A monodimensional understanding of both the past and the present has often characterized the historical background provided for scientific disciplines. It scans the past for the antecedents of the current cutting edge. But establishing such genealogical connections is difficult, even on the level of terminology. For example, neither “animal” nor “consciousness” has ever been defined without contention. The main current (and past) problem with the term “animal” is taxonomic: does it include people or not? and if so, are people included in only their physical aspect or in some more encompassing sense? An examination of 18th and 19th-century taxonomical treatments of the great apes shows how convictions and uncertainties on these issues were expressed through classification. With regard to “consciousness” the main problem has been whether that term refers to something shared by humans and other species. An examination of 19th-century attempts to claim that non-primates like the dog resembled humans more closely than did apes shows that this issue too reflects scientific as well as lay discomfort at the awkward proximity of other primates. A final problem with establishing scientific genealogies is that they often assume past consensus among experts on issues where there was actually intense disagreement, complicated by the difficulty of deciding who the experts actually were two or three centuries ago. None of these problems has completely disappeared even now.