Perhaps this would normally belong in the game room, but due to the fact it touches on aliens and is
about plugging plot holes I figured it would be ok here.

Was lurking at the gearbox forums earlier this morning and saw this great continuity thread:
http://forums.gearboxsoftware.com/showpost.php?p=4395444&postcount=8

In it there are a number of explanations on why there are so many xenomorphs in the game, after reading
it, I thought I would share my own ideas and see what you guys thought.

My initial ideas regarding the large numbers of xenomorphs seen in the game and the unique versions was that
there might me some kind of 'underground ecosystem' deep underground on LV-426 that some xenos found and
bred in, which would explain why there are so many of them. However I have an alternate theory on how this occured, here goes:

When the Derelict crash landed on LV-426 many millenia ago, the climate was harsh but there was a thriving ecosystem on the planet with varying plant and animal life forms on the surface. They were no match for the new invasive species who multiplied out of control and killed off the native life forms rapidly, even devouring and devastating the local plant life. As this occurred, the already harsh environment of LV-426 degenerated rapidly, soon becoming the harsh unbreathable cold atmosphere we saw in the movie alien with icy winds whipping the now barren surface. Although the aliens were tough enough to survive
the new environment, lacking the resources and comfortable environment they were used to-they gradually moved toward the area of their origin, the surrounding area where the Derelict lay. There, they had numerous deep caverns to hide and burrow in to go into deep hibernation like many animals on earth for example: http://en.wikipedia.org/wiki/Biostasis http://www.earthrangers.com/wildwire/top-10/top-ten-hibernating-animals/. There they lay like the eggs in the Derelict, in a deep cold sleep close to death itself for thousands of years, not even noticing the change of atmosphere as the new colonists built atmospheric processors to clear the air for human consumption. However when the infestation of Hadley's Hope happened (perhaps the new xeno colony released pheromones or something similar to 'call out the troops') and construction of the Origin facility began-the once dormant aliens began to slowly stir out of their dens once again. While I think something that has acid for blood could find nutrients in consuming mineral deposits and stuff like that-I'm sure they have a nice taste for meat as well, which makes fresh humans even more useful!

Just my thoughts!

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When in doubt-fry the place from orbit!