New Reading in our Week 1 Folder

In extra reading on January 22, 2010 by ariew

If you are hankering for extra reading and mathematically laden papers aren’t your idea of a good time (i.e. the piece by H. Allen Orr), I’ve got the things for you!

I put in a paper by Gayon which outlines (very briefly) some main differences between Darwin’s theory of natural selection and modern conceptions.  As you will likely discover by next class meeting on Tuesday, I think Gayon doesn’t say enough about how natural selection changes from a Newtonian force-based account to a probabilistic account.  But, better than most Gayon at least recognizes that one of the main differences for modern evolutionary biology is the rejection of Darwin’s central condition of a struggle for existence due to overpopulation.  While Gayon recognizes it he underplays its importance to understanding how modern natural selection is different than Darwin’s.  For Darwin, the struggle for existence due to overpopulation is the key cause of evolution.  Modern biologists (ever since R.A. Fisher) have recognized that not all dense populations undergo anything like the intense competition that Darwin believes to be the case.  Modern biologists have replaced the struggle for existence condition for natural selection with a distinct concept, “fitness”–a term which Darwin rarely uses except to invoke (starting in the 5th edition–I think) the slogan “survival of the fittest” which is, quite literally, meaningless.  Intrigued?


One Response to “New Reading in our Week 1 Folder”

  1. I haven’t finished the Gayon piece yet, but here’s some preliminary thoughts about the force of selection.

    The discussion of the distinction between artificial and natural selection in the Dawkin thread spurred the following thought about what the “force” of selection might be.

    In artificial selection, the intentions of the selectors exert a physical force onto individuals. Individuals that do not have the desired traits are forcefully removed whereas those who do are kept to mate. The “force of selection” here is not a metaphor, there really is a transfer of energy going on when individuals are removed.

    In unintentional human selection, e.g., the hypothetical man-induced selection of dogs with shorter flight ranges due to the construction of waste dumps, there is no visible force taking creatures away or keeping some from mating. Instead, those who do have more offspring are able to do so because of their adaptive traits (yes, I’m assuming adaptationism is correct here and not taking into account random drift, recombination, etc.). Here “selection force” seems to be metaphorical.

    Natural selection is similar to unintentional human selection. There again is no Being actively preventing mating and killing unfit individuals.

    Understood as such, the difference between the latter two and the first provides a serious challenge to the analogy Darwin can draw between natural and artificial selection: they are not forces of the same type!

    However, I think that Darwin regard them as the same type of forces.

    Below is a possible interpretation of Darwin’s analogy between nature and men:

    A human hand taking away foals that can’t jump is one that exerts an active force against this undesired trait.

    An low wall separating a population of horses and the only water hole is an environmental factor that selects against the same trait.

    From the individual’s point of view, being taken away and being blocked from water amounts to the same effect-they do not survive. Thus, the “force” originating from human intention has the same effect of certain configurations of the environment. An environmental factor that causes the individuals with adaptive traits to survive and proliferate stands in the same relation to these individuals as an intentional action. Thus the environmental factor exerts the same sort of physical force. Thus artificial selection and natural selection are now the same sort of process.

    However, understood this way, the “force” of selection is not the clash of population overgrowth with the cap, it is a real physical force.

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