In every generation, Assassins are real because theyre existed from Holy Crusade until today. It depends on "Assassination" of any political leaders. Some assassins in real world are bad, but some are good.
Assassins in their nature have existed for as long as there has been political opposition in any society. Assassins in the fashion of Assassin's Creed? I don't think so, those Assassins were formed in the 12th century during the Third Crusades and were snuffed out relatively early by Crusaders.
Yes but it is said that the creed is the only thing in the world that is idestructable as it only takes one person to start it up even if all its ormer memebrs are deceased, therefore if someone was to start the creed again it would be reborn.
I believe that there's no way for anyone to know for sure. Historical documents are written by the victors and scientist manipulated or those making fact of fragmented knowledge. Who's to say that they didn't, i feel if the idea could be conceived by us, ubisoft, and their inspiritaion than it could have been executed and could still possibly exist. Know one can know for sure. The truth lies within the land...blowing like the sand. I say trust what you feel deeply, all answers truly lie within ourselves.