ArgumentIn 1909, Italian zoologist Daniele Rosa (1857–1944) proposed a radical new evolutionary theory: hologenesis, or simultaneous, pan-terrestrial creation and evolution driven primarily by internal factors. Hologenesis was widely ignored or rejected outside Italy, but Swiss-French anthropologist George Montandon (1879–1944) eagerly embraced and developed the theory. An ambitious careerist, Montandon’s deep investment in an obscure and unpopular theory is puzzling. Today, Montandon is best known for his virulent antisemitism and active collaboration with the Nazi occupation of France at the end of (...) his career. By that point, however, he had quietly moved away from hologenesis. This shift has gone unnoticed or been left unexplained in existing research. This article reexamines Montandon’s theoretical outlook and reasons for championing Rosa’s forgotten theory. It argues that while Montandon’s adoption of hologenesis arose from a complex blend of scientific and personal factors, his previously overlooked early fieldwork with the Ainu played a key role. In contrast, hologenesis did not inform Montandon’s later public antisemitism. (shrink)