well nick, there is no actual proof that the pheremone theory is rubbish. Just because it was in the games doesn't necesserily mean it is incorrect. Granted, the games do make up a whole lot of [email protected]
, but there is no actual proof of how xenos detect their prey. The pheremone theory is actually quite probable, aside from that, another likely theory would be that aliens can detect electromagnetic impulses, much like a shark.