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“Are We Typical?” — paper by Hartle & Srednicki


Here are some extracts from a recent paper by James Hartle and Mark Srednicki at arXiv.org. So, if we’re not typical, are we special? And is our specialness more than just having big brains and being successful at passing on our genes?

ABSTRACT: Bayesian probability theory is used to analyze the oft-made assumption that humans are typical observers in the universe. Some theoretical calculations make the selection fallacy that we are randomly chosen from a class of objects by some physical process, despite the absence of any evidence for such a process, or any observational evidence favoring our typicality. It is possible to favor theories in which we are typical by appropriately choosing their prior probabilities, but such assumptions should be made explicit to avoid confusion.

To compute likelihoods as though we had been randomly selected by some physical process, when there is no evidence for such a process, commits what might be called the selection fallacy. We are not a disembodied entity that was randomly selected to have a particular physical description; instead, we are the meaning of a transcription of ‘we’ into the language of physical theory….

At present, there are no observational data supporting an assumption that we are typical in some class of observers, and our understanding of biological evolution is insufficient to supply a theoretical justification through the likelihoods. Many calculations that produce likelihoods that favor our typicality do so via the selection fallacy; this can lead to absurd conclusions….

Wakefield, If a theory is true, then we can not blame anyone for finding it and promulgating it. If that theory has some deleterious effects on society then we have to recognize it and deal with it. Something like nuclear fission comes to mind. When a theory is bogus and is promulgated and the theory has some deleterious effects, then the proper way to deal with it first is to denounce the theory. Instead we have a bogus theory promulgated as ultimate truth with some obvious social effects as a result of that promulgation. On top of that any objections to the theory on either scientific or social grounds is suppressed either through censorship or mocking. Where do you stand on this censorship and mocking? jerry
Wakefield, The problem with the macro-evolution is just micro-evolution over deep time is that it is like a magic act. It accomplished it without a trace. Especially since the magic act ran every day in every corner of the world. The analogy of using most of our languages evolving from Indo European is often used but here we actually have records of many of the morphings of one language into another and can see it changing in isolated places in the world at this very moment. If micro evolution to macro evolution did something similar it did so invisibly and with no current examples of a progression going on now in the world. It is like someone changed the language ad hoc and then all started to speak it at once forgetting the old language. Ask your buddies why evolution does not seem to be happening today. Sure the forces of nature have not changed. If there were examples, we would not hear the end of it from the Darwinists. jerry
Wakefield A hundred years ago travelling faster than the speed of sound was thought absurd and they'd put you away in a funny farm if you thought men could fly to the moon and back. Times change. Laser driven light sails are thought able to reach 0.1C but antimatter is the real ticket to attaining over 0.9c. It's really just an engineering problem which means time and money (no fundamental discovery). But before we go any farther you need to know the limits of what's possible within the laws of physics and the resources available in our own solar system. Once nanotechnology has been harnessed and we can exploit the massive resources in our own solar system then interstellar travel becomes a reasonable proposition. 'Tis true there's no getting around the elapsed time on earth for anyone making a round trip but history is littered with examples of people who've left everything behind knowing they'd never see home again. You'd have no lack of volunteers for such epic voyages. As to the limits of the possible go here, read the book (it's free and online now), and then let's talk. I read it 20 years ago when it was hot off the press in hardcover. It's the single most profound book I've ever read. On the question of whether macroevolution is just microevolution but more of it, that remains to be demonstrated. Things don't always scale in a linear fashion ad infinitum. In fact they usually don't. Engineers know this and have to deal with it constantly in just about everything. Many things scale linearly within a limited range but don't over unlimited ranges. You'd think biologists would be more aware of that given it's the reason ants can't grow to the size of elephants and even if they could they wouldn't be able to pick up and carry things 20 times their own weight. Or do they know that? Maybe I give them more credit than they deserve. DaveScot
Mr. Scot: Thank you for your replies. As far as the "terraforming" of other worlds as an escape hatch to this one going sour at some point (which I also understand will happen a few billion years hence), I think one thorn here is that while it doesn't violate the laws of physics to travel to other star systems, it is beyond the pale as an idea. Even at the speed of light, for most theoretical habitable planets if you don't find one in the local neighborhood (about 50 light years) you are talking about a journey for which absurdity is only the beginning of the problem. Few people have a real comprehension of "light year" and what kinds of stupendous energy and resources would be required to make a round trip journey that would preclude coming home an embalmed, irradiated skeleton and having everyone you know having been dead for decades or longer. Probably we've reached the upper limit of our abilities if not knowledge. Even the mighty eagles don't fly into ocean, and fish don't fly with the sparrows. There are certain realms that seem almost designed to be off ludicrously off-limits. I've never heard a good reason for this either, as it is almost akin to some kind of Sith Lord version of what a Devious Designer would do to the Universe. But not the Lord. The Psalms may declare the glory of the Heavens, but the problem here is that many of the things we now know were not even known to the ancients, including the author of Psalms. Hubble, not Hebrews, or St. Paul, is what has opened things up, along with fiendishly complicated mathematics. My agnostic friends howl all the time about how utterly absurd it is to have us puny humans inhabiting a second rate star in such a large universe when most of it is in point of fact invisible, or was for most of human history. This is like being locked in the maid's broom closet at the massive 53 room Biltmore Estate in Asheville and never getting to see the Trophy Room or even the Pantry except from a peephole. Grand Design, they ask? On behalf of whom? For habitable worlds, your best bet might be to let the Drake Equation alone for a whole since we don't know if "habitable planet" parameters are that loose or even more ticky, and just transform Venus. It doesn't have to be 900 F. That's due to pressure of the carbon dioxide more so than just CO2 percentage of the atmosphere (a nightmare for Al Gore in its own Venusion greenhouse). But we can fix THAT easier than traveling the stars. Venus is 64 million miles from the Sun. It could be toned down to say, the weather of Hawaii after some carbon sequestration. As far as this "well duh" moment and "sparing me" the insistence of "Darwin fanatics" trying to hammer simpleton notions of "change" over people heads, I submit to you the issue is not that simple. Let me hop on board the Magical Devil's Advocate Soapbox here, ignore my fun-squelching instincts, and suggest that perhaps the reason "the Darwinists" are so agitated is twofold: First, as it is all but admitted by you and Dr. Behe and Dr. Dembski that "mico-evolution"--a.k.a. "change due to or with changing environments/niches", for which you provided the "well duh", "everybody knows that", mathematical formula. And? Well, neither the NCSE nor the NEA, nor the National Science Foundation, nor the National Association of Biology Teachers, seems to think the issue is "settled" quite so nicely. A quick cruise of "Darwinian" sites indicates that micro evolution invariably leads to MACRO evolution. The difference is time and sheer magnitude of the accumulation of the micro changes, not the essence of what is happening. Likewise, they say, by analogy there is no true "micro gravity" (at least not on the same planet) vs. "MACRO" gravity. No one claims that a soda can falling off a table is possible YET that when it comes to the moon revolving around the earth, some other "supernatural" principle must be invoked, nor a Moon Designer or Clockwinder to keep things in motion. Gravity is just gravity. The difference in simple falling and flamboyant crashes that leave massive craters, is generally the size of the objects and the distance traveled, not the force acting upon them. At least within the same gravitation zone. Small objects orbit the earth as well--including objects the size of soda cans. Likewise they will tell you that the difference in Micro changes vs. Macro evolution is a difference with no real distinction other than time and morphospace of what the creature ends up looking like. Second, this very terminology, "Darwinist". Or worse, "Evolutionist."? Laughable God critics like the cartoonish Richard Dawkins, or William Provine, might relish the term "Darwinian Spear Carrier", as David Berlinski once called him. But most biologists prefer the terms of their trade in the subdivision disciplines without the implication of something conspiratorial or cabal. Imagine the recoil, if not silliness, if we copied the lingo used by the Bible Belt types for practitioners of modern biology, and applied that to other fields and said that geologists were trying to push their seedy "Plate Tectonics Agenda" onto an unwilling public. Dear Lord, what are the Tectonians up to NEXT in our schools, what with all those impersonal forces grinding rocks and killing people in California. Will the scandal never end? Don't they know that only God moves mountains, and says so in his Word? What if geologists were labeled the Oil Boys? Or what if Astronomers got tagged with being "Starry eyed", "Gravitationists", or Hubble Heads, or Kepler Cretins, or Galilean Gullibles? What if physicists were ...Planckians? Or Heisenbergians? Or Copenhagenians? Or the Half-Dead Flux Box Cats? Paleontologists would be Boneheads, or Grave Digging Spear Carriers? I understand, of course, that beyond killing people on rare occasions, Plate Tectonics had more issues settled early on, and far less philosophical baggage to tug around than SOME in the bio sciences. It's true that evolutionary thinking can be used or abused to make some kind of political or social statement about the world or religion. That's regrettable but not really at issue for our purposes here. And not Charles Darwin's fault. Many have tried to make some kind of grand metaphysical story out of "materialist" science in physics as well as biology and the current rage of "sociobiology". So what? The results of this kind of thinking (Gould went in the direction of social change via semisweet Marxism, while Dawkins is politically correct to the hilt) are goofy and contradictory and pose no challenge to practical philosophers truly concerned with humankind, nor any political scientists, nor any real sociologists, nor for that matter any village theologian armed with Biblical history and real faith and its applications. Sincerely, --Wakefield Tolbert Atlanta Ga. S Wakefield Tolbert
Wakefield If evolution doesn't produce an intelligent species which can master spaceflight then it's an evolutionary dead end. All planets eventually become inhospitable to life. I don't think it's any accident at all that humans are building telescopes that can locate planets around other stars that can support life and building transport vessels that can escape the earth and sun's gravity fields. If life on this planet doesn't relocate then its lifespan is about half over as in another 4 billion years or so the sun will turn into a red giant and cook the earth to a crisp. The earth will bear life no more. That might not seem important to us as it's so distant in the future yet we still build telescopes and spacecraft. My opinion is we don't have a choice. Gaining the technology to escape this rock is a biological imperative that's older than our planet. DaveScot
Fit and strong aren't necessarily synomous and the meanings vary in context. Natural Selection is just as bad as it easily implies nature makes some kind of pantheistic conscious decisions. Serendipitous Selection or Survival of the Luckiest would be more apt. The best term by far IMO is Differential Reproduction. Regardless of whether it's luck or fitness, selection or chance, Differential Reproduction objectively and unambiguously describes it. DaveScot
DS: "If survival of the fittest were the rule we shouldn’t be here." I apologise if paraphrasing this to "only the fittest survive" was incorrect. Please correct me if I'm mistaken. The reason that I rephrased it was that as you show, Darwin did use the phrase "survival of the fittest" - it's just that the phrase has very different connotations these days, which is why "it is not generally used by biologists, who almost exclusively prefer to use the phrase "natural selection" All I was concerned with was clarifying a common misconception of Darwinism which says "survival of the fittest" == "survival of the strongest" == "only the strongest survive", which clearly is not a cornerstone of Darwinian theory. Phevans
Wakefield Phevans misquoted me. I didn't write "only the fittest survive". I wrote "survival of the fittest". I don't know if that was an intentional strawman or a careless mistake. He then went to claim it wasn't what Darwinism has to say. I then pointed out that Darwin himself used the terms "Natural Selection" and "Survival of the Fittest" interchangeably, used both in Origin of Species beginning with the fifth edition in 1869 saying "Survival of the Fittest" was even better at describing his theory than "Natural Selection". If Phevans is saying natural selection (or the alternative Survival of the Fittest specifically endorsed by Darwin as equivalent of better) isn't a cornerstone of Darwinian evolution he's sadly misinformed and has been corrected. Of course fitness changes in the context of changing environments. Who here doesn't know that? RM+NS is a simple concept. Darwin fanatics want to present it like rocket science or brain surgery that only the initiated elite may properly understand through many years of study. What bunkum. I don't want to fisk your entire long response but mitochondrial origin from a bacterial ancestor is purely hypothetical and even that's giving it too much credit as hypotheses in science include a means, at least in principle, of verification or falsification which are then employed to promote it to theory or discard it as incorrect. Endosymbiosis is, like the vast majority of evolutionary biology, a guess based on circumstantial evidence. It will never be more or less than that unless and until someone offers a way in principle of either verifying or falsifying it. Less kindly put it's pseudo-science and so is most of the rest of so-called evolutionary "theory" where the evidence that can confirm or deny is irrevocably lost in the annals of deep time. Evolutionary Origin of Mitochondria
Mitochondria do not contain anywhere near the amount of DNA needed to code for all mitochondria-specific proteins, however, a billion or so years of evolution could account for a progressive loss of independence. The endosymbiotic hypothesis might be called a theory, but experimental evidence can't be provided to test it. Only circumstantial evidence is available in support of the proposal, which is the most likely explanation for the origin of mitochondria. The evidence needed to change the model from hypothesis to theory is likely forever lost in antiquity.
Moreover, I have no idea why Margulis is getting credit for the endosymbiosis hypothesis. It was first proposed by R. Altmann in Die Elementarorganismen und ihre Beziehungen zu den Zellen (Viet, Leipzig, 1890) over a century ago. Nothing more than an antique microscope is needed to see that mitochondria look and act like a trapped bacterium. Again we have Darwin fanatics trying to make simple observations and easily made deductions into proverbial rocket science. Spare me. DaveScot
Dave Scott and Phevans. From one "theo" type to two whom I understand are not--Thanks for your responses. Dave, I'm not sure you understood Phevans about niche filling vs. "survival of the fittest." Are you saying these terms are what we laymen call "the distinction without a difference"? I agree with you that we are fighting the prokaryote pals left and right these days--and probably for the last several hundred million years. These were the roaches before there were roaches, and even harder to swat. So, touché--about the prokaryotes. And maybe that's all we can expect on Gleise-like worlds. Except for one little nag: As one biology professor explained to us younglings years ago, "these things that live in your guts are more 'contemporaneous' than YOU are". These organisms HAVE changed. They don't just simply fall in place in the human gut, but got there by hook and crook starting with their own embedding into each other things like mitochondria (see Lynn Margulis for this one, much as she was mocked for the idea early on...) and on to other creatures, etc. How else to go from inhabiting merely ponds to inhabiting every other creature on the planet and as you showed feeding on sulfur compounds, radioactive decay, and the like? Phevans can correct me if need be, but I think what he was saying was while there might be co-evolutionary competition on the racetrack of life NOW--the early environments of Earth didn't have those opportunities for munching on other creatures. Yet they evolved? How so? Nich filling. Despite all the talk about "design parameters" and the "Privileged Planet", on another angle Earth is a REALLY nasty place. Perhaps unlike Gleise, our world roils and boils and gets hit and knocked on its side and gives us the Four Seasons, massive oceans, etc. I shouldn't expect simple organisms to NOT change on worlds like that, should they be discovered. Without sounding like a tautology, those prokaryotes that filled "niches" survived and passed on their traits. Those that could not or did not either stayed where they were and became tame little boogers or died. They filled niches in a very dynamic planet's constant hoisting of drying ponds and limited light vs. increasing light and getting stuck alternately in caves and out in the open seas. No doubt some were isolated from the main group--like proto humans from the chimpanzee, and filled a niche. Those "pros" with better eyespots or melanin that served as primitive light receptors found better eating among each other, among those without eye spots, and sprouted multicellular extensions to handle the new neural load of having to process more information than their cousins who became their meals. We can call this "survival of the fittest" if we like, but really it is not akin to Spencer's use of the phrase for some remorseless method of weeding out those whom he considered socio-biologically unsound. Many have commented on this horrid abuse of Darwinian thinking. I am not an expert on unicelled creatures--but have they NOT changed? And how did they get around to these other environs? An example easy to locate about larger creatures can demonstrate. I DO know something about "dart frogs", also called poison arrow frogs. Few terrestrial creatures are more toxic than these cute little things. I follow some of the research on these little fellows as some of their toxins are being researched for use in a wide array of medicinal use, including therapy for pain. All are interrelated closely, and yet isolation on environs as dissimilar as mountain tops (similar to what has happened to some salamanders who lose limbs and colors) and limited swamp ranges turns some of them stark blue, poisonLESS, and YET STILL unafraid of human beings whereas their cousins downstream always run and hide---and are multicolored. Why? Well, those on the mountain tops and swamps have had no reason to be fearful of large creatures as they don't generally encounter them in the Sipilwani regions of Suriname. Their relatives DO. This change was forced upon them to adapt and is what forced dedrobates tincturious (the Tinc, to hobbyists) to turn into dendrobates azureus (the Blue frog), the latter of which is critically endangered and lives now mostly in captivity due to its habitat being destroyed (in this case not from man, but from shrinking isolated swamps). And so it goes. Not in "fittest" dramas per se, but in just filling a niche. Playing the devil's advocate from the Darwinian point of view, one can imagine that some prokaryotes were just more than happy basking in those "warm little ponds". Others, like the Blue Frog (the one that still bears part of the Tinc look, stares at people and never runs for its life like the devil is after it, and yet is NOT as poisonous as the others), had to adapt to rapid changes in the environment. Stephen Jay Gould once said that evolution is not a ladder, and man is not the measure of all things. He IS the unusual measure of a dynamic planet where things turn on a dime. Rather than a massive Tree of Life, we have a misshapen, "copiously branching network" of creatures that, like SOME of our prokaryote pals, never got larger. But they DID evolve. Now they free tickets to space, as you said. What Gould called (in a Scientific American article) "the morphospace" of life indicates that no one evolutionary direction is favored over another except survival. That's it. Nothing else is really obvious. Some unicells turned into multicelluar creatures that ate the other ones. Some prokaryotes found little reason to get multicelluar, and like the Horseshoe crab, have the appearance of being the same as they were eons ago but are still more evolved than if you could see them back "in the day." They just did so in a more low key way. Turn back the hand of time, he said, and you'll never get humans again. Maybe lots of arthropods--A Red Lobster Feast every square mile of dry land. One commentator said we should all go down the street and just stare at one another in utter amazement that we are even here. Others regard Gould's statement, however, as what one researcher called " a massive, hulking non-sequiter." That is to say there IS an upward movement in evolution in terms of complexity, and the human brain certainly fits the billing. You might not get humans again elsewhere letting biology's clock tick away, but certainly, should we not expect creatures with two eyes staring back at us from some nether region of deep space? Wakefield Tolbert
phevans To clear up YOUR mistake: http://en.wikipedia.org/wiki/Survival_of_the_fittest
It was used by Darwin in the 5th edition of The Origin published on 10 February 1869, in a secondary header of Chapter 4 about natural selection [2] and at several places in the text, mostly using the phrase "Natural Selection, or the Survival of the Fittest". He gave full credit to Spencer, writing "I have called this principle, by which each slight variation, if useful, is preserved, by the term natural selection, in order to mark its relation to man's power of selection. But the expression often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate, and is sometimes equally convenient." At this time the word "fittest" would have primarily meant "most suitable" or "most appropriate" rather than "in the best physical shape".
I wrote survival of the fittest not only the fittest survive. Obviously it was too much trouble for you to look up the history of the phrase. Was it too much trouble to quote me correctly too or was that just more carelessness? No real competition? Tell that to your immune system. Be quick about it because it will ultimately fail and prokaryotes will happily dine on both your carcass and your expired immune cells until there's nothing left. Name the ways we can survive that prokaryotes cannot. Good luck. Since prokaryotes inhabit our bodies, inside and out, they thus survive exactly everywhere that we do. But the point is they survive where we cannot. This newly discovered species probably takes the cake for ultimate survivalism: Newfound Bacteria Fueled by Radiation
They are the microbes from hell, or at least from hell's Zip code. A team of scientists has found bacteria living nearly two miles below ground, dining on sulfur in a world of steaming water and radioactive rock. A single cell may live a century before it gets up the energy to divide. The organisms have been there for millions of years. They will probably survive as long as the planet does, drawing energy from the stygian world around them. The microbes, found in water spilling out of a fissure in a South African gold mine in 2003, are not entirely new, the researchers report in today's issue of Science. They are similar to ones found in other extreme environments and among the most primitive life forms ever described. What is unusual is that their underground home contains no nutrients traceable to photosynthesis, the sunlight-harnessing process that fuels all life on Earth's surface. Such a community is an oddity on this planet -- and is of interest to people looking for life on other ones. "There is an organism that dominates that environment by feeding off an essentially inexhaustible source of energy -- radiation," said Tullis C. Onstott, a geoscientist at Princeton University who led the team. "The bottom line is: Water plus rocks plus radiation is enough to sustain life for millennia." The surfaces of other rocky bodies in the solar system are all too cold, too hot, too dry or too toxic to support the kind of life known on Earth. Their subterranean environments, however, are likely to be more hospitable and stable. More important, many may contain the short list of ingredients that seem to be all the South African microbes need. "This is a very nice potential model of the habitability of Mars, Jupiter's Europa and other moons," said Steven D'Hondt, an astrobiologist at the University of Rhode Island, who was not involved in the project. "The sorts of ecosystems you could get there could certainly be something like this." Onstott agreed. Mars is known to have both subsurface water and uranium. Onstott's team's findings suggest that even without volcanoes to warm the Martian environment, organisms that may have evolved in a more temperate time may survive there. "The existence of radiation may be enough to keep life going, and perhaps even thriving and evolving," he said. "I think this really increases the likelihood that we will find life beneath the surface of Mars." For more than two decades, microbiologists have been able to find and retrieve permanent colonies of bacteria living hundreds or even thousands of feet below ground. In virtually all cases, however, the subterranean environments contained carbon-based molecules from decayed plants or animals. The energy in those molecules' chemical bonds was all traceable to the sun, captured by plants through photosynthesis. The microbes from the South African mine appear to exist outside this food chain. The underground chemistry appears to go like this: First, water molecules -- H2O -- are split by radioactive particles. The result is hydrogen, oxygen and hydrogen peroxide. The latter two substances then attack the mineral pyrite (also known as iron sulfide or "fool's gold"), making sulfate through a process called oxidation. The bacteria then uses the hydrogen to turn the sulfate back to sulfide, a process known as reduction. In doing so, it captures some of the energy in the sulfate's chemical bonds, which it uses to make ATP, the molecule that is the universal coin of energy exchange in living things. Radiation then splits more water, producing more hydrogen peroxide, which turns the sulfide back to sulfate, effectively "recharging the battery." The deep underground water where the bacteria live is loaded with these nutrients. But the exceedingly torpid organisms are using only a fraction -- perhaps as little as one-billionth -- of what is available to them. They live 45 to 300 years between cell divisions; in comparison, some strains of E. coli bacteria can divide every 20 minutes under ideal conditions. "For some reason it is advantageous to grow slow rather than fast in this environment," said Lisa M. Pratt, a geologist and astrobiologist at Indiana University, who is one the authors of the Science paper. "Philosophically, that is very interesting, because on the surface it is advantageous to grow fast and use nutrients before something else does," she added. All of the microbes are members of the phylum Firmicutes . One strain dominates, and there are a few others. The dominant bacterium does not yet have a scientific name. Some of the researchers have almost finished reading its entire genome, which will allow them to figure out how closely related it is to Firmicutes found elsewhere. A study published last winter established that large phylum as unusually ancient -- it was the first branch after the common ancestor of all bacteria, which emerged about 3.5 billion years ago, according to the fossil record. A chief obstacle in research on deep-subsurface microbial communities is proving that what people find was not carried in by them, their equipment or the drilling apparatus. This team -- which included American, Taiwanese, German and South African scientists -- showed that none of the microbes they found were like ones found in surface water near the mine. They also dated the water by measuring the amount of helium in it. Helium is produced by radioactive decay, and thus is evidence of how long the water had been underground. It appears to be a mixture of water that came from the surface as recently as 3 million years ago, mingled with water already there from 2.5 billion years ago. "They did a nice job of constraining and characterizing the environment of that system," said James K. Fredrickson, a geomicrobiologist at Pacific Northwest National Laboratory in Richland, Wash., who was not on the team. The research was principally done by Li-Hung Lin, a former graduate student of Onstott's who is now on the faculty of National Taiwan University. He descended three times to the part of the tunnel where the fissure was hit to get samples. It was 1.7 miles underground, and the temperature of the rock was 125 degrees Fahrenheit.
To clear up a classic mistake, Darwinism does not say "only the fittest survive", it says "the ones that survive fill a niche". There's no overarching measure of "fitness" - prokaryotes survive in ways that we cannot, and vice versa. There's no real competition here. Phevans
Wakefield Any organisms more complex than prokaryotes, including creatures with eyes, are temporary. Prokaryotes are ostensibly the oldest and empirically the most successful organisms throughout the entire history of life on this planet. They are abundant in every niche where more complex forms eke out a living and are abundant in niches where more complex forms can't survive. They're even more abundant in orbit about the earth as there's billions or trillions of them riding up into orbit with every single astronaut. If survival of the fittest were the rule we shouldn't be here. The only materialistic survival-of-the-fittest POV reason I can think of for our existence is prokaryotes need telescopes to locate habitable new planets and spacecraft to transport them there before the earth is fried to a crisp by the sun in a few billion more years. That makes us no more than long range reproductive organs for the real rulers of this planet. DaveScot
Well now. I suppose this all depends on what is "typical" as observers in a Universe where so far the sample size is not known to be more than one kind of being. But the paper also offers: Data are the domain of facts, likelihoods are the domain of logical deduction, and the priors are the domain of theoretical prejudice. Of course. Now, let's say MY theoretical "prejudice", and what I consider the "liklihood," and "domain of logical deduction", are all part of what I call "trending"---starting from the bottom, the sun is a garden variety star; very plain-jane. A typical drab hued rose in a veritable garden of delights in the Cosmos. My prejudiced view--"typical" or not--is one where "trends" are found in, say, the search for planets like Earth and by extension eventually (in all probability) life similar to human life. SETI's Seth Shostak has taken this a step further, and backtracking to how life probably evolved on Earth demonstrates that beings very similar to ourselves probably inhabit systems no further than about 1000 light years from Earth. Light means eyes, and ease in getting food. Food means the continued need for eyes, and eyes that evolved to see better than some lobster-like creature over vast eons of time, and two of them for focus, limbs mean mobility on the terrain, etc. And so forth. 1000 light years is far out of range for cab fare, yes, but a strong, focused, multi-megawatt signal could let them know a while from now that someone was looking up at the stars. Even a ham radio operator would pull this in by accident if nothing else(for Seth's reasoning on that distance estimate, see his take on this at this article from SETI. Extrasolar planets are now known to be typical with the latest discovery of Gleise with a planet not much unlike our own. Among the planets where now there is not much distinction anymore between solar and "exosolar" (planets are not known to Sol only these days), we find a wide variety but many are known to be rocky, like our own. Star types that support life. Extrasolar planets. Planets with crusts and not gas. All are now known to be "typical", but formerly called "exotic." We've gone down the railroad tracks and have seen the buildings, the farms, the small shops, the main depot at the next town, the tractors, the grass, and even the fenceposts. The only thing missing the travelor has not yet seen but might expect to at any moment is--New People. And so it will probably go until improved spectral analyses and improved calculations of parent-star-to-planet distance measurements finds one soon in the "Goldilocks" zone. Wakefield Tolbert

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