When trying to classify species there is the group being studied, the ingroup. However there must be a point of comparison, the outgroup, that contains previously cataloged species related to the ingroup but distant enough to posses distinct traits. The ingroup & outgroup share primitive characters because they are related. The ougroup should be equally related to the ingroup if the ingroup's species are truly in the same genus. Specialized characters are shared by some or all members of the ingroup, but not by the related outgroup, are derived from the common ancestor. The outgroup has branched with its own set of characters derived from the ancestor.