At a Washington science conference in the early summer of 1918, as the First World War was drawing towards its finale, the noted American biologist Raymond Pearl rebuked his fellow naturalists for failing to conceive of war as a biological event, ‘a gigantic experiment in human evolution’. Reluctantly he traced the war back to his hero, ‘that gentlest and kindest of souls’, Charles Darwin: ‘I believe it to be literally true that the one event in the history of Western Europe which more than any other single one laid the foundation for the situation in which Western Europe finds itself today, was the publication of a book called The Origin of Species.’ Pearl exemplified the schizoid tendencies that often prevailed in western thought about the connection between Darwinism and war. On the one hand, he blamed ‘the frightful welter of blood’ on the ‘gross perversion’ of Darwin's views by German biologists, who ignored the mental and moral qualities of humankind. On the other hand, Pearl himself saw humans as innately pugnacious and war an adaptive response to long-term evolutionary pressures. In this he anticipated the neo-Darwinist doctrine of modern sociobiology. In fact the ancestors of sociobiology on war and human aggression are to be discovered in the era from 1880 to 1919.

World War I seemed to validate images of violent simian humanity, while Allied propaganda magnified the demonic role of Prussianised Social Darwinism in causing the war.