Machine derived contents note: 1. The Darwinian legacy -- 2. The age of Spencer and Huxley -- 3. Crisis in the West: the pre-war generation and the new biology -- 4. 'The natural decline of warfare': anti-war evolutionism prior to 1914 -- 5. The Great War: man the fighting animal -- 6. The survival of peace biology -- 7. Naturalistic fallacies and noble ends -- 8. Conclusion