Posted by Carlos on August 26, 1998 at 12:52:10:
In Reply to: Do We Know? posted by GaDS on August 26, 1998 at 03:41:35:
GaDS said:
Do we know how evolution works? We have seen domestication of animals, and we have seen the development of many varieties of animals and plants based upon what has been of benefit to the human race, but I don't recall ever hearing of humans being able to create something that could be considered a new species.
Have you read The Beak of the Finch? That book discusses assisted speciation of fish, among many other topics. We had a good discussion about that book and related topics a few months ago. Below is the link to the appropriate archive page.
I don't doubt that animals can speciate to the extent that morphologically they suited to their niche in the environment. But the general idea of evolution progressing from proto-bacteria to humans seems a bit much to take. The entire idea of evolution is that those better suited to survival through genetic variation will tend to dominate in the gene pool as successive generations arise. The catch to all this is that 1) the variation must confer a significant advantage upon the individual, 2) it must be a dominant feature, 3) it must occur often enough to persist in the population, and 4) it must not be so drastic that the individual is rejected by the population. The famous example given in evolutionary biology is that of the giraffe. Those with longer necks and legs would be able to forage for food unavailable to most of the others. But how much longer would the neck and legs have to be to confer a "distinct advantage"?
Again referring to The Beak of the Finch, researchers found that very small changes in beak size conferred significant survival advantages depending on whether the Galapagos were in a wet or dry period. In a period of drought, if all of the lower vegetation has been consumed, then a height advantage of just a few inches could conceivably be enough to ensure the survival of one giraffe compared to a shorter one.
To the best of my knowledge, the average height of giraffes hasn't really changed much.
That's because we haven't been around nearly long enough to observe any change.
For more specialized adaptations, the argument is even stronger. How, for example, does a complex eye evolve through the mechanism of natural selection? The development and specialization of the various tissues, the interworkings of all the parts, and development of behavior and neural support mechanisms that allow it to function could not have happened independently. Unless ALL the parts are in place and function correctly, there is no advantage to maintaining them.
Dawkins has addressed the question of the eye in several of his books. At this site is an article he wrote summarizing his views on the evolution of the eye, and he specifically addresses your implicit question of "what use is half an eye?"
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