Paintings like these are glimpses into Neolithic religious rites; see these from Australia, and note that were some see alien grays or space helmets I see witch doctors parading around with human skulls.
https://www.google.com/search?q=aborigines+aliens&espv=2&tbm=isch
Even these?
They are females from Planet Five, who took refuge --and husbands-- on Earth, after all their males were killed off in the wars that triggered run away planetary destruction. Today, we call their home "the asteroid belt".