Bernhard Rensch (21 January 1900 – 4 April 1990) was a German evolutionary biologist and ornithologist who did field work in Indonesia and India. Starting his scientific career with pro-Lamarckian views, he shifted to selectionism and became one of the architects of the modern synthesis in evolutionary biology, which he popularised in Germany. Besides his work on how environmental factors influenced the evolution of geographically isolated populations and on evolution above the species level, which contributed to the modern synthesis, he also worked extensively in the area of animal behavior (ethology) and on philosophical aspects of biological science. His education and scientific work were interrupted by service in the German military during both World War I and World War II. Biography Rensch was born in Thale and as a young boy, he took an interest in observing the natural world and discovered a talent for drawing and painting. He served in the German army from 1917–1920 and began to observe natural phenomena while he was held prisoner in France. He returned to Germany and began his studies on feather structure under Valentin Haecker (1864–1927) who had himself studied under August Weismann. Until the 1930s Rensch held anti-Darwinian and Lamarckian views. Rensch also took an interest in the philosophy of science and was fascinated by Theodor Ziehen (1862–1950). Rensch also studied expressionist painting and in later life examined the biological roots of art. He received his Ph.D. from the University of Halle in 1922. He joined the zoological museum of the University of Berlin as an assistant in 1925. In 1927 he participated in a zoological expedition to the Sunda Islands. He studied the geographical distribution of subspecies of polytypic species and of complexes of closely related species with attention to how local environmental factors, especially climate, influenced their evolution. In 1929 he published the book Das Prinzip geographischer Rassenkreise und das Problem der Artbildung that discussed the relationship between geography and speciation. His work in this area would influence Ernst Mayr, who was also an assistant at the museum from 1927–1930, and would contribute to the development of the modern evolutionary synthesis. In 1937 he was forced to leave the museum because he refused to join the Nazi party, and took a position at a zoological garden in Münster. In 1940 he was recalled for military service, but was discharged for medical reasons in 1942. In 1947 he published a