I got this tid-bit from SONGfacts :
This song started out as an Andean folk melody that Paul Simon came across in 1969 when he played a week-long engagement at a theater in Paris along with the South American group Los Incas, who played an instrumental version of the song called "Paso Del Condor." Said Simon: "I used to hang around every night to hear them play that. I loved it and I would play it all the time, and then I thought, Let's put words to it."
If the site is accurate that he did discover it
specifically in 1969,then Wikipedia (big shock) is incorrect.
http://www.songfacts.com/detail.php?id=2550