imo acne has nothing to do with evolution, it's just a hormonal imbalance. could be triggered by many factors (including psychological devepment) as alambicated the ways of hormones are.
just 2 quick notes:
1. nobody in my family, brother/parents/grandparents ever had acne
2. statements like "the tribe people", "ancient", "isolated", "uncivilised" don't have acne make me want to have "acme". you just can't know if they have/had acne or not.
although, there are ancient writings about acne, so they had acne..
Acne is not a hormonal imbalance, most acne patients have hormones in the normal range.