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Author Topic:   The astronomical impact on terrestrial evolution
Briterican
Member (Idle past 3948 days)
Posts: 340
Joined: 05-29-2008


Message 1 of 15 (540866)
12-29-2009 3:43 PM


I'd be curious to hear what you guys have to say about the types and degree of impact (forgive the pun) that astronomical processes have had on terrestrial evolution.
Let's get two big ones which I know a little about out of the way first:
  • 1.Impact:
    Comets and meteors have pummeled the Earth and other surviving bodies in the solar system throughout its history. The evidence for this is overwhelming and some of it is quite literally under our feet. This would have been far more dramatic in the early stages of the formation of our solar system, when the number of bodies was greater and so then was the chance of impact. An equilibrium (of sorts) has been reached at the stage we now find ourselves, in which collisions are less common but still quite frequent in terms of the smaller meteorites that come down regularly.
    There is overwhelming evidence that collisions have caused mass extinction events on the Earth. These would dramatically alter the potential course of evolution, resetting the parameters for survival and ending any hopes of it for a great many in one violent second.
    Additionally, the very nature of this violent early stage may have prohibited early life from getting a foothold:
    Paul Davies writes:
    If Earth was pounded as fiercly as astronomers believe, and if surface organisms really were well-established by 3.8 billion years ago, then life must have burgeoned almost as soon as the effects of the last sterilizing impact were over.
    Citing a study by Kevin Maher and David Stevenson from Caltech, the author goes on to discuss the possibility that life may have arisen in between cataclysmic periods only to get repeatedly wiped out:
    Paul Davies writes:
    "It is a curious thought that if life did form anew several times, then humans would not be descendants of the first living thing. Rather, we would be the products of the first life forms that just managed to survive the last big impact in this extended stop-go series."
    Davies eventually gets around this whole conundrum by presenting evidence that the earliest life forms may have been subterranean and capable of withstanding enormous heat and conditions that we would class as extremely hostile. Their closest cousins may be mirrored in the hyperthermophiles that we find today.
  • 2.Possible extraterrestrial origins of life:
    The idea here is that life arose on some body other than the Earth and was deposited here via impact. This idea most often involves comets, and it has been shown that comets contain a great deal of organic material. It was confirmed earlier this year that the amino acid glycine was found in NASA's Stardust mission to Comet Wild 2 in 2004. Found: first amino acid on a comet | New Scientist
    This is a fascinating area in its own right, but it really simply redefines the location of origin of the earliest life, and not the subsequent terrestrial evolution which I am discussing in the post.
    The next two are where I definitely hope to hear what you guys think:
  • 3.The Moon:
    What effects has our moon had on evolution? There is an unmistakable connection between the moon and living things due to its gravitational pull (tidal patterns, menstrual cycles).
    In what other ways has the moon influenced natural selection on Earth?
    The reflected sunlight from the moon that comes and goes over the course of a month has undoubtedly played a role in various ecosystems, even if just by virtue of providing better light by which to hunt and/or gather.
    The moon has undoubtedly played a large role in the cultures of human beings. I find it fascinating to think that it might actually have given us a head-start towards rationality in the sense that it provides a nearby reminder of order in the heavens, one that stands in stark contrast to the sun, and the two of which together provide an even greater insight to just what the hell is going on. What might it be like to evolve on a planet that had no moon? Or three moons? Would a three moon system have led to a more rapid understanding of physical laws, mathematics, astronomy?
  • 4. Earth's tilted axis
    What influence have the seasons on earth, thanks to its tilted axis, had on terrestrial evolution? Would it have been more advantageous to have had no tilt? Or, did this fact play a crucial role in evolution by driving adaptive features?
  • 5. What else?
    What other aspects of our astronomical history have impacted the course of evolution on Earth, and what might life be like if conditions had been otherwise?
    (--- Science: human origins and evolution forum? That would be more accurate than big bang/cosmology, please ---)
    Edited by Briterican, : Title change, note to admin re desired forum.

  • Replies to this message:
     Message 3 by Iblis, posted 01-01-2010 7:54 PM Briterican has replied

      
    Briterican
    Member (Idle past 3948 days)
    Posts: 340
    Joined: 05-29-2008


    Message 4 of 15 (541281)
    01-02-2010 7:54 AM
    Reply to: Message 3 by Iblis
    01-01-2010 7:54 PM


    How important are the seasons, and the moon?
    Thanks for your reply Iblis.
    Doesn't seem to be much interest in the thread, but then it isn't really a debate topic or one that carries any controversy.
    Your point about nebulae is fascinating and I must admit I was not aware of this aspect.
    The thing that I wish someone would address is the impact of the moon, and the seasons, on evolution. I've been trying to find information on the net about this but have come up short. There must be some major connections between the seasons (via the tilt of Earth's rotational axis) and evolution. I would guess that seasonal changes have caused organisms to adapt to the changing conditions, and possibly even to develop cyclical patterns that run in conjunction with the seasons. There's bound to be examples of this in nature.
    I also wish I understood more about the connection of the moon to biology on the Earth. Menstrual cycles are just one example of a direct connection between the moon and biology on the Earth, and I am curious if any research has shown how the moon's tidal pull may have impacted the evolution of these cycles in Earthbound creatures.
    Chances are the thread will die a quiet death hehe, but if anyone can point me in the right direction for further information on these connections I'd be grateful.

    This message is a reply to:
     Message 3 by Iblis, posted 01-01-2010 7:54 PM Iblis has replied

    Replies to this message:
     Message 5 by Iblis, posted 01-02-2010 12:05 PM Briterican has replied
     Message 6 by slevesque, posted 01-02-2010 1:50 PM Briterican has replied

      
    Briterican
    Member (Idle past 3948 days)
    Posts: 340
    Joined: 05-29-2008


    Message 8 of 15 (541340)
    01-02-2010 4:15 PM
    Reply to: Message 5 by Iblis
    01-02-2010 12:05 PM


    Re: How important are the seasons, and the moon?
    Regarding the PAH world hypothesis, there seems here some amazing possibilities. I found this detail (from wiki) particularly amazing:
    In this self ordering stack, the separation between rings is 0.34 nm. This is the same separation found in RNA and DNA. Smaller molecules will naturally attach themselves to the PAH rings. However PAH rings, while forming, tend to swivel around on one another, which will tend to dislodge attached compounds that would collide with those attached to those above and below. Therefore it encourages preferential attachment of flat molecules such as pyrimidine and purine bases. These bases are similarly amphiphilic and so also tend to line up in similar stacks. This ends up making an effective scaffold for a nucleic acid backbone to form along the bases.
    A small change in acidity would then allow the bases to break off from the original stack of PAHs and so form molecules like RNA.
    I've seen the scaffolding idea mentioned before, but I've never heard of such a close fit as the 0.34nm mentioned above.
    The wikipedia page mentions that this is untested. I hope that, if any such testing is feasible, someone is working on it.
    Iblis writes:
    I regret to inform you that some of your ideas about tides may be based on myth.
    Now that you mention it, it seems like someone told me this before. I must not have been paying attention, but I am now. Feeling a bit silly about that now hehe, but hey... you've helped me shed another misconception so, that's good.
    Iblis writes:
    This implies that the cycles are derived only secondarily from the moon, specifically its light; and that their primary cause is due to longterm species hunting and eating behavior. Modern chimpanzees do not hunt.
    Yeah, I read the primate link and I see what you mean.
    Just for grins... check out this crazy quote from a website on menstruation
    *****Warning: the following is BS******
    Human beings are affected by the moon. Women especially are affected by the moon and their menstrual cycle is intimately linked to this celestial body.
    The moon:
    * regulates your menstrual cycle,
    * can trigger ovulation and fertile times,
    * affects your emotions and
    * affects the way people behave and view the world.
    Women are connected to the moon by our blood, our hormones and our souls.
    The first step in claiming the gifts of our menstrual cycle is to become re-acqainted with Mother Moon. Putting aside all the scientific phenomena of the way the Moon affects the earths tides, weather, animals, fluids and moods, symbolically the Moon has a lot to teach us.
    I think I can safely eliminate that site as a source of reliable information.
    I have instead found several sources confirming what you've said, such as this to-the-point quote from The Straight Dope:
    Cecil Adams writes:
    The smart money says it's coincidence.
    Thanks again for the replies.

    This message is a reply to:
     Message 5 by Iblis, posted 01-02-2010 12:05 PM Iblis has replied

    Replies to this message:
     Message 12 by Iblis, posted 01-02-2010 6:38 PM Briterican has not replied

      
    Briterican
    Member (Idle past 3948 days)
    Posts: 340
    Joined: 05-29-2008


    (1)
    Message 10 of 15 (541343)
    01-02-2010 4:46 PM
    Reply to: Message 6 by slevesque
    01-02-2010 1:50 PM


    Re: How important are the seasons, and the moon?
    Hi slavesque
    slavesque writes:
    Aren't lunar tides supposed to have helped the mixing of the primordial soup to help abiogenesis ? I think I remember my astrophysics teacher saying something like that. Although it's not a clear memory at all so I may be wrong.
    Here's a quote from wiki on the "radioactive beach hypothesis":
    Zachary Adam at the University of Washington, Seattle, claims that stronger tidal processes from a much closer moon may have concentrated grains of uranium and other radioactive elements at the high water mark on primordial beaches where they may have been responsible for generating life's building blocks.[39] According to computer models reported in Astrobiology,[40] a deposit of such radioactive materials could show the same self-sustaining nuclear reaction as that found in the Oklo uranium ore seam in Gabon. Such radioactive beach sand provides sufficient energy to generate organic molecules, such as amino acids and sugars from acetonitrile in water. Radioactive monazite also releases soluble phosphate into regions between sand-grains, making it biologically "accessible". Thus amino acids, sugars and soluble phosphates can all be simultaneously produced, according to Adam. Radioactive actinides, then in greater concentrations, could have formed part of organo-metallic complexes. These complexes could have been important early catalysts to living processes.
    There seems to be plenty of notions about how life got its start, but they obviously can't all be right. I hope to live long enough to be here for a breakthrough in this field.
    Also, while reading your OP I did find that the ''overwhelming evidence fore multiple collisions that caused mass extinctions'' was a bit of elephant hurling, since the most supported one (dinosaur extinction) is still a pretty controversial theory in the scientific community. Never mind all the others. I couldn't say that any have overwhelming evidence..
    I probably use the term "overwhelming evidence" a bit too much. I'll watch that.
    However, given the iridium layer at the KT boundary, it seems that any controversy regarding the dinosaurs' extinction seems to be more about which impact(s) were responsible rather than were impact(s) responsible.
    Here's a quote from Richard Cowen of the University of California, in a paper titled "The KT Extinction":
    An asteroid big enough to scatter the estimated amount of iridium in the worldwide spike at the K-T boundary may have been about 10 km (6 miles) across. Computer models suggest that if such an asteroid collided with Earth, it would pass through the atmosphere and ocean almost as if they were not there and blast a crater in the crust about 100 km across. The iridium and the smallest pieces of debris would be spread worldwide by the impact blast as the asteroid vaporized into a fireball.
    It is an old paper (1999), but I'm not convinced that there is any ongoing controversy about the iridium layer. In other words I'm pretty sure that it is attributed to an impact as described above, and it just happens that before it are dinosaurs. After it, no dinosaurs.
    Thanks for the reply.

    This message is a reply to:
     Message 6 by slevesque, posted 01-02-2010 1:50 PM slevesque has not replied

    Replies to this message:
     Message 13 by RAZD, posted 01-02-2010 7:02 PM Briterican has seen this message but not replied
     Message 14 by Minnemooseus, posted 01-02-2010 8:53 PM Briterican has seen this message but not replied

      
    Briterican
    Member (Idle past 3948 days)
    Posts: 340
    Joined: 05-29-2008


    Message 11 of 15 (541344)
    01-02-2010 4:50 PM
    Reply to: Message 9 by slevesque
    01-02-2010 4:25 PM


    Re: The Big Smack
    slavesque writes:
    Now, in the case of the dinosaur extinction is one of the few (if not the only one) who could be said to have ''overwhelming evidence', although it would be quite an exageration in my opinion. We could discuss this particular case in this thread if Briterican doesn't mind.
    I'd be delighted, and again, Iprobably have used the term "overwhelming" a bit haphazardly.

    This message is a reply to:
     Message 9 by slevesque, posted 01-02-2010 4:25 PM slevesque has not replied

      
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