I am curious about why it is so universally established that Jesus had long hair and a beard. I guess this must have settled at some point, and for some specific historical reason.
Interesting question! I've taken the liberty to cross-post this to /r/AcademicBiblical and, hopefully, we'll get some good answers. The direct link is here.
Curiously, the long hair would seem to be excluded by 1 Cor 11:14, which has: "Does not the very nature of things teach you that if a man has long hair, it is a disgrace to him...?"