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Author Topic:   Nested Hierarchies
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Message 1 of 1 (80)
01-13-2001 3:48 PM

One of the most convincing lines of evidence for macroevolution or common descent is the existence of multiple nested hierarchies.
What is a nested hierarchy?
Due to the hypothesis of common descent, the predicted pattern of organisms at any given point in time can be described as "groups within groups."
This nested hierarchical organization of species is in contrast to the continuum of "the great chain of being" and the continuum predicted by Lamarck’s theory of organic progression.
Few other natural processes would predict a hierarchical nested classification. Real world examples that cannot be classified as such are elementary particles (which are described by quantum chromodynamics or QCD), the elements (whose organization is described by quantum mechanics and illustrated by the periodic table), the planets in our Solar System, books in a library, or specially designed objects like buildings, furniture, cars, etc. That organisms merely can be related to each other is not enough
to support macroevolution; the nested classification pattern that satisfies the macroevolutionary process is very specific. It is interesting to note that human languages, which have common ancestors and are derived by descent with modification, generally can be classified in nested hierarchies.
So, as in another recent discussion, cars don't really fit into a nested hierarchal pattern. They form more of a network. An air conditioner in a Buick is about the same as in a Lamborghini as far as how it is built.
Biological populations, in contrast, have different genes that produce similar results.
For example the body plans of many sharks and dolphins are remarkably similar. Yet, dophins and sharks have very different genomes that produce such similar results. In the automobile example it is as if two completely different designs of air conditioners were used for the Buick and the Lamborghini.
Typically, the nested hierarchies are referenced as twin nested hierarchies because the morphological/anatomy based nested hierarchy is one and a molecular level/genetic nested hierarchy is another. This is, however, slightly inaccurate because there are actually multiple nested hierarchies based on the morphological similarities being comparedon different features, or based on the genetic similarities being based on comparing different genes.
Not only do these "multiple" nested hierarchies exist, but the different nested hierarchies largely match each other. So, when we do attempt to check the traditional morphological characteristics against the genetic make-up of a species, we get very, very similar results.
This fits macroevolution very well as the lack of such a pattern or a pattern that diverged from the morphological classification systems would have destroyed theories concerning biological evolution. And macroevolution specifically predicts that such patterns should match each other.
Are there any other interpretations of this pattern out there?
Note: One possible objection to this is that nested hierarchies don't exactly match. As you might notice I never make such a claim, but all of the exceptions I'm aware of are largely accounted for by gene flow or other known mechanism.

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