Evolution theorists conclude from the similarities between living beings that they descended from common anchestors. This interpretation is possible but not compelling. And some findings of similarity are difficult to interpret from an evolutionary point of view.
Sometimes organs and structures of living beings do not seem to have the optimum construction. In these cases it is assumed that they degenerated (vestigialized) in time, or that because of a presumed evolutionary rebuilding no optimum solution was possible. This argumentation is not well-founded.
Some deformities that occasionally occur can be interpreted as atavism and are therefore regarded as proof of evolution. However, this interpretation can only be applied in exceptional cases, and here only when a certain evolutionary process is already presupposed. For this reason atavism is not an independent proof of evolution.
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