So in a species that depends on pack/tribe behavior for survival, how is an inability to follow authority not a mental illness?
In a species (alongside a whole host of other species) that depended on rape for survival, how is an inability to rape not a mental illness? [1] In a species that depended on rigidly defined gender roles of women child rearing and men being hunters, how is aberrant behavior not a mental illness?
I think what's happening is you're falling prey to appeal to nature fallacy. Consider here also the results of the loners, the outliers, the dropouts -- a lot of them go on to contribute greater value to society than the ones following the pack/tribe behavior.
[1]: Researchers Thornhill and Palmer say rape is an evolved reproductive strategy and not a crime of violence. See their piece 'A Natural History of Rape: The Biological Bases of Sexual Coercion' for more.