Its after all a ring right? well then...it can be after all a finger too :) variation of xpression,evolution of communication as a whole from the bygone days is significantly interesting. Human beings perhaps the only species having the most complex patterns of communication. Its equally interesting how these have evolved across various cultures & traditions. below is one video which explains the 4th finger & its significance in Wedding -explanation as per Chinese (by the way Palmistry has some great perspectives on each line,alignment of the fingers & the hand on the whole)