[devb]

Sure. A dumb civilization could have done it too, perhaps as something to do with crystals or the Zodiac.

But in all seriousness, Occam's Razor is a great tool here. So far, every cosmological problem we believe we've figured out has occurred due to natural processes. There is very likely something we don't know about large scale structures (an understatement!).

[jonsen]

In all seriousness, civilizations, dumb or not, are natural processes. There is very likely something we don't know about advanced civilizations.

[mrfusion]

I guess another dumb question; what does Occam's Razor say about the Fermi equation?

[bashinator]

A couple possibilities that I'm aware of:

* All intelligent life goes extinct before achieving interstellar colonization, or is content to remain in their home stellar system.

* We are in the first generation of life in the galaxy capable of achieving interstellar colonization, due to the time scales required for sufficient heavy elements and evolutionary complexity to arrive.