Why do some medical sources question the vestigiality of the appendix?
The reasons for this are multiple, but they largely stem from the simple fact that most physicians are not trained in evolutionary biology. The erroneous “completely nonfunctional” definition of a vestige is primarily found in medical papers, textbooks, and dictionaries (e.g. Williams and Myers 1994, p. ix). Using this incorrect and nonevolutionary definition, it is logical to conclude that a structure is not vestigial if its function is discovered. For instance, based upon this incorrect definition, Williams and Myers 1994 incorrectly argue that an evolutionary vestige cannot be both a complex and a “regressive” structure (p. 27). Similarly, a modern version of Gray’s Anatomy confusingly implies that the appendix cannot be both vestigial and specialized (Williams and Warwick 1980). However, vestiges are very often complex or specialized structures, in fact overly complex for their functions, and prime examples are the wing of the ostrich and the eyes of blind cavefish. A vestige can b
