What if the different planets had different Bio-engineering technology, and were activated shortly after the Traveler entered the Sol System? There might be another alien race out there, pulling the strings on the Fallen, Hive, and Cabal. The Vex could be the sleeper agents of {[i]Mystery Aliens name here[/i]}, or they could be like the Cylons (hesitation on Skynet getting pregnant part) [quote]"after coming off of a week-long bender with some hard-partying Cylons, Skynet got pregnant & had the brilliant idea of making a bunch of babies with triceratops heads." -DJenser Feb 18 at 10:39:34 AM Permalink [/quote] An even better example would be the Geth from Mass Effect 3. The Fallen and Hive resemble Human anatomy pretty closely (Bio-engineering on the arms, since the lower caste of the fallen only have two arms, yet they have armor similar to the Guardians). I don't know about the Cabal, though... They got me on that one.