Announcement

Collapse
No announcement yet.

Moderate compelxity less expensive than tought

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Moderate compelxity less expensive than tought

    http://www.sciencedaily.com/releases...le+Feedfetcher

    ScienceDaily (Sep. 28, 2010) — The more complex a plant or animal, the more difficulty it should have adapting to changes in the environment. That's been a maxim of evolutionary theory since biologist Ronald Fisher put forth the idea in 1930.

    But if that tenet is true, how do you explain all the well-adapted, complex organisms -- from orchids to bower birds to humans -- in this world?

    This "cost of complexity" conundrum puzzles biologists and offers ammunition to proponents of intelligent design, who hold that such intricacy could arise only through the efforts of a divine designer, not through natural selection.

    A new analysis by Jianzhi "George" Zhang and coworkers at the University of Michigan and Taiwan's National Health Research Institutes reveals flaws in the models from which the cost of complexity idea arose and shows that complexity can, indeed, develop through evolutionary processes. In fact, a moderate amount of complexity best equips organisms to adapt to environmental change, the research suggests. The findings will be published online in the Proceedings of the National Academy of Sciences.

    The study focused on a genetic phenomenon called pleiotropy, in which a single gene affects more than one trait. Examples of pleiotropy are well known in certain human diseases, and the effect also has been documented in experimental animals such as fruit flies. Biologists also recognize its importance in development, aging and many evolutionary processes. However, pleiotropy is difficult to measure, and its general patterns are poorly understood, said Zhang, a professor of ecology and evolutionary biology.

    Even so, scientists have developed mathematical models of the phenomenon, based on certain assumptions, and have made predictions from the results of the models. Zhang and coworkers decided to test the assumptions against real-life observations by analyzing several large databases that catalog the effects of specific genetic mutations on traits in model organisms (yeast, roundworms and mice). Each data set included hundreds to thousands of genes and tens to hundreds of traits.

    For simplicity, mathematical models of pleiotropy have assumed that all genes in an organism affect all of its traits to some extent. But Zhang's group found that most genes affect only a small number of traits, while relatively few genes affect large numbers of traits.

    What's more, they found a "modular" pattern of organization, with genes and traits grouped into sets. Genes in a particular set affect a particular group of traits, but not traits in other groups.

    In addition, the researchers learned that the more traits a gene affects, the stronger its effect on each trait.

    All of these findings challenge the assumptions underlying the classic mathematical models that suggest complexity is prohibitively costly.

    When Fisher first wrote about the cost of complexity, he argued that random mutations -- which, along with natural selection, drive evolution -- are more likely to benefit simple organisms than complex organisms.

    "Think of a hammer and a microscope," Zhang said. "One is complex, one is simple. If you change the length of an arbitrary component of the system by an inch, for example, you're more likely to break the microscope than the hammer."

    In a paper published in 2000, evolutionary geneticist H. Allen Orr of Rochester came up with additional reasons for the cost of complexity. According to his model, even if a mutation benefits a complex organism, it's unlikely to spread throughout the whole population and become "fixed." And even if it does that, the advantage of the mutation is likely to be small.

    By incorporating a more realistic representation of pleiotropy, Zhang's analysis found the reverse of Orr's arguments to be true. Although Fisher's observation still holds, reversing Orr's assertions minimizes its impact, thus reducing the cost of complexity.

    Further, the analysis showed that the ability of organisms to adapt is highest at intermediate levels of complexity. "This means a simple organism is not best, and a very complex organism is not best; some intermediate level of complexity is best in terms of the adaptation rate," Zhang said.

    The new findings help buffer evolutionary biology against the criticisms of intelligent design proponents, Zhang said. "The evolution of complexity is one thing that they often target. Admittedly, there were some theoretical difficulties in explaining the evolution of complexity because of the notion of the cost of complexity, but with our findings these difficulties are now removed."

    Zhang's coauthors on the paper are former U-M graduate student Zhi Wang, now at Sage Bionetworks in Seattle, Wash., and Ben-Yang Liao of the National Health Research Institutes in Taiwan.

    Funding was provided by the U.S. National Institutes of Health and the Taiwan National Health Research Institutes.
    Last edited by Heraclitus; September 30, 2010, 15:42.
    Modern man calls walking more quickly in the same direction down the same road “change.”
    The world, in the last three hundred years, has not changed except in that sense.
    The simple suggestion of a true change scandalizes and terrifies modern man. -Nicolás Gómez Dávila

  • #2
    You could've fixed the title.
    "The issue is there are still many people out there that use religion as a crutch for bigotry and hate. Like Ben."
    Ben Kenobi: "That means I'm doing something right. "

    Comment


    • #3
      Fixing a title is a moderately complex task?
      "Just puttin on the foil" - Jeff Hanson

      “In a democracy, I realize you don’t need to talk to the top leader to know how the country feels. When I go to a dictatorship, I only have to talk to one person and that’s the dictator, because he speaks for all the people.” - Jimmy Carter

      Comment


      • #4
        Originally posted by Asher View Post
        You could've fixed the title.
        How? On the old forum it was possible to fix the thread title by editing the OP title in the first few minutes.
        Modern man calls walking more quickly in the same direction down the same road “change.”
        The world, in the last three hundred years, has not changed except in that sense.
        The simple suggestion of a true change scandalizes and terrifies modern man. -Nicolás Gómez Dávila

        Comment


        • #5
          Here too. Need to go to Edit (Advanced)
          "The issue is there are still many people out there that use religion as a crutch for bigotry and hate. Like Ben."
          Ben Kenobi: "That means I'm doing something right. "

          Comment


          • #6
            See.. the forum has evolved to be more complex

            Comment


            • #7
              Originally posted by Asher View Post
              Here too. Need to go to Edit (Advanced)
              Thanks.



              Now is anyone interested in discussing the OP and its implications?
              Modern man calls walking more quickly in the same direction down the same road “change.”
              The world, in the last three hundred years, has not changed except in that sense.
              The simple suggestion of a true change scandalizes and terrifies modern man. -Nicolás Gómez Dávila

              Comment


              • #8
                Nope. You can go now.
                “As a lifelong member of the Columbia Business School community, I adhere to the principles of truth, integrity, and respect. I will not lie, cheat, steal, or tolerate those who do.”
                "Capitalism ho!"

                Comment


                • #9
                  Thread can now be closed. It is not tittied correctly.
                  "The issue is there are still many people out there that use religion as a crutch for bigotry and hate. Like Ben."
                  Ben Kenobi: "That means I'm doing something right. "

                  Comment


                  • #10
                    Can a mod edit that last post? I meant titled. Thanks.
                    "The issue is there are still many people out there that use religion as a crutch for bigotry and hate. Like Ben."
                    Ben Kenobi: "That means I'm doing something right. "

                    Comment


                    • #11
                      I'll take the Penis Mightier....
                      "Just puttin on the foil" - Jeff Hanson

                      “In a democracy, I realize you don’t need to talk to the top leader to know how the country feels. When I go to a dictatorship, I only have to talk to one person and that’s the dictator, because he speaks for all the people.” - Jimmy Carter

                      Comment


                      • #12
                        Is Asher turning straight on us?
                        Indifference is Bliss

                        Comment


                        • #13
                          Whats more important is 13".

                          Comment


                          • #14
                            Originally posted by Asher View Post
                            It is not tittied correctly.


                            Thread is now properly tittied.
                            Libraries are state sanctioned, so they're technically engaged in privateering. - Felch
                            I thought we're trying to have a serious discussion? It says serious in the thread title!- Al. B. Sure

                            Comment


                            • #15
                              Originally posted by Thoth View Post


                              Thread is now properly tittied.
                              Moderate complexity in organisms
                              Modern man calls walking more quickly in the same direction down the same road “change.”
                              The world, in the last three hundred years, has not changed except in that sense.
                              The simple suggestion of a true change scandalizes and terrifies modern man. -Nicolás Gómez Dávila

                              Comment

                              Working...
                              X