There are many other structures around the world that could not have been built without a little help from our friends In your opinion, yes. You can't work out how they could have done it, so you assume alien help. What about the pyramids? We still haven't worked out how terrestrial did it, so do you assume that aliens must have helped or did it?
It seems that your view is based on: we can't work out how terrestrial could have done it so aliens must have helped or done it. My view is that we don't know and the jury is still out on the issue.
