why are there more small animals than large animals?

Discussion in 'Earth Science' started by Raize, Jun 19, 2007.

  1. Orleander OH JOY!!!! Valued Senior Member

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    25,817
    link Well, some humans are getting smaller. Namely Americans. Are we changing our own evolutionary destiny?

    Americans no longer tallest people in world

    LINCOLN, Neb. (U-WIRE) - It's official: Americans are no longer the tallest people on Earth. That honor now goes to Europeans, including the Dutch, Norwegians, Danish and Germans.

    According to the Annals of Human Biology, Europe has overtaken the United States in the height department, a distinction the Americans had for the last 200 years.

    In the United States, the current average height of an adult man is 5 feet, 9 inches, and for an adult woman, it is 5 feet, 3 inches, according to the Centers for Disease Control and Prevention.

    In the Netherlands, though, men average 6 feet tall while the average woman is 5 feet, 7 inches, according to the Leiden University Medical Centre in the Netherlands.

    Though there are many reasons for the disparity in height, the Annals of Human Biology suggest the shift in growth trends might have something to do with the amount of junk food Americans consume in comparison to Europeans.

    Jennifer Snyder, a marketing specialist at the University Health Center at the University of Nebraska-Lincoln, agreed that the eating habits of Americans could have some effect on growth patterns.

    "We (Americans) eat a lot more preservatives and additives (than Europeans), and the food is processed differently here," Snyder said.

    Another reason why Americans are on average shorter than Europeans could be the result of more pollution in the air, Snyder said.

    Although Americans as a whole are getting shorter, some are looking for ways to combat shortness.

    In 2003, the Food and Drug Administration approved the use of synthetic growth hormone for youth with idiopathic short stature, or shortness for no apparent medical reason.

    The treatment consists of an injection every day for many years, but the procedure is expensive, not usually covered by insurance companies and sometimes yields disappointing results - the average increase in height is about two inches.

    While being extremely short can be a hindrance in everyday life, not everyone who uses growth hormones does so out of necessity. Many patients who opt to take a growth hormone choose to undergo the therapy for cosmetic reasons.

    "For some people, taking it is more of a self-esteem issue," Snyder
     
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  3. It has to do with predator-prey relations. You have to have a support system, on which the bio-sphere can sustain itself. As the larger predators expand in numbers, the prey begins to dwindle, and then the larger cannot sustain on the given resources.
     
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  5. Raize Registered Member

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    Thermodynamics


    Predator-prey relations

    Longer generation times
    - law of allocation
    - slower rate of adaptation

    Larger animals require larger habitats and more resources
    - Any given amout of land will support more small animals than large
     
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  7. Fraggle Rocker Staff Member

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    This is just the Melting Pot at work, isn't it? Until a few decades ago, America's gene pool came primarily from those tall countries: England, Scotland, Ireland, France, Germany, Holland, and Scandinavia. Now we're having a wave of immigration from places where people aren't especially tall, like Latin America, and from places where they're downright short, like East Asia. It isn't just height, look at what's happening to clothing sizes: The big department stores have to carry ladies' dresses in Size 2.

    We aren't getting shorter. Short people are coming to live with us so their children can be taller.

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  8. Orleander OH JOY!!!! Valued Senior Member

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    I thought since America is getting fatter, they were eating more but not better. You need vitamins and healthy food to grow.
    I never considered immigration.

    Are people from island countries smaller because they have a smaller environment?
     
  9. iceaura Valued Senior Member

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    24,091
    That has recently been shown to not explain the trend.

    I'll try to find a link, but a few people have done some exhaustive data mining and concluded that Americans really are getting a bit shorter, and even more dramatically not getting taller as Europeans are.

    After all the immigration and ethnicity and whatever has been allowed for

    (America is not the only country with lots of short first generation immigrants, and first generation is all that matters - by the second and third generations, after allowing for income status pretty much every ethnic group is the same average height in any given country)

    Europeans are now taller than Americans, in general, and the gap is widening.

    The strongest correlation is with income inequality. Countries with large inequality of income have shorter citizens.

    Another, smaller, correlation is with junk food.

    edit in: http://en.wikipedia.org/wiki/John_Komlos A start for the intrigued, with literature citations.

    http://www.newyorker.com/archive/2004/04/05/040405fa_fact Expository article
     
    Last edited: Jul 14, 2007

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