I clearly recall a Gary Larson illustration showing that the the aliens at least eat turkey.
But seriously, can someone please give a reference to the idea that aliens are "perfect organisms", other than in the sense as relative to earth-evolved life, which is how I interpret the comments made by characters in the movies, who would have no way to know that the aliens were "infinitely adaptable" or other such BS.
If you read the original O'Bannon script you will see that the alien in Alien definitely grows to full size by raiding the food locker.
Because aliens clearly have a biomechanical appearance, I always assumed that in addition to organic material, the aliens grew by consuming metals and other inorganic materials found in space-ships and the colonies of technological species.
Also, according to the original O'Bannon conception, aliens are not "perfect organisms", they are just meant to be very 'alien' with a very disgusting and mysterious life cycle.
Certaintly they were not farming prior to terraforming the planet in Aliens, so there must have been pretty substantial food supplies in the colony, plus it seems logical to assume that a big portion of the alien diet is inorganic material. So I don't think it is a big deal that most of the colonists bodies were not consumed. Perhaps the reason the aliens in AVPR were weaker-skinned is that there was not sufficient high-grade metals in the Gunnison buildings for them to consume, compared to a ship like the Nostromo, or the reactor in Aliens.
just my two cents.
Obviously aliens must consume something to grow. Anyone who thinks otherwise is a moron who needs to take a basic physics class and learn about conservation of mass-energy.
