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Thread: marsupials

  1. #1 marsupials 
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    what evolutionary advantage is there from being a marsupial?


    "There is a kind of lazy pleasure in useless and out-of-the-way erudition." -Jorge Luis Borges
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  3. #2  
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    bigger brain - smarter

    Really this is about the only evolutionary advantage humans have over almost any organism (animal at least)


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  4. #3 Re: marsupials 
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    Quote Originally Posted by Chemboy
    what evolutionary advantage is there from being a marsupial?
    For what? Compared to what? A monotreme? a placental?..a non mammal? Advantage or disadvantage needs context.

    Is it really that difficult to write a complete sentence with a well formulated question?
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  5. #4  
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    Quote Originally Posted by Robbie
    bigger brain - smarter

    Really this is about the only evolutionary advantage humans have over almost any organism (animal at least)
    Sounds like you think humans are marsupials...
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    Quote Originally Posted by Megabrain
    Quote Originally Posted by Robbie
    bigger brain - smarter

    Really this is about the only evolutionary advantage humans have over almost any organism (animal at least)
    Sounds like you think humans are marsupials...
    That was also my first reaction. The question, however, is vague and uses the word 'from'. ...thus my response. 'From' what? compared to what?
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    The more I read it the more it does my head in...

    What evolutionary advantages do marsupials have over other animals, might be better?

    If that's it, well they are not so vulnerable when giving birth (or carrying), since a lot of them are bipedal they may not be so good at climbing (4 feet are far more stable, even humans use all four limbs to climb).

    BUt I'm not into zoology so that could all be crap.
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  8. #7 Re: marsupials 
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    Quote Originally Posted by Chemboy
    what evolutionary advantage is there from being a marsupial?
    to rephrase...

    Why did marsupials evolve? What mutation or whatever originally occured to give rise to them because of their greater chance of reproducing?
    "There is a kind of lazy pleasure in useless and out-of-the-way erudition." -Jorge Luis Borges
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  9. #8 Re: marsupials 
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    Quote Originally Posted by Chemboy
    Quote Originally Posted by Chemboy
    what evolutionary advantage is there from being a marsupial?
    to rephrase...

    Why did marsupials evolve? What mutation or whatever originally occured to give rise to them because of their greater chance of reproducing?
    This has been a debate in biological evolution of mammals for some time. There is no one answer. The principal difference is the length of gestation...nearly all marsupials have shorter gestation periods than their placental counterparts. Marsupials come in many forms..similar to carnivores...rodents...or have similar body morphs in their fossil record.

    The question can be rephrased to one of what advantage or disadvantage is there to a female internally carrying its potential offspring for a longer or shorter period of time. In general placental mammals are 'branier' than marsupials or monotremes. Placentals have larger and more developed parts of the brain that we associate with decision making. It's thought that the longer an offspring develops within the mother, the better chance of this brain having time to develop. There is not a one-to-one relation between length of gestation and brain size but there is a definite trend or pattern. 99.999 % of organisms in Nature do not develop the brain capacity of a placental mammal so it is not much of an advantage or need in most ecological niches. Big brains take a lot of time and energy to produce and a lot of time and energy to maintain.
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  10. #9 Re: marsupials 
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    [quote="Jellyologist"]
    Quote Originally Posted by Chemboy
    The principal difference is the length of gestation...nearly all marsupials have shorter gestation periods than their placental counterparts. .......
    Placentals have larger and more developed parts of the brain that we associate with decision making. It's thought that the longer an offspring develops within the mother, the better chance of this brain having time to develop.
    However, note with interest that the humans have a twenty one month gestation period - it is just that twelve months of it is spent outside the mother. It is during that period that most of the massive brain growth that makes us human occurs.
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    They can attain pretty high speeds from hopping right? Speed always seems to be advantageous. I don't think they can manipulate objects with their hands the same way we can though, or sweat as well.
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  12. #11 Re: marsupials 
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    [quote="Ophiolite"]
    Quote Originally Posted by Jellyologist
    Quote Originally Posted by Chemboy
    The principal difference is the length of gestation...nearly all marsupials have shorter gestation periods than their placental counterparts. .......
    Placentals have larger and more developed parts of the brain that we associate with decision making. It's thought that the longer an offspring develops within the mother, the better chance of this brain having time to develop.
    However, note with interest that the humans have a twenty one month gestation period - it is just that twelve months of it is spent outside the mother. It is during that period that most of the massive brain growth that makes us human occurs.
    That's true. We need to remember, however, that humans are just one of hundreds of placental mammalian species. We are an extreme in mammal evolution and not represenative of most mammals today or even that of the primate fossil record. Mammals are and have been mostly small creatures squirrel size and smaller. The pet hamster is more representative of a mammal 'norm' than a human or giraffe.

    With humans it's thought that our heads have achieved maximum size for development within the mother and still allow for childbirth. Then, as you point out, brains continue to develop after birth.
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  13. #12
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    Someone refresh my memory: Where did marsupials evolve? And where do we find them today? Haven't they been largely replaced by placental mammals, except in Australia, where placental's didn't arrive before humans brought them there?

    My point is, when comparing marsupials with other mammals, the obvious question would be about their 'disadvantage', not a 'advantage'. Jellyologist has tried to answer that question.

    The original question, though, was "what is their evolutionary advantage", or what gave them a "greater chance of reproducing", what was the decisive mutation (if any) that gave rise to the marsupials? That implies comparison between marsupials and their immediate evolutionary ancestors (whatever they were), not between marsupials and placental mammals.
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  14. #13  
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    Quote Originally Posted by tyciol
    They can attain pretty high speeds from hopping right? Speed always seems to be advantageous. I don't think they can manipulate objects with their hands the same way we can though, or sweat as well.
    They don't all hop. You're thinking of kangaroos and wallabies and such, which are marsupials. Also included in the hopping marsupials are pademelons. I love that name. Dextrous hands and lack of sweat don't really concern what makes marsupials marsupials (the pouch, or more specifically, the larger portion of embryonic development outside the womb...). Thanks for the input though.

    Quote Originally Posted by M
    The original question, though, was "what is their evolutionary advantage", or what gave them a "greater chance of reproducing", what was the decisive mutation (if any) that gave rise to the marsupials? That implies comparison between marsupials and their immediate evolutionary ancestors (whatever they were), not between marsupials and placental mammals.
    yeah, i'm looking more for the specific 'how's of how they evolved... the steps involved in giving rise to the marsupials we have today, with pouches.
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  15. #14 Re: M 
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    Quote Originally Posted by M
    Someone refresh my memory: Where did marsupials evolve? And where do we find them today? Haven't they been largely replaced by placental mammals, except in Australia, where placental's didn't arrive before humans brought them there?

    My point is, when comparing marsupials with other mammals, the obvious question would be about their 'disadvantage', not a 'advantage'. Jellyologist has tried to answer that question.

    The original question, though, was "what is their evolutionary advantage", or what gave them a "greater chance of reproducing", what was the decisive mutation (if any) that gave rise to the marsupials? That implies comparison between marsupials and their immediate evolutionary ancestors (whatever they were), not between marsupials and placental mammals.
    Marsupials still are abundant also in the Americas. And indeed you are quite right that you should compare them with the ancestors of mammals and not with placental mammals.

    The big answer is probably: mammals! They provide a ready made rich liquid nourishment for their young from glands. The only thing the mother needs to do is to be well fed. The mammary glands take care of the rest. It is truly a wonderful invention!
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    http://www.txtwriter.com/backgrounde.../EVpage14.html

    the article above (there are also much more substantial explanations of marsupial evolution but this has a nice pic with it and is short)

    the basis of how they came to be appears to be convergent evolution with mammals described in the article,
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  17. #16  
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    Welcome to the forum eutheria. Nice, useful first post.
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    thanks, no worries Ophiolite, marsupials are a pretty interesting bunch of critters,
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