If life on earth came from a single point of origin – does this indicate life elsewhere in the universe is highly unlikely?

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Discussion by: btilly
If life
on earth came from a single point of origin – does this indicate life elsewhere
in the universe is highly unlikely?
  

If all
known life on earth has one common ancestor, (Theobald calculates that a
universal common ancestor is at least 102,860 times more probable than having
multiple ancestors), does this suggest that there was one instance where
chemicals in the ‘primordial soup’ ‘sparked into life’, and since that
instance, there is no evidence to suggest that another event of the same nature
has occurred since to start a new lineage of descendents?

 

If this is
the case, wouldn’t it suggest that in the 4 billion or so years that the
conditions on earth have been right to support life, and the occurrence of life
emerging from chemicals only happened once, along with the fact that, as yet,
science has been unable to replicate the stages taken by nature to go from
primordial soup to a recognizable form of life, to single cell life, (no one
has yet synthesized a “protocell” using basic components which would
have the necessary properties of life), isn’t the genesis of life on earth a
freakishly rare occurrence?

 

Surely life
isn’t going to be commonplace throughout the universe either, especially when
you consider that the conditions on earth have been right for well over a
quarter of the 13.75 billion year age of the universe.

 

If Drakes
Equation is to be used, where fl = fraction of those planets where life
actually evolves, surely this number would have to be incredibly small. One in
a million? 0.0001%? If the rest of the equation is left as Drake’s
recommendations, the number of communicating civilizations in the Milky Way
galaxy is likely to be 0.002 – realistically 0.

 

Isn’t this
the reason scientists searching for extra-intelligent are asking – ‘Where is
everyone?” and the reason we haven’t found any evidence for life existing or
having ever existed in our neighboring planets and moons?

 


CITATIONS

Theobald,
D. L. 2010. A formal test of the theory of universal common ancestry. Nature
465(May 13): 219-223.

doi:10.1038/nature09014

30 COMMENTS

  1. No, it doesn’t indicate that other such events did not occur, just that they weren’t all successful.  That they weren’t simultaneous enough to form mergers, and that the first population to flourish blocked any further such events.

  2. But surely the fact that life sparked into life so early in early in Earths history suggests that it isn’t so unlikely? I mean if it happened at intervals of 100,000 years, it would still be very likely to happen, but would we have evidence of whatever the spark is/was?

  3. This is how I would interpret it too. It makes me wonder too how much evidence of that very early period is actually left today. I wouldn’t be surprised if we end up in a situation of having a few models of how it could have happened, but not knowing which one represents our reality.

    I’m not a biologist so I don’t know what degree this might be the case, but the question interests me: might there have been a few different replicators that ended up competing and perhaps interacting. Maybe absorbing structures from each other. I guess once we are well down the path and have RNA and then DNA the answer is no, but perhaps in these replicators infancy… We tend to read that there may have been multiple replicators and one out competed the others, but maybe they interacted in a way that was more complex…

  4. Maybe your definition of protocell is different than what is used by those who do make them in the lab.

    https://www.youtube.com/watch?…
    https://www.youtube.com/watch?…

    Also, what Greyman said. I would add to that as life precludes a new genesis, once it occurs it must spread like fire to prevent it from occurring elsewhere on the planet. Before life occurred there was a lot of RNA that spread all over, and before that there was a lot of AEG, microspheres, amino acids, etc. As soon as a new configuration occurs, it has a fertile ground to spread. I think of it as a critical-mass shift.

    I’m not too into the Drake equation. The Rare Earth Theory suggests the galactic habitable zone is the outer perimeter (where we are) meaning whatever the likelihood of civilizations is, they will be on the outer rim and thus very far apart.

    http://en.wikipedia.org/wiki/R

    The reason we haven’t found life is because we’ve barely looked, whether it’s there or not. If we turned on SETI for 5 minutes, we aren’t going to find anything. 50 years of scanning is not much of an improvement, as far as odds go. We have barely analyzed other bodies. We haven’t done anything with Europa, and Mars we’ve barely touched. Even if we did have a less than utterly pathetic sample size, our technology is simply not advanced enough to detect life, short of it producing rainforests. We’ve barely even begun the search, and we still get surprised at how much water we find.

    So why haven’t they said hi? If life is rare, they might not see us. If life is plentiful, we might not be interesting.

  5. The first life form may have gone extinct and have been replaced by other forms that came into existence as a result of evolution by natural selection. But it could also be that these first life forms still exist, on the bottom of an ocean near a hot vent or something. It seems to me that there is no law of physics that forbids the first life form from springing into existence again. Such a new “first form” would quickly be killed of by its more successful already existing offspring or it would continue to live at the bottom of an ocean near a hot vent. I am totally ignoring the fact that the chemical environment may have changed drastically since the first life form came into existence for the first time.

  6. Most biologists think the reason life only started once on Earth is because, once life exists, it consumes for its own ends the sorts of chemicals which a second abiogenesis would require, so the many intermediate steps to form a protocell from scratch never get to happen again. 

    In fact, insofar as we can comment on how widespread life should be in the universe, it seems likely to be quite widespread. Life began quite quickly on Earth. Most estimates say Earth was about 700 million years old at the time, which may sound like it took ages, but that’s also the time when Earth’s atmosphere cooled enough for its water vapour to condense, so it could rain and become an ocean. That suggests life actually didn’t take long to form at all. 

    There are as many as 10 other places in our Solar System which conceivably could have or could have had life (I forget the full list), and there are many billions of trillions of stars in the Hubble zone alone. Adding in inflationary cosmology, the number of opportunities goes up many orders of magnitude.

    The more we learn about the chemistry likely involved in abiogenesis and how it relates to the chemistry of the early Earth and the rest of space, the easier the origin of life on Earth looks. Could we be literally the only place among an enormous number of planets where it managed to happen? Perhaps. But even the most radical “rare Earth” hypothesis doesn’t think Earth is all that weird in its properties.

  7. It seems life got started relatively quickly in the favorable conditions of early Earth – conditions such as the chemical content, water content, tectonic activity, location in the Goldilock Zone, having our axial tilt, a stabilizing moon that also caused tides, etc.

    There have also been solar activity, comet impacts, plus global and local extinctions that greatly affected the life evolving here, and offered many unique conditions for evolution to explore.

    There may be lots of planets with fungal, bacterial or cellular life at various stages, but the chance of other life forms, able to communicate & located close enough to Earth during our recent interstellar awareness, is vanishingly unlikely.

    That’s why it’s so important that humanity try much harder not to trash our pale blue dot, since it might be the only paradise we can ever contact or access.

  8. If we accept that life was not created and was a product of the upheaval of the early earth then given the size of the universe and the fact that all planets form in similar ways , then it’s fair to say that this mixture for life could be hit upon again. We may never find life because of the distance habitable friendly planets are from us. My intuition is that life will only be discovered if it’s intelligent and in search of us as we are in search of it. Something like the movie ‘Contact’ with Jodie Foster.

  9.  Richard Fortey speculated (I think in his brilliant Life – An Unauthorised Biography) that during the period of heavy bombardment, early in the life of the Earth, surface-dwelling organisms may have been completely eradicated – perhaps several times over. If that is the case, then the very fact that there is life on the surface of Earth now would indicate a repeat pattern of biogenesis. However, it is equally probable that rather than the Earth being thoroughly sterilized during such early impact events, only the surface was cleansed of life. Perhaps chemolithoautotrophic hyperthermophiles (spelling?) re-colonized the surface multiple times?

    Another point regarding SETI: we only seem to take account of the spatial dimensions when considering the possibility of intelligent ETs, and tend to disregard the temporal. Is 14(ish) billion years sufficient time for us to have missed a “near” neighbour which has developed an advanced level of technology, flourished, then become extinct? Judging by the apparent pace of our own ‘race towards oblivion’, my guess is that this is entirely possible.

  10. The basic work on abiogenesis is presented by Dr. Jack Szostak.

    This has been CONFIRMED in Dr. Jack Szostak’s LAB. 2009 Nobel Laurette in medicine for his work on telomerase.

    To read the full desciption for this video go to: – http://www.youtube.com/watch?v

    There is a basic video here which also challenges creationist strawman claims. –
    http://dotsub.com/view/720518f

    The main problem with the Drake Equation is that all the inputs to the calculations are re speculative.

    There are huge variables, not only because of our limited understanding of the origins of life, but because of the “Rare Earth” hypothesis. – http://en.wikipedia.org/wiki/R

    The rare earth hypothesis is the contrary of the widely accepted principle of mediocrity (also called the Copernican principle), advocated by Carl Sagan and Frank Drake, among others.[1]

    The principle of mediocrity concludes that the Earth is a typical rocky planet in a typical planetary system, located in a non-exceptional region of a common barred-spiral galaxy. Hence it is probable that the universe teems with complex life.

    Ward and Brownlee argue to the contrary: planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the Solar System, and our region of the Milky Way are very rare.

    By concluding that complex life is uncommon, the Rare Earth hypothesis is a possible solution to the Fermi paradox: “If extraterrestrial aliens are common, why aren’t they obvious?

  11. The OP is very simplistic and ignores much of the known science of early life.

     @OP:disqus  If all known life on earth has one common ancestor, (Theobald calculates that a universal common ancestor is at least 102,860 times more probable than having multiple ancestors), does this suggest that there was one instance where chemicals in the ‘primordial soup’ ‘sparked into life’, and since that
    instance, there is no evidence to suggest that another event of the same nature has occurred since to start a new lineage of descendents?

     

    The fact that all Earth life is descended from LUCA ( http://en.wikipedia.org/wiki/L… ) in no-way explains the possible variations in the earlier RNA World stages of pre-DNA life. – http://www.dailygalaxy.com/my_

    Phylogenetic-tree  from LUCA to present time (see image) – http://upload.wikimedia.org/wi

    @OP:twitter  If this is the case, wouldn’t it suggest that in the 4 billion or so years that the conditions on earth have been right to support life, and the occurrence of life emerging from chemicals only happened once,

    This suggestion does not follow.  Even today there is bacterial exchange genetic material horizontally (without sex), so particularly before immune systems evolved, there is no reason to believe a multitude of reactions could not take place.  Competition, natural selection, and predation would look like the reasons for the reduction to one species, with all others going extinct (or becoming incorporated into the successful ones.) 

    Even these ancestral ones are now extinct!  They would probably be eaten by more competitive modern species if they appeared today.
    The present day oxygen atmosphere, actively destroyed the earlier ecosystems.

    along with the fact that, as yet, science has been unable to replicate the stages taken by nature to go from primordial soup to a recognizable form of life, to single cell life, (no one has yet synthesized a “protocell” using basic components which would have the necessary properties of life), isn’t the genesis of life on earth a freakishly rare occurrence? 

    No-one has carried through the whole process, but various parts of it have been demonstrated separately in laboratories.  

    Even if it is quite rare,  we still don’t know!  When multiplied by planetary, galactic, geological, and cosmological time scales, even rare events become statistically probable.

  12. Many people seem to think that life suddenly appeared out of the primordial soup. I don’t think this is the case at all. Proteins and the likes merged in to more complex chemistry that had the property of reproduction (RNA) which gradually increased in complexity and gained more lifelike properties as time went by. At least that is what I think. It would be hard to point at a specific moment and call that the start of life. 

  13. If we look at the chemical building blocks of life we see elements that very easily bond to other elements to create complex molecules. Helium, (of course if the most famous example), doesn’t bond practically to anything. Hydrogen, carbon, nitrogen, and oxygen are not only abundant but bond to allot. Based on this knowledge, if life evolved on Earth more than once, the conditions would have been rather similar, therefor making the life forms rather similar. Evidence for this is, of course, lacking, but if we appeal to reality of the same adaptations appearing in groups of organisms radically different from each other, across extraordinary lengths of geologic time, (see: digitigrade locomotion; saber teeth; the eye), we could project this notion to similar chemical life evolving multiple times in the deep past.

    The above assertion is paper thin, but just accept it for that. As for the drake equation… let’s just jump to end – it is not testable. Others have come along and attempted to amend it, (“At Last How Many Civilizations are There? http://phys.org/news/2012-12-a… ), but we have to remember that it is simply not testable. But based on how easily some chemicals bond, like those mentioned above, and the frequency of those chemicals in the universe, most of the big players in exo-biology, planetary-geology, astronomy, etc, would be surprised to discovered life not composed of said chemicals. (Neil DeGrasse-Tyson and others, like Lawrence Krauss have spoken on this subject many times).

  14. Joss Gibbons has it.

    On the old site I described the primordial soup as being at its yummiest just as it is about to yield runaway replicating. The replicators gobble up the “nearly there” fragments, depleting their concentrations to below abiogenesis thresholds.

    Prokaryotes (without a nucleus) look a doddle now, but eukaryotes (the cells of multicelled organisms) look to have a real thermodynamic barrier to overcome with their evolution by co-opting of other organism DNA in mitochondria and plastids. The guessed process is of absorption of one simple organism by another and a symbiotic coexistence until the absorbed organism can dump most of its now redundant DNA which would have created an interim energy deficiency for “the team” which would confer very little team advantage. (Symbiont mitochondria would have initially had a hundred times the amount of genetic material to support with energy intake before it mostly evolved out of existence. Energy requirements track gene count). It is much more arguable that the eukaryotic step only happened once because it was very very unlikely.

  15. I don’t think it’s an indicator of anything at all. It’s possible that the ‘single point’ origin of life on a planet is a rare occurrence, rather than the occurrence of life itself. Or that a system will naturally evolve towards that state, because reliable replication is such a difficult barrier, if it happens at all, it will take over everything relatively quickly at the expense of everything else. 

    The point is, we won’t know until we have a sample of more than one. And creating proto-life in a lab, basically speeding up hundreds of millions of years of evolution, seems unrealistic, but demonstrating various steps of the process is at least achievable. Then we can conjecture whether there are other reliable ways of generating complex lifeforms or even simple cellular or viral life. 

    As for not being able to communicate with other worlds, it’s pretty trivial. The technological barrier is immense. We’ve basically just started ourselves, our space technology is only a few decades old. And given what we know, the distances, the uncomfortable nature of space exploration, the vast amount of energy and time required to just get to the next solar system, and also our technological myopia, being radio-waves, which limits our horizon to only a few light-years.

    All in all, we’re just too ignorant to answer these questions. But based on what we know about life, what makes it possible, it is a reasonable assumption to expect life exists elsewhere, and in sparse pockets of abundance. All we know is that it occurred on an ordinary rocky planet, composed of ordinary stuff, orbiting an ordinary star, in an ordinary corner of an ordinary galaxy. And by the way, it can all be snuffed out just as quickly and easily.

  16.  I am enthralled by how much we have learned in the last few decades.  Many of the gaps that existed when I was a student have since been joined up.  

    Still, the unknown parts leave two divergent possibilities – life is commonplace, life is rare.  We still don’t know enough to dismiss either.   And even if commonplace, is it also commonplace to evolve into something with curiosity like ours?   Until we find out more,  we’ll probably cling to the possibility we find most personally satisfactory.   I know some who like to think we are so rare that we’ll never encounter anything we’d recognize as intelligence “out there”.   And others who think life is just what atoms do, given long enough, and that discovering some other life is just a matter of time, and looking.

    So why haven’t we found them by now?   Maybe they don’t want us to.

  17. OHooligan - 
    So why haven’t we found them by now?   Maybe they don’t want us to.

    Even if other life exists, intelligent life is much less of a possibility than simple cells.

    .. .. .. .. Then there are the distances involved.  We cannot even visually image the exoplanets of nearby stars in our own galactic spiral arm, let alone detect life in other galaxies!

  18.  Then there are the distances involved.  We cannot even visually image the exoplanets of nearby stars in our own galactic spiral arm, let alone detect life in other galaxies!

    Also, there’s the speed of light issue.  Evidence of our civilization—in the form of radio waves—has only had time to crawl a few light-decades away from the sun.

  19. i think focussing on the single ancestor too much is misleading. i don’t believe there was ever a sudden moment of creation of life. molecules self replicate into crystals and what we call life is an extension of that process. the particular selection of amino acids that we share represent the most successful plan. having one ancestor does not mean that ancestor didn’t have billions of identical copies, each of which could have been the ancestor but wasn’t just as you have billions of distant uncles who could have been your ancestor but weren’t.

    the encestor that was successful however, went on to use up all the nutrients on the planet, and continues to do so in many forms but there may be other forms of precursors to life on earth that but for our ancestor would be rife for replication and evolution.

    the unlikely events come along later. multi-cellular life for one. life probably existed for billions of years without resorting to symbiotic cells but once they did, and an advantage was gained, the arms race picked up pace and animals with nervous systems soone emerged.

    with human apes though we are dealing with small probibilities. it’s not just intelligence. intelligence exists in many animals with no evolutionary pressure to out-compete on braininess but apes have intelligence, social structure and the ability to carry and manipulate objects. by pure luck, thanks to environmental factors of the time, one subscpecies managed to develop technology.

    i for one would be surprised if there’s not any life elsewhere in the solar system, never mind throughout the universe. of course unless we find something that we call life the question will remain long after my 9 lives. life we can exchange ideas with however, I agree is most unlikely to exist in any place close enough to ever have any impact

    intelligence, and an ability to transmit communications over distance is rare, and along with the fact that the more complex an organism is, the more susceptable to environmental pressure it will be, limiting the time the species will exist.

    for a modern (and entertaining) take on how to interpret Drakes equation, i sugest you read Civilized Life in the Universe by George Basalla

  20.  

    intelligent life is much less of a possibility than simple cells.

    That’s one conjecture, yes.   The other is that we are a commonplace example of the kind of thing that atoms do.  Given enough time, who knows what kind of complex gene-vehicles might evolve.  As I said, we don’t yet know enough to pick rare vs commonplace, so will lean towards our personal preference.  Mine is for commonplace, but I know that’s just because it pleases me, not because there’s more evidence for it.

    As for meeting up, even if they aren’t deliberately hiding, yes, it doesn’t seem all that likely any time soon, given the distances and the cosmic speed limit, which shows no signs of being revoked despite all the wishful thinking of nearly a century of imaginative fiction.

  21. OHooligan

     intelligent life is much less of a possibility than simple cells.

    That’s one conjecture, yes.  

    Not really!   It is a projection from the one example we know on Earth.  Simple and single cells have been around for about 3½ billion years. Multicellular Eukaryotic life for about ½ a billion.
    It therefore appears that a much longer period of favourable conditions is required for complex life to arise, and even more time for intelligent complex life. That brings a planet’s / moon’s thermal and climatic stability + its duration, into the time-frame.

    The other is that we are a commonplace example of the kind of thing that atoms do.  Given enough time, who knows what kind of complex gene-vehicles might evolve.

    Even if that is so, there are the issues of the duration of planets, stability of orbits, climatic conditions, and the local availability of elements.
    We do not know about these for much of the universe, but we do know many orbital positions are almost too cold for chemical reactions to take place, others are extremely hot, exposed to fierce radiation, or with extreme temperature variations.

    The “Rare Earth hypothesis” explains the unusual long-term regulatory features, of our very geologically active, binary planet, in its stable orbit.

  22. I should think that the fact of there being life somewhere else in an expanding and infinite universe has a mathematical probability approaching 100%. Our ability to recognize it, however, would probably be the inverse of that.

  23. I believe that ‘life coming from a single point of origin’ on earth doesn’t make it unique in the universe. Although there is no evidence so far that there is life in other planets, I truly believe that it is highly probable that somewhere in this huge universe there are other beings making themselves the same question. The point is, that the requirements for having life on a planet are so many (e.g. having a ‘not too big’ star, not being too close and not to far from the star (habitable zone), having a moon (not too big, not too small), liquid water, having a big neighbour planet, etc.)

    Having these requirements in mind, but also the immensity of the universe, it is still quite probable that intelligent life does exist elsewhere in our beautiful universe.

  24. Have you ever heard of panspermia? According to this hypothesis, life traveled through space in meoteorites and comets, from, planet to planet. But it is unlikely based off of experiments demonstrating that organic molecules could form under the right conditions. But still it doesn’t rule out ET.

  25. Panspermia is as good a hypothesis as any, it seems to me.  Either life on earth started on earth, or it started elsewhere.   And if it started here – or could have started here – it could start elsewhere too.

    The Goldilocks notion seems to get taken too far:  must have liquid water all the time,  must have a big moon to cause tides, must have an axial tilt sufficient to cause seasons, must have a gas giant like Jupiter absorbing most of the asteroid/comet bombardment, etc…..   Yes, that’s nice, and set the scene for the way life has evolved here, but none of it is essential for the basic chemistry, is it?  

    But something else, somewhere else, might be appalled at our trifling surface gravity, or the amount of UV radiation that fails to reach the surface, or the total lack of a second or third sun in our sky, or the lack of the scorch-and-freeze cycle enjoyed by returning comets, or the easy availability of fissionable elements like Uranium.   Or might simply regard our Goldilocks Zone as far too hot – or too cold – for the reactions they depend on.

    All speculation, which can be entertaining in the hands of a talented author.   But for the Serious Stuff of mapping out what might be the Reality of our Universe, we still don’t know enough.  

    When I was at school, it was impossible to detect planets of other stars, and the conventional wisdom held that planetary systems like ours were likely to be extremely rare.   Now they’re commonplace, and we’ve detected how many?  (854 planets according to Wikipedia)   And those are just the nearby stars, the ones that a near-future expedition (500 years or so) might be able to reach without breaking any of the known laws of physics.

    So now the galaxy is teeming with planets, and with carbon and the other elements that combine to make the self-replicating things we call “alive”, there’s an energy gradient around every star, so every single one has its Goldilocks Zones for each and every taste.   And lots of planets have a North.

    You need to be very pernickity to whittle down the Suitable Places to just one.

  26. Organic
    Have you ever heard of panspermia? According to this hypothesis, life traveled through space in meoteorites and comets, from, planet to planet. But it is unlikely based off of experiments demonstrating that organic molecules could form under the right conditions. But still it doesn’t rule out ET.

    There are many places in the universe where organic chemicals have been identified, but other places in the Solar System look less favourable for abiogenesis and evolution than Earth.

    As meteorites from the Moon & Mars have been thrown into space by impacts causing crater ejecta, and have been found on Earth,  if there is other life in the Solar System, it should be able to move from planet to planet.  We should also be able to find it on other planets or moons.

    Some organisms CAN survive exposed in space for a while, and some spores can survive for  many years.

    There was an earlier discussion about some of these here:- 

    Tardigrades: Water bears in space – http://old.richarddawkins.net/
      http://news.bbcimg.co.uk/media…  There is also an article here: – http://www.nowpublic.com/stran… There is a Wiki article explaining Tardigrades resistance to extremes – http://en.wikipedia.org /wiki/Tardigrade

  27. The Rubik Cube Analogy

    For life to get started on any planet, you need an arrangement of molecules (like the ATGC of Earth DNA) which is capable of splitting, so that each half will randomly join to an opposite, resulting in two of the original. That’s common knowledge, but the following thought experiment IS NOT: Take the Rubik Cube as a statistical (and geometric) analogy for the liklihood of any specific arrangement of molecules in space. Then, imagine each colored square representing A,T,G, or C on the molecule. Shrink one mole of these imaginary Rubik Cubes down to the size of water molecules. This volume would be about the size of a glass of water, by the way. Question: How many random Rubik Cubes in this volume will be “perfectly solved” purely by accident? Your intuition is probably zero, but the correct answer is about 500! So what? Well, it means for a planet even as small as this volume, there would be 500 “attempts” at creating life that would SUCCEED, every single second! Because a different 500 “successes” would happen the next second. The most successful patterns of molecules end up dominating, and eating up the rest as raw materials, just like in Conway’s Game of Life. I wish Dawkins would start using this analogy, but he may not have heard of it, yet, and I think he currently believes life to be astronomically rare. The thing is “astronomically improbable” is not a problem at all when you consider there are 6.02×10^23, building blocks in even a glass of water (i.e. a mole of molecules). It seems 100% certain to me that even a planet the size of a basketball, if containing a sufficiently number of different compounds (like merely 4!) would end up with some pattern of molecules in it resembling fish (at a minmum) probably in hundreds (not even millions) of years, after the first replication event.

  28. BTW, the question of why don’t we notice any other life in the universe is fairly simple, to me. Light travels extremely slow. Only going around the earth 7 times in one second is practically frozen and stationary in cosmic terms. We’ve only been broadcasting electromagnetic waves for about 60 years from this planet, but it will be another 100,000 years before any of that light gets outside even our little speck of a galaxy. Assuming ours to be an ‘average’ galaxy that would mean other galaxies are also just now beginning to transmit signals, because other galaxies have had the same amount of ‘time’ (since the big bang) to evolve life as we have. But don’t worry, things should start “picking up” soon.

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