In certain important respects, Darwin and Wallace's (1858) revolutionary concept of 'natural means of selection', its elaboration in Darwin's theory, and its application to man at once confirmed and required a sea change in the concept of species, in ideas about man's place in nature, and in explanations for human differences. Yet however novel Darwinism looked in Britain (though not in France), rupture is an insufficient metaphor for this intellectual transformation since its logic was also historically embedded in contemporary discourses. Moreover, Darwinian speculations on the origins of human diversity — dysteleology notwithstanding — recall in part certain earlier monogenist strategies to combat polygenist assaults on their doctrine by compromising with the racialization of anthropology. Wallace and Darwin both endeavoured to reconcile the premise of a unitary human origin with the seeming reality of 'those striking and constant peculiarities which mark the great divisions of mankind' by hypothesizing that 'the races of man diverged at an extremely remote epoch from their common progenitor' and thenceforth evolved differentially during the immensely long process of speciation.^[142] Wallace's proposition that human races originated through the ancient operation of natural selection on the physical structure of a 'single homogeneous' primitive race (with the power of natural selection afterwards confined to man's 'mental and moral' character) is analogous to Lacépède's projection of the organic differentiation of very divergent races to a long-distant past when the impact of climate on the single original human species was much greater. So too, Serres's concept of 'three primordial types' had served tacitly to rationalize the premise of original unity with the alleged facts of actual racial difference and inequality.^[143]

Wallace's conjectural history of human racial evolution culminates in a utopian scenario in which the 'inevitable extinction' and displacement of the 'lower and more degraded races' would produce a world 'again inhabited by a single homogeneous race, no individual of which will be inferior to the noblest specimens of existing humanity'. Darwin similarly anticipated a 'not very distant' future in which 'man in a more civilised state, as we may hope, than the Caucasian' would be separated from the remaining apes by a 'break' wider than the present one 'between the negro or Australian and the gorilla'. In his textbook on anthropology, Topinard evidently agreed. These evolutionist prognoses of a bleak future for all 'lower' — non-white — races resemble more the polygenist Hombron's prediction of the obliteration of 'inferior races and species' than they do Serres's more optimistic forecast of the restoration of human unity through racial 'fusion'.^[144] Yet elsewhere, Topinard proposed a variation on Serres's theme, envisaging 'plurality of races in the past and unity in the future' as a necessary outcome of endless crossings and extinctions. Theoretical future unity, however, would be limited by the 'influence of the milieus', an 'adjuvant cause' without effect on 'ancient, fixed types' but which would come into its own as a modifying force on 'types decomposing through crossings', thereby ensuring the persistence of diversity and the continued hybrid existence of otherwise extinct types.^[145]

Recent scholarship has shown how 'extinction discourse' or 'doomed race theory' with respect to newly colonized dark-skinned autochthones developed from the late Enlightenment as a corollary of readings of Spanish colonial history, recent experience in North America and Oceania, and confidence in the necessity of progress. For most of two centuries, belief in the inevitable demise of 'inferior races' in the face of civilization served as an umbrella discourse transcending ideological differences within imperialism, notably between anthropologists, philanthropists, settlers, and administrators.^[146] Humanitarian credence in the scenario and the tension thus engendered between philanthropic and scientific imperatives are patent in a paper 'On the Extinction of Human Races' read by Prichard (1840:168-70) to the British Association late in 1839. Deploring 'the extermination of the native tribes' with the onset of European colonization, he called on 'Christian nations' to make a serious effort to prevent 'these calamities'; yet he took racial 'destruction' for granted as the inevitable outcome of encounters between 'simple' tribes and 'the more civilized agricultural nations' — 'this seems to have been the case from the time when the first shepherd fell by the hand of the first tiller of the soil'. Accordingly, he focused 'philosophical' concern on the need for what would later be called salvage ethnography, 'to obtain much more extensive information than we now possess of their physical and moral characters'.

In contrast to Prichard, John Lort Stokes (1812-1885), a shipmate of Darwin on HMS Beagle and its commander during the latter part of that vessel's Australian survey voyage of 1837-43, challenged the widely-held opinion that an 'all-powerful law', confirmed by 'history', necessitated 'the depopulation of the countries we colonize'; he took serious issue with the humanitarian rationalization of 'extinction' as a 'mysterious dispensation of Providence' that left no part for philanthropy but 'to smooth, as it were, the pillow of an expiring people'; and he called for acknowledgement of 'moral responsibility on the part of the whites'. Yet, even though he had celebrated the 'sharp', 'intelligent', 'fine-looking' appearance of the half-caste offspring of Tasmanian women with foreign men that he had met in the Bass Strait Islands, Stokes too pronounced a specific elegy for the handful of Tasmanians still surviving on Flinders Island: 'Their destiny is accomplished'; 'all we can do is to soothe their declining years, to provide that they shall advance gently, surrounded by all the comforts of civilization, and by all the consolations of religion, to their inevitable doom; and to draw a great lesson from their melancholy history'.^[147]