I stumbled on an amazing article called Bosom Buddies: A Photo History of Male Affection, and I'm forcing a tie in to my blog because people love using vintage photographs as art.
The thesis of the article is that the concept of a clear divide between gay and straight is relatively modern. In the days of yore, there was't a stigma attached to casual physical affection between male friends. Once homosexuality became a designated group, bros reduced demonstrations of affection so that no one would think, "Gay!". This is such a shame because the bromance in these pictures is the sweetest thing I've seen in a while.