So the Nazi's were a large, bureaucratic organization, and despite that it seems like our 'winning strategy' was to kill large numbers of lower level people, and smaller numbers of higher ranking people, and yet it seems to have worked in the end? The claims made by this paper seem very silly.
I doubt it because we would be deluged with holidaying spherians every long weekend. Earth beaches are the best. Also the construction process would have generated a lot of debris. Seriously, it is too close not to be noticed as such. If they were humans there would be trillions of them in there. Even if it was a ringworld sort of thing with a collapsed civilisation, there would be ships coming past and making radio noise, exhaust, etc.
Why do you think you have any idea what we would see or not see?
Imagine you were living with circa 1800 AD technology, and were looking for evidence of another civilization with circa 2014 technology. Keep in mind that this 200 year difference is nothing compared to the difference between modern technology and the technology of a race capable of building a Dyson sphere.
Perhaps you would use a rudimentary telescope to look out to sea. You would rule out any ships, since the weird objects you see don't have sails. If those giant things were ships, the sails would have to be miles across! So of course they are just some other phenomena, but they can't be ships.
Seeing a highway, you would know, obviously, that the things you saw weren't vehicles. Where are the horses? Plus, they are going far too fast. Besides, it couldn't be a road because there aren't any seams, and any road would have to be built from cobble stones. Clearly these are some other phenomena.
Besides, how could cities that far apart communicate effectively without Semaphore Towers? The lack of Semaphore Towers proves there is no way those big things on the horizon are cities. An envelope calculation shows that civilizations of that huge of a size would have to have at least 45000 semaphore towers between them just to negotiate the marriage of members of the royal families! http://en.wikipedia.org/wiki/S...
Plus, if you have a Dyson Sphere, why would you need to send any ships anywhere? To trade? Trade what? Communicate? Why would you use a ship to communicate? If you did send ships, why would they go through our solar system?
For the same reason we still write text-based stories, send text-based emails, text based text messages, etc etc.
There isn't a way to express tree structures directly, without jumping back and forth, so we have settled on (or evolved to) a standard way to linearize such structures, which is called grammar.
There's no advantage to any other representation, but rather there is a huge disadvantage to other representations because our brains have spent the last million or so years evolving to be adept at manipulating language in this way.