The continuities with which we ended the last chapter show, if there is any question, that the Civil War and emancipation did not end the monogenesis/polygenesis debate. Instead, its end came with Darwin's deployment of natural selection as a theory of both continuity (genealogy or common descent) and discontinuity (modification, adaptation, extinction, selection) – a deployment that shattered the natural history of man upon which polygenesis rested. Linné's scheme of classification, because it was founded on the assumption of fixity, makes sense only when allied with Cuvier's natural history i.e., the fixity of species within a period and place was allied with the marked differences between places on the Earth as well as the differences between the ages of the earth.

As with the ibis and the Negro, the key referent was the place of humans and human varieties within the natural order represented by the various systems of classification. ‘Nature is man writ large, and man nature writ small’ was a common ideology of the day and one could not be faulted in venturing to say that it is an ideology that we continue to share. While a rigid classification could not account for change, more imaginative classifications did allow for the possibility of variation within species. What remained was the exploration of the mechanisms that would allow for change over time and yet remain consistent with the needs of a rational system of classification.