Darwin's theory of evolutionary descent with modification rests in part on the notion that there is heritable continuity affected by transmission between ancestor and descendant. It is precisely this continuity that allows one to trace hylogenetic histories between fossil taxa of various ages and recent taxa. Darwin was clear that were an analyst to attempt such tracings, then the anatomical characters of choice are those least influenced by natural selection, or what are today referred to as adaptively neutral traits. The transmission of these traits is influenced solely by such...