Systematic examinations of rescuers have actually shown a high degree of heterogeneity among individuals. Rescuers came from divergent social backgrounds, varied widely in terms of political and religious involvements, and displayed different levels of friendship and animosity toward Jews. None of these variables has turned out to be a reliable predictor of the sort of person who was more or less likely to rescue Jews.

Before the war, Mengele had received doctorates in anthropology and medicine, and began a career as a researcher. He joined the Nazi Party in 1937 and the SS in 1938. He was assigned as a battalion medical officer at the start of World War II, then transferred to the Nazi concentration camps service in early 1943 and assigned to Auschwitz, where he saw the opportunity to conduct genetic research on human subjects. His subsequent experiments focused primarily on twins, with little regard for the health or safety of the victims.[2][3]