"One of the leading research efforts of Germany’s racial hygiene institutes was twin studies (for example, studies of identical twins raised apart) designed to determine the relative importance of heredity an environment. Suggestions that the study of twins might be used for this purpose date back at least as far as Francis Galton’s 1875 “History of Twins as a Criterion of the Relative Powers of Nature and Nurture.” In the Third Reich, twin studies were lavisihly funded as part of an effort to prove that heredity was the key to many human talents and imperfections. Twin studies purportedly demonstrated the heritability of everything from epilepsy, criminality, memory, and hernias to tuberculosis, cancer, schizophrenia, and divorce. In 1933 Otmar Freiherr von Verschuer published a book purporting to provide exact ratios of the relative influence of heredity and environment in a wide range of bodily traits; he derived his data from the study of several thousand identical and nonidentical twins. (see Figure 8). Verschuer’s studies were followed by hundreds of others. By 1936 Otto Reche’s Institute for the Study of Race and Volk had examined 12,50 pairs of twins, recording forty-two separate physical or physiognomic traits for each pair. Eugen Fischer called twin studies “the” single most important research tool in the field of racial hygiene; Verschuer called twin research the “sovereign method for genetic research in humans” Racial hygienists were able to convince Nazi authorities that twin studies warranted substantial government support: in 1939 Interior Minister Wilhelm Frick ordered the registration of all twins, triplets, or quadruplets born in the Reich, for the express purpose of research to isolate the effects of nature and nurture in the formation of the human racial constitution."