limits of change from Re: Pasteur and nature of science

From: bivalve (
Date: Tue Jan 08 2002 - 14:47:43 EST

  • Next message: george murphy: "Re: Pasteur and nature of science"

    >I assume this may be as good as any evidence you can offer. And I don't mean to belittle in any way this work. But, taking a skeptical view of this paragraph, after all of the fusions, duplications, transfers and increases in the genetic info/complexity, fruit flies are still fruit flies. You haven't shown that the type can be pushed to change indefinitely. There always seem to be boundaries which limit the amount of change we can induce. I'd like to see an experiment where a fruit fly becomes a hornet.<

    How do you define a fruit fly? The standard definition of a fly (Order Diptera, of which fruit flies are a small part) identifies them as a group of insects that have only two wings. They have modified the hind pair of wings into a pair of small knobs, used in balance control. A few flies are wingless, including a New Zealand cousin of the fruit fly that lives on bats. However, mutant fruit flies have been produced that have four wings. By non-evolutionary definitions, it is no longer a fly, much less a fruit fly.

    At a higher level, insects (Class Hexapoda) have six legs and one pair of antennae. The number and type of appendages, especially on the head, are among the most basic features characterizing the major groups of arthropods-crustaceans, trilobites, chelicerates, myriapods, insects, etc. Yet some mutant fruit flies have eight legs and no antennae. By this feature, they are more like spiders than insects.

    Ironically, by insisting that they are just variant fruit flies, you follow an evolutionary definition of fruit fly, based on their recent descent from other fruit flies. This is similar to the classification of mammals, birds, reptiles, and amphibians as fish.

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