In a single chapter, it is only possible to scratch the surface of the complex intersections whereby a novel meaning of race was normalized across a wide spectrum of western Europe discourses, as holistic, 'environmentalist' Enlightenment explanations for human variety and change lost ground to the differentiating physicalist agenda of biological determinism and taxonomy. I focus on the overlapping, recurrent tensions between ideas of human unity and diversity and between monogeny and polygeny, culminating in their partial resolution by evolutionist theory. These mobile, ambiguous relationships and the ideological conflicts, accommodations, transitions, and national variants they condense are illustrated by comparisons of key contributions to ongoing debates in France and Britain from the early nineteenth century to about 1880.

The period in question saw an emphatic shift in thinking about unity and diversity in the natural history of man, with belief in racial differences steadily outfacing the doctrine of human similitude. Anticipated in the semantic history of race, vocabularies of difference hardened, initially in Germany and France and somewhat later in Britain. As with changing usage of the word race, the relative emphasis on human unity or diversity is usefully mapped across the published corpus of several prolific, long-lived authors. The conundrum of diversity in unity dominates the writings on man of Buffon, who vigorously defended the orthodox position that all human beings belonged to a single species but eschewed classification while exhaustively cataloguing the ambiguous, mutable division of humanity into variétés or races. Blumenbach's lengthy intellectual effort to reconcile his belief in 'the identity of mankind as a whole' with the 'phenomena of corporeal diversity' was an ongoing preoccupation evident from his earliest work in Latin, which classifies mankind into four flexible varietas, to his later works in German which redefine varieties as five hereditary Racen or Rassen.^[41] Prichard (1836‑47, I:vii, 2, 9), too, always upheld the 'common parentage' and 'unity of species in all human races', despite 'the striking diversities in their aspect and manner of existence' which he spent forty years cataloguing anatomically and attempting to explain along historical or linguistic lines.^[42]

In 1800, the French zoologist Etienne de Lacépède (1756-1825), who continued Buffon's Histoire naturelle, opened his zoology course at the Muséum national d'Histoire naturelle with a lecture on 'the races or principal varieties of the human species' whose original unity he took for granted. However, he invoked a kind of congealed late Buffonian biology to argue that at a very remote epoch, when climatic extremes were great enough to 'deform' the human body's 'most solid parts', there had been a radical organic differentiation of the human species into 'at least four races': 'Arab-Europeans', 'Mongols', 'Africans', and 'Hyperboreans'. He speculated that the Americas might originally have been occupied by a fifth, 'very distinct', 'truly aboriginal race'. The only Oceanian people to figure in this schema are 'the Malays' whom Lacépède thought were probably Mongols but might be descended from 'individuals of the European race', specifically Arabs or Phoenicians. They had ranged far beyond their place of origin in the Malacca (Malay) peninsula to settle New Holland, New Zealand, the Pacific Islands, and perhaps Peru. He also endorsed Buffon's argument that in 'very civilized countries', 'the art of man' could 'counterbalance the influence of climate'.^[43] Two decades later, Lacépède (1821:383-94) revisited the theme of human diversity in a dictionary entry on 'Man'. The tone is markedly harsher and the terminology Cuvierian. Still 'alone in its genus', the human species was nonetheless divided by 'particular hereditary conformations, produced by constant general causes, which constitute distinct and permanent races'. Lacépède's 'great races' have shrunk to Cuvier's standard three — Caucasic, Mongol, and Negro or Ethiopic — which he sharply differentiated according to 'distinctive' physical characters, especially a marked divergence in facial angles.^[44] He also identified several 'independent' lesser races. One was the Malays, whom he praised as 'active, audacious, intelligent' and positioned racially 'midway between the Mongols and the Negroes'. Another was 'the Papuans' of New Guinea, New Holland, and New Caledonia whom he vilified as 'the men least favoured by nature' and racialized as 'Asiatic representatives' of Africans but positioned even further from 'the Arab-European race' in physical conformation and their 'almost savage state'.

Notwithstanding his commitment to racial taxonomy and his adoption of a biological terminology to describe it, Blumenbach always insisted that any division of the single human species could only be 'arbitrary, and not at all clear-cut' because all 'national' somatic differences ran into each other 'by so many nuances' and 'imperceptible transitions'.^[45] The earlier Lacépède (1800:7, 16-20, 30‑1) allowed that the transition from the 'ignorance' of the 'semi-savage state' (epitomized in 'the African race') to the 'science', 'industry', 'ethics', 'sensibility', and 'reason' of civilization (epitomized in 'the Arab-European race') involved myriad 'insensible nuances' over an 'immense time'. But the idea of nuance is absent from Lacépède's later work and was evidently also lost on his Muséum colleague Cuvier who acknowledged human unity at the higher taxonomic levels but was noncommittal about the singularity of the human species.^[46]

From Linnaeus to the early Lacépède, Enlightenment classifications mostly recognized the potential equality of all human beings in contradistinction to other animals and did not systematically rank the varieties or races into which the single human species was partitioned: such divisions were often taken to represent different stages along a unilinear trajectory of common human development from savagery to civility. But Cuvier's comparative anatomy entrenched racial inequality and hierarchy as immutable products of physical organization, notably the size of the brain as indexed by the crude gauge of the cranio-facial ratio: 'the more the brain grows, the more the skull that contains it increases in capacity; the more considerable it becomes in comparison with the face'. At the time — 1800 — the racial corollaries of his theory were still implicit but already damning: the area of a vertical section of 'the European' skull was 'almost four times that of the face'; the area of the face increased 'by about a fifth' in 'the negro', by 'only a tenth' in 'the calmuck' (Mongol), but by a 'slightly lesser proportion' in 'the orang-outang'.^[47]

That same year, Cuvier (1978:171-3) instructed impending voyagers to seek empirical confirmation of the undoubtedly marked differences between the 'races of the human species' in certain key anatomical features: 'the proportion of the cranium to the face [cranio-facial ratio], the projection of the muzzle [facial angle], the breadth of the cheekbones, the shape of the eye-sockets'. These 'diverse structures', moreover, appeared to have significant 'influence' on the 'moral and intellectual faculties' of races. By 1817 (1817b:273), he was drawing an unequivocal nexus between the size of 'the skull and the brain' and a purported 'cruel law' (of nature) which had 'condemned to eternal inferiority the races with depressed and compressed skulls'. In Le règne animal (1817a, I:82, 94‑5), Cuvier translated the 'distinctive' physical characters of his three major races into an explicit racial hierarchy expressed in an implicit history of racial progress or stasis: the Caucasic race was 'the most civilized' and 'generally dominated the others'; Mongolic civilization had 'always remained stationary'; while the component peoples of the Negro race had 'always remained barbarians'.

Cuvier's adamant biologism was reinscribed in Britain by the surgeon and comparative anatomist William Lawrence (1783-1867) whose 1818 lectures to the Royal College of Surgeons on the organic nature of life and the natural history of man provoked a storm of criticism when published the following year. His stated aims (1819:119) were 'to consider man as an object of zoology' and to explain 'the principal differences between the various races of mankind'. The perennial tension between human unity and diversity is patent in this book's incongruous mix of scientific logic with humanitarian or relativist gestures and a priori racial essentialism. Lawrence dedicated his work to Blumenbach; praised Prichard; condemned slavery as 'revolting and antichristian'; proclaimed man's 'broad' distance from 'all other animals'; and asserted human specific unity: 'the various races' were only 'varieties of a single species'. Yet, (unlike Prichard), he refused on the grounds of inadequate 'data' to consider the question of whether all men 'descend from the same family' or to affirm 'that all the varieties of man have been produced from one and the same breed'. He maintained 'unequivocally' the structural approximation of 'the Negro' to 'the monkey'. He lionized Cuvier and echoed his position on the biological discreteness and differential endowments of races: 'comparison of the crania of the white and dark races' revealed 'the retreating forehead and the depressed vertex' of the 'dark varieties' which determined their 'moral and intellectual inferiority', 'limited' their 'natural capabilities' for civilization and Christianity, and ensured that 'Negroes' were 'every where, slaves to the race of nobler formation'.^[48]

At the time in Britain, such racialist views no doubt struck popular chords but they were also widely denounced, in large part because they raised the spectre of heterodoxy emanating from France. Philanthropists and Evangelicals accused Lawrence of materialism — because he maintained that life and thought were purely organic — and of denying the equality of all men before God; Tories deplored his democratic politics; and the book was denied copyright and withdrawn from publication. This ensured its success since it circulated in numerous pirated editions for at least the next fifty years.^[49] During this period, Lawrence's derivative but accessible synthesis of recent thinking about heredity and race formation was cited approvingly across the spectrum of the emerging British science of race: from Prichard, to the pioneer fieldworker, collector, and evolutionist Alfred Russel Wallace (1823‑1914), to the anti-evolutionist, extreme racialist anthropologist James Hunt (1833-1869).^[50]