well, from just looking at the truth video i can assume 1 thing, things are sure not what they seem. it is apparent at the end that Those Who Came Before have access to very advanced technology, this dont mean they are aliens, maybe those who came before are humans that are extremely different, and reshaped humanity for far more physical tasks. Since these people knew humanity wouldnt just obey them, they created pieces of power, which had very special purposes. the Apple is a piece of eden, which gives the owner practically limitless knowledge, altair used the apple quite a few times. those who came before did as well. Adam and Eve must have been some sort of offspring that were immune to the effects of the pieces of eden, which control minds, maybe through glands or sections and waves of the mind, this would make sense because it seems altair and ezio are immune to its mind control effect, but not immune to its other effects. Minerva is supposedly a god, mainly from this advanced tech, when Adam and Eve stole the Apple from eden(the tree of knowledge, which seems to be right in plain view of kilimanjaro)
ok so we have dealt with the fact that the pieces of eden are technological masterpieces, we also know they have failsafe locations of all the other pieces of eden, which dont have to be apples, Arthur is said to have the sword, as well as joan of arc. Minerva says that Adam and Eve incited rebellion among humans for their actions. with superior numbers, human overpowered those who came before and scattered the mind control devices. but over time, as humans progressed, people found these pieces again, and used them for power and their own uses. Templar order is founded to rule the world, big surprise. they followed god trying to find god, they found pieces of eden. heres where AC1 shows up. Al mualim may not be a templar, but he wanted power, at all costs. the people who were in that tomb under jeruslaem were templars. Mualim wanted them dead so his competition would die...literally. he used Altairs want to be accepted by him to his advantage. with all of them dead, al mualim tried to kill altair, but our hero killed him. and like many people before, mualim fell with the apple in his hand...and altair was tempted by it. limitless power and knowledge is kinda hard to pass up. Abstergo uses the map the piece brings up to find more pieces of eden, for what would seem like a device that would harness its power to enslave the world on December 21st, 2012....yeah...
so altair writes his codex, his journal of what happens after AC1, he had 2 wives, i think both died, but he had kids. he saw that video of the truth, just like subject 16. it haunted him...serious, badass altair was brought insane.