Throughout the last quarter of the nineteenth century, researchers became increasingly interested in explaining the ways in which mammalian teeth, especially molars, and their complex arrangements of cusps arose along both developmental and evolutionary timescales. By the 1890s, two theories garnered special prominence; the tritubercular theory and the concrescence theory. The tritubercular theory was proposed by Edward Drinker Cope in 1883, and later expanded by Henry Fairfield Osborn in 1888, while the concrescence theory was developed by Carl Röse in 1892. (...) Reviews concerning the evolution of mammalian molar teeth tended to paint the two theories as occupying opposing sides, and debates arose between their main proponents; however, their tenets do not seem logically incompatible. Throughout this paper, I argue that the conflict that arose was due not to the content of the theories, but to a diverse array of commitments Cope, Osborn, and Röse held, which turned into background assumptions within the setting of these theories. This history traces the context in which Cope, Osborn, and Röse developed the tritubercular and concrescence theories, and the ways in which the assumptions that these investigators held influenced their perceptions of their theories. (shrink)