The persistence of eugenic themes in cinema over the last 100 years reflects fundamental societal beliefs about heredity's role as the source of social problems. From its earliest days science fiction cinema's critiques of eugenics were not aimed at the movement's underlying assumptions that humanity's fundamental nature lies within its genome and its relationship to social problems. Most science fiction films either implicitly accept these assumptions or incorporate them into their narratives and visuals. At the same time, however, these films criticize anyone who would change human heredity. By accepting the proposition that the essence of humanity, both the good and the bad, is deeply rooted within our genome, science fiction films take a conservative stance by critiquing any attempts to change the elements that make us "human."