Paul Broca was the foremost French polygenist and the leading physical anthropologist of his time. He located humankind squarely in the animal kingdom in close relationship to the anthropoid apes. The title of his Recherches sur l'hybridité animale en général et sur l'hybridité humaine en particulier considérées dans leurs rapports avec la question de la pluralité des espèces humaines (1860) expressly denotes polygenism, as does the use of the term 'genus' in the title of the English translation, On the phenomena of hybridity in the Genus Homo (1864). This work — which reads today like a racialist tract — advanced Broca's thinking about the relationship of racial interbreeding to the issue of polygeny. The question of whether interbreeding between different human groups produced fertile unions that continued over time was of much interest to anthropologists. Broca first investigated the products of interbreeding between closely related species such as rabbits and hares. When he turned to human groups, he proposed a range of types in terms of fertility of the offspring that he suggested were the result of different kinds of interracial union.[18] Quite a large proportion of this work is devoted to Australian Aborigines.
Broca sought to reveal what happened when the two most divergent human types — the purportedly most superior and most inferior — interbred. He designated the Germanic (Anglo-Saxon) as the most superior race and the Aboriginal Australians and Tasmanians as the most inferior, in line with the received hierarchical ranking of human groups by the scientists of the day. His only other contenders for the position of most inferior were the so-called Hottentots (Khoikhoi),[19] but he considered that they at least showed signs of 'improvability' while the Aborigines 'seem absolutely incorrigible savages'. While he expressed disgust at the 'execrable atrocities' visited upon them by the British, he wrote (1864:45-6) that 'the Tasmanians are, or rather were, with the Australians, nearest to the brutal condition'. Indeed, at the beginning of this work, he singled out the Australians, among all groups, as satisfying the conditions of a separate human species:
The term species, has, in classical language, an absolute sense, implying both the idea of a special conformation and special origin, and if some races — the Australians, for instance — unite these conditions in a sufficient degree, to constitute a clearly marked species, many other pure or mixed races escape, in this respect, a rigorous appreciation (1864:11).
Broca (1864:49) maintained that the 'ugliness and dirty habits of the native women' were not enough to deter men's sexual interest and went on to explain what he believed to be the scarcity of mixed-race children in the Australian colonies not in terms of the absence of sexual encounters between Europeans and Aborigines but as the consequence of a dysgenic match, of too great a separation between two racially quite distinct human types. His final conclusion (1864:60) about human hybridity as it related to Aborigines was 'that the lowest degree of human hybridity in which the homœogenesis is so feeble as to render the fecundity of the first crossing uncertain, is exhibited in the most disparate crossings between one of the most elevated [Anglo-Saxons] and the two lowest [Aborigines and Tasmanians] races of humanity'.
Broca's premise that unions between different combinations of races would produce differing degrees of fertility in future generations rested on a spurious hierarchical ranking of human groups. And his conclusions about the infertility of Aboriginal-European unions were later shown to be absurd. Here, then, is an egregious example of what Elkins (1999:169) termed 'ugly' racism, racism involving sexual revulsion or attraction. Broca's comments about 'native women' certainly suggest a sexual element. What it was that made him and many of his colleagues so ready to jump from anatomical researches to quite unsubstantiated and abusive rhetorical pronouncements about relative racial worth is a complex question that writers such as Gilman (1985) and Jahoda (1999) have tackled on a wide cultural, historical, and psychological canvas and Fausto-Sterling (1995) on a smaller scale relevant to this discussion. Whatever the particular combination of reasons in Broca's case, he was enormously influential. He died in 1880 but the imprint of his thinking about Aboriginal Australians can be discerned in the discussion that followed Topinard's 1885 presentation and particularly in Topinard's own contributions, Topinard habitually referring to Broca as his 'master'.