How do you know the Shivan brain is biological?
Because the Shivans have expressly been stated by

to not be robots, that's how. They might be cyborgs, but they have biological brains and other biological systems. Surely if they had electronic brains that would have been mentioned in the intel briefings in the games? It seems like a rather important piece of information.
More to the point, if they had electronic brains they would in a sense be even more vunerable. You can't EMP a biological brain.
Originally posted by aldo_14
EDIT; if that's what your using.... because obviously using human or earth-based life isn't the best way to assess an aliens possible physiology.
That argument sounds nice, but it's invalid. Earth-based life, all of it, fits into those descriptions. If it were
possible for life to evolve unsloppy,
why did it not do so? Life evolved as it did because it provides some concrete advantage, otherwise it would have evolved differently. Unless the Shivans some evolved from completely different origins, and they did not since I cannot imagine it would not have been mentioned that they were tungsten-based or something, the argument does not hold water.