[ndsipa_pomu]

I think the problems with alternate theories such as Ancient Aliens is that they seize upon some examples of evidence (which are typically not great evidence anyway) and build a whole story on top of that. However, they then don't consider the ramifications of that - if ancient aliens did exist, then we should expect to find other sorts of evidence and thus make predictions about them. Of course, without predictions, theories are non-falsifiable and thus worse than useless.