*quietly raises hand x3*
Yep...Dave nailed it. What I fail to understand, however, is why the xenomorphs still looked as unaltered as they did. I mean we saw the queen, she was a mess, and let's not even talk about the Newborn.
I suppose the fact that the xenomorphs were sexually reproduced from the queen and consequently weren't directly related to Ripley could have something to do with it, but I would have expected them to look a little more different then they did...
And thus I clothe my naked villainy
With old odd ends stolen forth from holy writ
And seem a saint when most I play the devil.