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Life On Earth

  1. Mar 11, 2006 #1
    They say that all life on earth is related, now if thats a true statement then it basically means that life has independently started on earth once in 4.5 billion years. are we really that lucky to be here and if we are then what hope does that give us in our quest to find life on other planets
  2. jcsd
  3. Mar 11, 2006 #2
    Who is 'they'?
  4. Mar 11, 2006 #3
    Many articles on the web claim that all life on earth is related,many go much further than the one below i will hunt some down.


    Even the DNA of plants is similar to that of humans. We share 60% of our DNA with a banana.
    there are many i will find more

    I take it you don't go along with their opinions
    Last edited: Mar 11, 2006
  5. Mar 11, 2006 #4
    The 'they' that Plastic Photon asks about is just about every biologist, geneticist and geologist on the planet. Indeed, I know of absolutely none who contend otherwise.

    It is understood that all life on Earth is derived from a common ancestor. This, however, does not mean that life arose on Earth only once. It may simply mean that other forms of life proved less successful and were displaced by the form of life from which we are descended.

    It, therefore, has no influence on the probability of life on other planets, which has always been beset by the problem that we are trying to extrapolate from a sample size of one.
  6. Mar 12, 2006 #5
    Ophiolite thank you for your reply.

    However I have to ask, you know i do:smile:

    Is there evidence that there were other lifeforms which were less successful and therefore didn't survive.Especially when you consider they have no idea how life got its initial spark
    Last edited: Mar 12, 2006
  7. Mar 12, 2006 #6
    The first part is correct, about all life having a common ancestor, but if you’re wondering about evidence for a second genesis, I’m not so sure you’ll be able to find any. The idea is that once life got started, it would soon overwhelm all other attempts at life beginning from scratch all over again.
  8. Mar 12, 2006 #7

    what i'm trying to find out is if life was something that was inevitable and theirfore happened more than once or if it was just a matter of extreem luck and only happened once, which would then have a major bearing on the chances of us finding extra terrestrial life.

    if it was inevitable then i asume it would have started in lots of different places but if that were true it would mean all the different lifeforms which appeared must have been close to each other for one particular life form to overwelm all the others but when you consider the size of the earth that seems unlikly to me , and so it must mean life on this planet started due to nothing more than the most amazing amount of luck and therefore life in our universe could be an extreenly rare occurance.
  9. Mar 12, 2006 #8
    I think you’re thinking from one extreme to another: Either life is a very rare event, or that it shoots up very quickly all over the place like wildfire. There is an indication that like began quite soon after the Earth formed, but that doesn’t necessarily mean it began in many different places all at the same time. Perhaps a second genesis would take millions of years, by which time the life that had already established itself had occupied every available niche.
  10. Mar 13, 2006 #9
    When you mix Hydrogen with Oxygen under the right conditions you get Water H2O or other forms of Water like H2O2, under other conditions you get Ice.

    If you mix the right chemical complexes under the right conditions you would get life, It is a chemical given, Where there is Hydrogen and Carbon and under the right conditions you get Hydrocarbons or under other conditions you get Carbohydrates.

    The life Process not only required an assortment of the right Chemicals but also an assortment of conditions as well.

    Life is by chance, it was a given Chemical accident, Accidents Happen, I would say Chemistry says it's possible but it would indeed be rare Naturally, Trying to hear a Radio Wave coming to Earth that got transmitted a couple of billion years ago would be a severely weak signal and probably highly distorted if not detectable by our Amplified Radio Telescopes.

    If there is one shot for Life in every Galaxy within the Universe then don't count on ever seeing them in person for millions or Billions of years, It could be a race less advanced or maybe more advanced, Time will tell.

    Earth popped up trillions of Life forms over its existence, those are pretty good odds of Chemistry, Not one, but trillions.:bugeye:
  11. Mar 13, 2006 #10
    This is arguably one of the most important questions facing science today, and like all good questions it has no clear answer.

    I would recommend to you a book called Rare Earth, by Ward and Brownlee. They examine the likelihood of life beyond the Earth. Their conclusion is that microbial life is common in the Universe, but that intelligent life is very rare, possibly even unique.

    We have seen that life can exist in a variety of hostile environments, which a few decades ago we would have thought would have excluded life. So we now have the various extremophiles inhabiting very cold, or very hot, or very saline, or very acid environments. When Apollo astronauts recovered parts from one of the robotic Surveyor space craft from the moon, it was found that some microbes left on the craft accidentally were still viable.

    This gives us a very wide range of habitats in the Universe in which life might arise and flourish. However, for complex multi-celled organisms capable of developing intelligence to emerge and survive, appears to be a much more challenging task, with a much more restricted range of opportunities.

    One of the puzzles concerning the origin of life is how quickly it appeared on the Earth. The Heavy Bombardment Phase, that peppered the Earth and all the terrestrial planets with comets and asteroids, occured 3.9 billion years. We have clear fossil evidence from 3.6 billion years ago. So it seems that life emerged in just 300 million years.

    Now that seems like a long time, but consider this. The prokaryotes, microbial life forms without a nucleus, had the planet to themselves for one or one and a half billion years. They are often referred to as primitive, yet the difference between them and non-life is far greater than the difference between them and the eukaryotes (which include all the multi-celled plants and animals). So it appears as if this transition to life occured rapidly, in comparison with the transition to complex life. That raises questions.

    It may be that we shall discover self organising properties of organic compounds that lead inevitably to life. In that case we would expect that there may have been several forms of life which emerged at the outset, only one of which was ultimately successful. It is unlikely that we would be able to capture the signature of that life form. An alternative explantion would be that life arrived here from space on comets. This is an old idea that has enjoyed something of a resurgence of late: google for pan spermia.
  12. Mar 13, 2006 #11
    If I was to listen to my own intuition then I would say that advertizing our location on Earth is very dangerous, I would say that we need to find out the full extent to technology before attempting to talk to life on other worlds outside our own star system. Doing so could lead to the irradication of the Human species in the twinkle of an eye without the power of knowledge.:surprised

    Intuition says, only listen and keep quiet and keep the radio signal signitures from Earth as small as possible until we can advance more, Alien Technology may have also studied Stealth Technology in more advanced ways than what we have discovered, they could sneak up on the Earth and not be seen, Alien Ninjas if you will.

    Outside my intuition says, Go for it.:bugeye:
    Last edited: Mar 13, 2006
  13. Mar 13, 2006 #12


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    Yes, we can't forget that the aliens could be like us, in which case contacting them would be like the Native Americans and Africans sending "come and visit" invitations to Europe.
  14. Mar 13, 2006 #13
    Like Data Quoted on one episode of Star Trek, How would it feel being anihilated by an Alien race and never ever seeing the face of your Enemy.

    If Teleportation becomes a reality in a Highly advanced Alien race they could simply teleport the Human Race into the Vacuum of Space without even putting up a fight.

    We can learn from Science Fiction and use it to our Defence, It's like knowing all the Chess moves before a move is even made.:bugeye:
    Last edited: Mar 13, 2006
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