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Humans unique to the universe?

  1. Jan 2, 2007 #1
    Are humans unique to the universe? This is a question being asked by SETI, the Search for Extraterrestrial Intelligence.


    It has been argued that the human organism is a unique product of the universe. The conditions and criteria for the emergence of a human population are so rare and seemingly unrepeatable in the universe that humans are thought by some to be a one time affair.

    Could there be approximations that come close to a human organism elsewhere in the universe? What would be some of the predominant features of such an organism?
  2. jcsd
  3. Jan 2, 2007 #2


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    I learned a fascinating point about the probabilities involved in advanced organisms evolving on other planets on a recent Nova or Nature program. They made the point that in order to have enough *time* for more advanced organisms to evolve, the solar system with the Earth-like planet in the correct orbital range also needs to have a large planet like our Jupiter to help deflect incoming asteroids. Without a large planet in the solar system, the frequency of large environmentally-altering impacts is too high to allow enough time for advanced animals to evolve.

    I'd never heard that point before, but it seems to make sense. Anyway, to your question, I'd guess that there are a number of candidate solar systems where mammal-like organisms can evolve. Whether they make the step to self-awareness and other human-like qualities, and start broadcasting RF energy off their planet.....that's a harder question.
  4. Jan 2, 2007 #3

    D H

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    Many factors may preclude the development of intelligent life. The Drake equation implies a large number of intelligent civilizations could be present in our galaxy. The Fermi paradox asks "why haven't we seen or heard them?" The Rare Earth hypothesis (see http://en.wikipedia.org/wiki/Rare_Earth_hypothesis) answers the Fermi paradox by saying that we are more-or-less unique.
  5. Jan 2, 2007 #4


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    Be careful with preconceptions. At the moment, we have nowhere near enough information about what is going on in other solar systems to say with any conviction that the conditions on earth are either rare or unrepeatable.
    "Could" is a very general word, so the answer is an unequivocable (and utterly meaningless) yes.
    It is difficult to know, but we have good reasons to believe that they would have some features in common with us. And I don't mean hands and feet, I mean biology and chemistry.
  6. Jan 2, 2007 #5
    I think I've seen that program too. I also recall a program on Discovery about the Moon that eluded to its presence contributing to life on our planet (tides and deflecting incoming asteroids, if I remember right).
  7. Jan 2, 2007 #6


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    Oh yeah, that's right. I forgot about that point. I'm pretty sure it was in the same show. They showed some simulations that implied that the Earth would not spin stably like it does now if it didn't have the Moon. That implied no climatic stability, and therefore no reasonable expectation of advanced evolution. Thanks for reminding me of that! That was a pretty interesting show.
  8. Jan 2, 2007 #7
    You're right... I think it was the same program.
  9. Jan 2, 2007 #8
    Very good point. Recently, Jupiter deflected Shoe-Maker Levy very nicely. The point about the time we got between major catastrophies is a pertinent one as well. We've had a relative 65 million years to evolve from rodents to humans without the hinderance of carnivorous, 8 ton dinos. And the later comments about the moon inducing the tides is extremely important. It perhaps supplied the transitional environment of tidal pools where organisms evolved the capability to withstand open air along with being submerged in water. Incidently our moon is comparitively unique to its parent planet, earth, in our solar system.

    Russ Watters, I agree, we really don't have enough information about what's going on in other solar systems to make an educated quess about "intelligent life" on other planets. Its only when you tally up the conditions that have surrounded our planet and our evolution that it begins to look almost impossible that such a synergy of conditions have happened elsewhere. However, personally and statistically, I believe that if it has happend once (as in here) it will have happened elsewhere. I really wonder what the outcome, elsewhere, looks like!
  10. Jan 2, 2007 #9

    Chris Hillman

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    Exactly! This is perhaps the single most important point which could be made in discussions of this kind: we are talking about informed speculations, and not, strictly speaking, about science. History suggests in the most compelling fashion that when you haven't yet looked at what actually happens in Nature, preconceived notions are generally wrong. In this case, we have not yet examined very many biospheres, so it seems perilous indeed to attach much weight to alleged generalizations about biospheres in general.

    (Some of us feel that NASA has its priorities all upside down, at least for "the forseeable future". In my view, intensive robotic exploration of Titan is a far more reasonable thing to be planning than the insane notion of transporting humans to Mars, much less getting them back alive. Robotic exploration is far more cost effective, and thus yields far more useful data for a given amount of money spent, plus we don't run the risk of dismantling an agency like NASA entirely if voters become disillusioned after numerous tragedies involving the loss of successive crews, as seems likely, given the extreme risks involved, at least not unless the U.S. spends itself into bankruptcy, which would presumbably result in the dismantling of far more than NASA. The Moon landing was a great romantic adventure, there's no denying that, but the most important thing it accomplished, politically speaking, was producing an undeniably striking picture http://en.wikipedia.org/wiki/Blue_marble which could however have been taken just as easily, and a great deal more cheaply, by a robotic spacecraft. From a scientific standpoint, IMHO, Voyager and Pioneer were truly epochal; those accomplishments of the Moon landings which could not have been readily achieved by robot explorers, such as scooping up and returning Moon rocks, were comparatively trivial.)

    Don't misunderstand: speculation hath its place. In particular, it can help clarify how we might go about exploring a possible biosphere years before we actually start sending missions.
  11. Jan 3, 2007 #10
    Speaking of Titan, is there any chance that neucleotides can form in a methane rich environment then actually lead to a life form? Are there any experiments going on that research this possibility? I agree that the search for life elsewhere requires such an open mind that you almost just have to wait for the discovery before considering it. But, as you say, if we don't explore the possiblilities, we may not recognize the phenomenon as a life form.

    Its looking more and more as though mars has water present on its surface.


    Water has always been the "well spring" of life from the perspective of the life on this planet (which is 3/4s covered with water). But, how necessary is water to the formation of life? There are indications that viruses could well be the first form of life on earth. Do viruses need water to replicate and or mutate? Check out this article

  12. Jan 9, 2007 #11
    It would be possible to compile an approximation by way of extrapolation with regard to the probablility or possibility of there being a form of life that resembles the human form (and function)

    The method would be to compile all of the conditions that have contributed to the emergence of life and thus the evolution of humans on this planet.
    This would entail making note of
    - the distance of earth from the sun
    - the type/size/composition of sun in this solar system
    - the size and orbit of the moon compared to the earth
    - the earths orbit including its presession or "wobble"
    - the neighboring planets and their integral influence on this planet (protection from bombardment, gravitational influence or what have you)
    - the mechanisms that produced water on earth
    - the possiblity of viro-genesis on earth from extraterrestrially free floating viruses.
    - the fact that some space debris has managed to hit earth in the past
    - and ?

    If we take these kinds of conditions to be the factors that have shaped the evolution of the human-form, with all our implications as an intelligent being, and apply them as probability factors, I wonder if we'd generate a statistic of how many planets are enjoying the same conditions as this one?

    I mean if you take the probablility of the same conditions occuring in one or two locations throughout, say, 20 gallaxies (billions of suns in each) doesn't that begin to suggest that we may not be "unique" in terms of form and function?
  13. Jan 9, 2007 #12


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    You're referring to the Drake equation, which DH mentioned in post #3. Check out his wikipedia link.
  14. Jan 9, 2007 #13
    Thank you berkeman. What are the possibilities that I missed that? (100%)

    With so many galaxies to choose from (billions and billions) and many of them sporting a ring shaped habitable zone it seems as though life, complex or otherwise, can take place pretty well anywhere out there.
    Last edited: Jan 10, 2007
  15. Jan 10, 2007 #14
    There are a 100 billion or so galaxies up there? No one could possibly even imagine what type of other life forms could exist beyond our planet. Who's to say it has to be carbon based? That is all we know. A far as we know, other life might not even contain anything close to a base pair type DNA... I would take a guess though that if intelligent life is out there, it evolved in a similar fashion to us. Some form of a brain evolved from a lesser species most likely. No one knows for sure...
  16. Jan 10, 2007 #15


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    I would like to add to that. We have a statistical sample of 1 element, and worse, we couldn't even have a statistical sample with 0 elements - antropic as this argument might be, it is valid to show the essential bias in our very limited sample set, which, after removing the bias, is empty! Probabilistic arguments based upon this *trivial* observation are hence entirely speculative with no ground at all, and stuff such as the Drake equation are just a factorisation of a single speculative quantity in several speculative quantities.

    The observation that life *did* devellop on our planet, and moreover into an advanced and intelligent form is a non-observation, because every intelligent observer has to make that observation, even in a universe where the probability for this to happen is so low that it is even improbable to have happened in his universe. We cannot conclude from that fact that the devellopment of life into intelligent forms must somehow be "easy" and rather probable if the right conditions are present. Maybe it is, maybe it isn't, but the (biased) observation that it did on our planet (it had to, for us to be here to observe it) brings strictly no information in the debate.

    I object to that: the most important devellopment from the apollo missions was the devellopment of easy cooking pans, no ? :biggrin:
  17. Jan 11, 2007 #16


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    Actually I think we do have a null set.
    The definition of intelligence in this case seems to be transmission of a signal.

    We don't transmit anything (barring the one minute Arecibo transmission back in the 70's)

    That wouldn't qualify as a valid hit, based on what I know of current search algorithm, even if something was lucky enough to intercept it.

    If there is another technological civilization why do we expect them to be more forthcoming than we are?
    Seems to me you need to add another parameter to the Drake equation.
  18. Jan 12, 2007 #17
    Does life naturally evolve into a complexity that produces intelligence? It only appears to based on one example of what has emerged on earth.

    It was a bolide that wiped out over 90 percent of life on earth that actually made it possible for mammals to become the dominant form of life on the planet. Without that catastrophy, mammals would probably still consist of a variety of small rodents.

    Is it manditory that mammals be the intelligent form of life? Can viruses evolve an intelligent nervous system? Or reptiles? Are there signals that we're missing all together because they're generated by anerobic or nonaquatic life forms?

    Thinking "out of the box" might help SETI with its mission.
  19. Jan 12, 2007 #18
    I think there definitely is life out there even considering the vast coincidences that have come into play for us to evolve. Even if Earth is the only planet with intelligent life in the whole galaxy or universe perhaps. Is there ever one of anything in the universe as we observe it other than life? That's because we're not looking far enough. Infinity covers a lot of space and time. We are unique in a sense as molecules in the cell of a nucleus, the most complex piece of a comparatively larger surrounding, but we just can't see far enough to comprehend with our finite brains.

    And searching for intelligent life....not something I think has any meaning. For what, to find ways to live longer? Then what? To gain more individual knowledge? Then what? To live longer? You see, it's redundant. We're not made to live forever nor gain too much knowledge. Our universe or planet that harbors us is not something to overcome but something to live modestly in.

    I don't mean it to sound as a moral issue, which I will say, I have none nor do I have a religion, I just call it ethics. But I can't help but question my questions.
    Last edited: Jan 12, 2007
  20. Jan 31, 2007 #19
    Why do people want to survive and live longer then? Not to reproduce and pass on our genes, that cannot be what drives us because once we are unable to(too old,ect) we wish to live anyway.

    In that sense we would mate and then be useless to the human race, except to help the younger ones to mate. Is that the reason we "want" to live, after our primary genetic purpose is fulfilled?
    Do we have a underlying genetic goals that say
    o.k, next, umm,
    2) keep those guys alive long enough to do the same?
    So maybe we try to gain knowledge and information to more sucessfully reproduce and also to help the rest of the species.

    IF, thats correct then we dont have any way as aspecies to stop our need to expand and gain knowledge, it would be hereditary.
  21. Feb 3, 2007 #20

    I assume this comes with the question, how can a virus survive without it's own means of reproduction, as this assumes that no other life forms existed yet.
    So, how do viruses did that? Or is the current behaviour of viruses (using a host life form to reproduce their DNA) something they addapted to after other life forms came into existence?
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