What are the spines on a xenos back for?

will before we consider that consider what your hair does. its usless so thats probally like there usless part.

actualy hair is used as a form of insulation
if we didnt have hair out core body temp wud drop like mad

There is a theory that the spines help them breath underwater. I don't know if it's true or not because it came out of a book. It's suppose to filter oxygen from the water like gills.

I have a wild theory about the spines being there to keep the rest of the bones from faling apart... but ofcourse, if by spines you mean the tube-like things, then there are a few other threads about them..., in which it ois said that they`re even for breathing, though aliens don`t breathe, either for resin secretion and there may be others, but i can`t remember them.

Actually, its a defense mechanism(theory) to make it look bigger than it really is. Warrior aliens(aliens hosted from humans) satnd around... let's say 6'6". They look about two feet taller with those spines. The Alien/Dog hybrid in Alien 3 was actually about 6'9" standing straight up, so it would not need these because it is already a large and frieghting predator (not Yautja, but ya get my drift?). So we can assume that the Predalien is gonna be about 8'5" so it most likely won't have these spines. Oh and we don't "thing"

I agree with Pred428. I think they are used to breathe underwater because in Alien Resurrection the spines seemed bigger than they are in any other movie. Plus in Alien Resurrection the aliens are underwater for a good amount of time.

yup about 20 seconds...

anyway, that underwater breathing thing would screw up the whole biology that our long lost friend whom i hat... apreciated so much, Crow, has bothered to put together, because in that biology the aliens didn`t breathe. At least in some of the topics. In other they may have been breathing something...