Influenced by the German biologist and philosopher Hans Driesch, he became interested in philosophy of life and in a large work The History of Biological Theories (in German 1905–1909, in English 1930; reprint in 1988) he criticized the evolutionism of the 19th century.
According to Ronald Numbers, Ulrich Kutschera, a prominent European evolutionary biologist, concluded in 2003 "that anti-evolutionism in German-speaking countries has already infiltrated some academic circles".