Euler studied psychology at the University of Bonn/Germany and at Washington State University in the US, where he also received his Ph.D. in 1972. From 1974 to 2009 he held full a professorship of psychology at the University of Kassel/ Germany. Since his retirement in 2009 he has been working as a visiting scholar at the German Universities of Frankfurt/Main and Bochum, Departments of Phoniatrics and Pediatric Audiology, mainly in the area of language development and its deviations. His primary interest, however, has always been evolutionary psychology, although this approach did not get much attention in German psychology until the 1990s. For decades, he has specialized, particularly in family relations and sex differences, and is an acknowledged member of a group of international scientists who are committed to establish a sub-discipline delineated as Evolutionary Developmental Psychology.