When Perrin meets the Green Man at the Eye of the World, he says 'A Wolfbrother! Do the old times truly walk again then?'. Soon they will run with men again, to the Final Hunt. Some wolves claim to have memories of their ancestors running and hunting together with men. Stories of men running with wolves are older than the Age of Legends.
Not much is known about the origins of the condition except that it is 'older than the One Power', likely dating back to a much more primitive man.