Dancing as a social function is, to the best of my knowledge, first mentioned by Homer in the 18th song of the Iliad, when he described the shield for the new armament of Achilles:

Also did the glorious lame god devise a dancing place ... There were youths dancing and maiden of costly wooing, their hands upon one another’s wrists ... And now would they run round with deft feet exeeding lightly, as when a potter sitting by his wheel that fitteth between his hands maketh trial of it whether it run: and now anon they would run in lines to meet each other. And a great company stood round the lovely dance in joy; and among them a divine minstrel was making music on his lyre.

Obviously, this was no religious dance (as the dances described in the Old Testament). Neither was it done to entertain an audience - though an audience was present. The main purpose was to provide a function where the sexes could meet under social control. And it seems, they did some kind of contra dancing, now and then.