I always thought the answer was that Unix was the aliens operating system and had been revered engineer from the captured alien ship in the late fifty's.
I mean come on you don't think "grep" is a human command do you?
That and the fact that they were using an Apple computer, which won't even interface with an ordinary human PC, nevermind alien technology...
:-)
Well, not in the apparently-singular form, but append an "s" and it's inevitable after a beer.