if theres all these different lifeforms, with eons of a head start compared to us, there has to be some kind of concrete evidence of their existence at this point, .every 1 of them would have been trying to find others as well.  I dont buy it, I actually think we are alone in this universe,(reply>), And if one of them actually cracked time travel with their millions of years head start,  obviously that would be unmistakable as well, so time travel is impossible also