 years. Could it be that we're missing a big chunk of human history and that man has been even more advance in the past and some circulation process (Wars, comet impacts) took him back to pre stone-age time?
2- Everything that we theorize, is based on our observation of the laws of universe. The very building blocks of our logic forces us to believe that things have to have a beginning and an end, all things have to be created by something, cause and effect. What if we stepped into a dimension where our logic would seem totally distorted, "cause and effect" would be de-coupled, things would not have to have had a beginning and so on?
3- Speaking of probes, a type IV civilization is so advance that their manufactured probes could be biological entities just like humans. Makes you think about who you really might be.
4- Could we be alone? It's entirely possible but not probable considering the vastness and age of the universe. We are the product of a combination of and some configuration of a handful of elements such as Hydrogen, Iron and etc. Considering the fact that Universe is made up of the same stuff almost everywhere (Hydrogen and Helium), the very same biological INCIDENT or PROCEDURE that resulted in our creation, is mathematically speaking, very much possible that it can happen somewhere else. So if you're looking for ETs, don't be surprised if they look like us.
5- We have not been able to detect any sign of life within our solar system and further that. Considering that life has been a rare thing at least in our immediate hood, it is entirely possible to assume that life was carried to earth and planted here.
6- As one of our friends here stated, how do we know what a colonized Galaxy is supposed to look like? First of all if a civilization is powerful enough to colonize a galaxy or a solar system, they would be a type IV civilization. To such civilization, us human and our affair, would be as insignificant the affairs of a colony of ANTs is to us! We could very well be just some project of theirs and not even know about it. Once we become advance enough to see what's on the other side of a black hole, once we have a good understanding of knowledge to be able to prove or deny existence of parallel universes of ability of time travel, then and only then, can we even speak about these things without just an speculative imagination!
Could it not be that there is simply a limit to where science and technology can take us? Maybe it is just not possible for any technology advanced enough to travel the stars and make contact. The timescales, areas and physics involved may just make it practically impossible to realise any of this. Advanced ET's could all be just as stuck in their own small spheres of influence as we are no matter how advanced technology and scientific knowledge becomes.
It seems to be that the obvious solution to the Fermi paradox is that the emergence of intelligent life is simply highly improbable. From the fact that we exist, we cannot conclude anything about the probability of intelligent life arising; it could be that only an astronomically tiny fraction of universes like ours ever evolve intelligent life at all. The possible universes without intelligent life simply don't have anyone in them to notice the fact. I.e. our observation of intelligent life being here can be attributed to pure selection bias. From this one data point, you can't put any bounds whatsoever on the log-probability of intelligent life arising. Further, the fact that, in our emergence, we find ourselves roughly halfway through the lifetime of our sun is consistent with the assumption that intelligent life is extremely rare - thus when it occurs, it is just a rare accident, and so one would expect it to occur at a random time during the period of habitability of its planet. Perhaps on most habitable planets, evolution proceeds far slower and life never gets past a primitive stage (microbial, for example). Some significant milestones in our evolutionary history leading up to the emergence of our intelligence may have just happened by accident to occur here much sooner than they would in a random sampling of habitable planets. This theory is testable: As we explore the universe, we should find that planets that get beyond a relatively primitive stage of life are rare.
Study how life evolved on Earth, which is part of an extremely unusual planet/moon system, solar system, highly metalliferous single G2 star system, 2/3 rds of the distance from the dangerous hub of the galactic centre, to the rim, in the relatively safe part of a spiral galaxy, providing the hundreds of millions of years needed for life to evolve to a unicellular level, and the billions of years for multicellular animal life to leave the sea.
Find out about "snowball Earth", (read: Rare Earth: Why Complex Life Is Uncommon in the Universe by Peter Ward and Donald Brownlee; try http://www.amazon.com/ for a copy ) and how for 1.5 - 2 billion years before that, there were only single celled organisms (prokaryotes). My hypothesis is that partially toxic/mutagenic heavy metals, combined with sulphur compounds released by undersea volcanism, were trapped under the ice, permitting single cells floating past in the tidal streams, channelled by that gaseous flow from below, (or possibly just warm currents, rising from the volcanic vent, below) and the ice above, and thereby concentrated into aggregates.
This may well have come about due to surface tension effects on bubbles of gas, moving those well distributed, free floating prokaryotes upward, from their former, more widely scattered, 3D existence, to a semi 2D one, possibly conglomerated between bubbles of gas, or collecting on the undersea surface of the ice above, but warmed by the currents from below, which would have forced them repeatedly into close contact from multiple sides, driving the process, and added some level other important nutrients as well.
It certainly* occurred between a combination of photosynthesising cyanobacteria, and respiring bacteria, probably under thin ice, near the edge, and/or under a "plume". This would have permitted the passage of sufficient sunlight through the ice, to photosynthesising bacteria to continue to produce sugars, while gaining CO2 & nutrients, in the form of waste products from the respiring bacteria. Those sugars, and O2 enabled the respiring bacteria to survive. Those which digested the cyanobacteria perished.
Their remains would then have become available, as additional nutrients, but is not strictly necessary for the purposes of the above. In Antarctica today, lichens (a symbiosis between photosynthesising bacteria, and fungi - interestingly, even today, some types exist which are able to be seperated, yet the cellular processes of others are so inextricably entwined that they are inseperable) still manage to cling to life, under the protective surface of translucent minerals, like quartzite rocks, imparting a green tinge to them.
* See page 122, in section 8, of "Origins of Eukaryotic Cells", in "Life on a Young Planet", by Andrew H. Knoll. Princeton University Press. 2003. ISBN 0-691-00978-3 The evidence is now overwhelmingly in support of that theory, both through cellular structure, and genetically, as well.
The implication of the above is that, although life may well abound throughout the universe, wherever conditions are favourable for long enough, the vast majority will be single celled (prokaryotic) organisms. In the relatively few places where multicellularity evolved, animal life may have existed through mass extinctions long enough to move onto the land, to escape predators, feeding on plants which descended from seaweed, along tidal flats, and rivers.
Take into account the mass extinction which caused the extinction of all true dinosaurs, except birds, thereby enable small mammals to take advantage of the empty ecological niches that came about, as a result, often increasing hugely in size, and diversifying into different habitats, the range of possible candidates for the ultimate evolution of a high degree of intelligence, is very restricted. Of course, we have only the one model to draw on; that of ourselves.
Also note that no primate species, Pan, Australopithecus, or Homo, (including Homo Neanderthalensis) with the single exception of Homo Sapiens Sapiens, has ever progressed further than the technology of the jabbing spear. Chimpanzees (Pan Troglodytes) in the wild have been observed making, and using crude spears.
Using my own updated version of the Drake equation, I estimate that there are/have been/will be only several roughly similar "doppelgangers" of the Earth, at most, in this galaxy. There are thought to be around a hundred billion galaxies, but only a small proportion of those are spiral galaxies, like the Milky Way. When the timing of mass extinctions is taken into account, and the fact that intelligent animals do not necessarily invent, or develop ADVANCED technology, and electronics in particular, (Egyptians, Babylonians, Greeks*, Romans, Chinese, Japanese, Mayans, Aztecs, Toltecs, etc.) I strongly doubt that there will ever be contact with alien races.
Enrico Fermi's "The Great Silence", which is known as the Fermi Paradox, or, simply put: "If intelligent life abounds in the universe, where are they?" seems to be explained by the continued failure of SETI . Of course, this does not mean that the search should be discontinued. They may be too far away for our still crude detectors, or have just evolved, and started sending, 50 light years away, 49 years ago. They may be in a distant galaxy, or on the other side of the Milky Way, obscured by the galactic nucleus.
* The Greeks may have had simple, Direct Current batteries, but they only only seem to have used them for electroplating.
To diverge just a bit: Although we (the top tier of civilization) would like to think that we are an advanced race, I am afraid that we are not. We are not ready for an encounter with any intelligent or unintelligent life form that may be out there. As it is, we can't even get along with our earthly neighbors, be it those in other countries or those in our immediate families. We ravage the environment; try to take advantage of any advances we make (think computer hackers or the financial system) for our own greed; portray ignorance as desirable; kill everything in sight just for the pleasure of it (including our own species); and can't agree on a spiritual constant to guide us toward harmony and peace. I hope that we don't find another living and breathing realm in the outer reaches of space because we would either destroy them outright or keep them in bondage for our arrogant amusement. No, we are not ready. Not yet.
It seems most of you are missing one important point in this. The author keeps referring to ETI's (Extra-Terrsetrial Intelligences), and then assigns activities to these civilizations. Of course these are just conjectures on the author's part, but he is making an assumption that these 'advanced civilizations' would act / react in much the same way as he imagines our own civilization would. In all probability these ETI's are completely unlike us in every fundamental way. The most probable reason we have not detected intelligent life in the universe is that we are unable to recognize the markers of such life. We are, in effect, searching not for Extra-Terrestrial Intelligence, but "human-like" Intelligence. Because that is all we are capable of recognizing at this point in time.
do not.....
exist.
Well, of course one can always contemplate with possibility of being a colony. Very viable method of transporting life is to transport the key ingredients and let it run it's course on a fertile ground.
If you think of colonizing galaxy with life - not specific kind of life but just life, to adopt to the environment however it turns out.
And this has nothing to do intelligent design or other supernatural entities.
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