Archaeopteryx - Archaeopteryx: Answering the Challenge of...

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Archaeopteryx : Answering the Challenge of the Fossil Record The lack of intermediates showing tooth reduction has more to do with the lack of fossils and the way evolution operates than with any lack of such intermediates in the history of the birds. The number of Jurassic and Cretaceous bird fossils number only a few dozen at best. It is not surprising that such intermediates are not represented. However, as has been pointed out previously the expectation of finding such smooth intermediates is fallacious. "Advanced" and "primitive" carry certain connotations. Biologists now use 'derived' for "advanced" and 'ancestral' for "primitive". However, what are considered derived characters for one group cannot be used to decide what are derived characters in another group. For instance, derived characters in snakes are (in order of appearence); reduction of limbs, loss of limbs and reduction from two to one lung, acquisition of fangs, acquisition of sensory pits. Thus from the point of view of snake evolution, humans, with their retention of limbs, retention of two lungs, absence of fangs and absence of sensory pits, are ancestral, or "primitive". As can be seen from this example what is sauce for the snake is certainly not sauce for the human! The absence of teeth is considered a derived character in birds , it is of little importance when deciding which characters are "advanced" in other groups . Thus the claim that, "the duck-billed platypus and the spiny anteater, mammals that do not have teeth, should be considered more advanced or highly evolved than man" is ludicrous, and Dr Gish should know this. "Evolutionists have long maintained that contemporaries could not have an ancestral-descendant relationship but if related, they must have evolved from a common ancestor sometime in the past." (p. 116) This is only true for populations , not for species in general. A population can be described as a (usually) reproductively isolated group of individuals which comprise a specific gene pool. Changes to that gene pool over time (the death of individuals, the birth of new individuals, mutations, etc.) all conspire to alter the genetic composition of the population so that the descendant population represents the original population plus the sum of the changes over time. Thus the descendant population cannot coexist with the ancestral population because the descendant population is the ancestral population, plus the sum of the changes over time. However, in the vast majority of cases, one population does not comprise the entire species. There are usually multiple populations spread out geographically, some interact, some do not.
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This note was uploaded on 11/22/2011 for the course GLY GLY1100 taught by Professor Jaymuza during the Spring '10 term at Broward College.

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Archaeopteryx - Archaeopteryx: Answering the Challenge of...

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