Hmm, a prequel would start plugging the gap in the timeline between the AVP series and the original Alien movie. Well, they only have what, a couple hundred years or so of time to fill?

You know, you can beat something to death, even an Alien...
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)