Bottom Line: This is MESSED UP.
It is NOT the same song. No one, ever would convince me that it is. Law be damned.
WHat are you talking about? Once sounds just like a modern cover of the other, with some different lyrics:
http://www.dailymotion.com/video/x1edjqg_marvin-gaye-got-to-give-it-up-1977_music
https://www.youtube.com/watch?v=yyDUC1LUXSU