The Dark Triad Abnormal Development or Base Human Nature?
The Dark Triad traits you speak of are subclinical personality traits, therefore they cannot be diagnosed. Everyone carries some of the characteristics of these traits. People high on these traits are also not considered to be defective, even better they may in some environments be considered to be an advantage (e.g., business areas).

You may want to read up on research on the Dark Triad, mainly that by Dr. P. K. Jonason. He is one of the main contributors to the Dark Triad research and uses an evolutionary paradigm to discuss his research, showing how the Dark Triad may be adaptive.