Life on earth has existed continuously for over 3.5 billion years. The oldest known fossils are single celled organisms. As one look in younger rocks, more complex organisms begin to appear. As the rocks get younger, the organisms contained therein resemble living organisms more and more. There are also groups of organisms which are known only from fossils. These organisms have become extinct and left no descendants. From these observations, most reasonable people conclude that evolution is a scientific fact. Organisms evolve from existing forms; organisms also become extinct either because of disasters or failure to adapt to a changing environment or because of a failure to compete.

Because organisms evolve, new characters appear. As new characters appear, most biologists want to remove organisms possessing these new characters from the old taxon by placing them in a new taxon of their own. For example, when a species within an existing genus have evolved a suite of new characters, it may be necessary to place this species in a new genus of its own. That is exactly why the genera Lampropeltis and Pituophis are recognized: they have evolved a new suite of morphological characters not found in the old genus in which their ancestor belongs. The species found within Pituophis and Lampropeltis are descended from a species of Old World Elaphe which migrated to the New World. But recognizing the genera Pituophis and Lampropeltis means that Elaphe is "paraphyletic." Paraphyletic taxa are not acceptable to the Hennigians because Hennig defines a taxon as consisting of a single ancestor and all of its descendants. Clearly, it is impossible to recognize new taxa if one must obey Hennig's absurd rule.

Let's travel back in time to 3.5 billion years ago when life first began on earth. What one will find is most likely nothing except very similar looking single celled organisms that most biologists may classify either in a single species or at best a single genus. If one sticks around long enough (give or take another half a billion or one billion years), then one is going to eventually find organisms that differ from these earliest species. Some of the new organisms may be so different that they may deserve to be classified in a new genus because of new characters (such as a nucleus and a nuclear membrane). But doing so means one has to violate Hennig's rule. That is because as soon as a species is removed from the old genus and transferred to the newly recognized genus, the old genus becomes paraphyletic. So, we must make an exception to Hennig's rule in order to recognize more than 1 genus. A taxonomist can repeat the same process with higher taxonomic ranks. Pretty soon it is obvious that the prohibition of paraphyletic taxa is not possible if one were to recognize more than a single species, a single genus, a single family, a single order, a single class, a single phylum and a single kingdom. It is clear then that in order to have a biological classification that is of any use, Hennig's rule against the recognition of paraphyletic taxa must be ignored and exceptions made to this rule for every single taxonomic rank in existence.

The cladists, who demand that we all obey Hennig's impractical rule, ignore the impracticality and in fact impossibility of its implementation. Their insistence on disqualifying paraphyletic taxa such as Elaphe and Clemmys have resulted in proposals that force them to recognize taxa that cannot be consistently defined, taxa that herpetologist J.D. Lazell called "contrived". Obeying Hennig's impractical rule by recognizing contrived taxa is thus not scientific progress. It is ideological nonsense.

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