In a telling phrase, written in 1953, the English historian Gerald Reitlinger described Heinrich Himmler's background as "depressingly normal."
Why "depressingly"? Because presumably we should prefer to see a list of huge traumas peppering the background of the major Nazi war criminals, which might account for their subsequent aberrant behavior.
In Joseph Mengele we have another example of what Hannah Arendt once called the "banality" of those who committed crimes against humanity. Mengele was born into the most prominent family of the small town of Gunzburg, about half way between Stuttgart and Munich. There is nothing in his past to suggest that he would become the evil doctor who decided who was and who was not suitable for transfer to the gas ovens at Auschwitz, or that he would earn such nicknames as "Angel of Death," "Angel of Extermination," or quite simply, "The Butcher."
According to Gerald Astor, Mengele "was not a TV type homicidal maniac who lived only for the pleasure of killing," nor was he "even neurotically impaired by anxieties or phobias." Further, there is "no indication of sexual problems . . . that would distinguish him from most normal men. . . ."