Could it be that these "aliens" have stored information in our DNA, only to be solved by us when we reach a high enough technology?
Could these early paintings on cave walls have been experiences of people who had encounters with higher "spirits" from other worlds, or parallel universes, after using some kind of hallucinating drugs which made them travel to these other worlds? And could that be the beginning of spirituality and religion?
What actually happened about 35.000 or 40.000 BC when mankind began to develop more rapidly in relation to the period before that, from about 40.000 - 200.000 BC, when men where equally developed to the modern day men, according to brain capacity and the nerve system? It's not a coincidence, I don't believe that.