[carumba]

To assume that men in prehistoric settings could not observe the sun, the moon, and the stars is far fetched. Are we talkin' about the planets? Now that is another matter.

[Junior]

Humanity knew of the existence of the closer planets (Mercury, Venus, Mars, Jupiter and Saturn) at least since the end of the stone age. Planets move differently in the sky than do stars and are easily spotted over several days of observation.