The engineers and The space jockeys

So we all agree for the most part that the engineers had a civil war going on, but do we know how long it has/was going on for what if it was long enough that they diverged into separate evolutionary lines similar to darwinian finches, that way the engineers and the space jockeys are part of one species but on opposite sides that would explain their difference of architecture because if you look at the design of the juggernaut and the derelict they are obviously different but also very similar because they are based on the same base design, if you think that this might be unlikely I point you to the super predator and predator as they have been stated to be in a 'civil war' of sorts and that it has been going on for a long time which would obviously leave a possibility open for an evolutionary deviation. I purpose that it might have to do with the creation of life because I believe that the space jockeys believed in a more direct approach of creating life, being able to manipulate it as the species progresses to create a more "perfect" form for the organism, while the engineers believed in a more relaxed approach where they start the process and then step back and let what ever happens; happen, meaning perhaps the large beings in the murals, might not have been the engineers but rather the space jockeys, I say this because the giants are shown to be three to four times the size of the humans, now I realize that the humans depicted in the murals are shorter than modern humans but this would make sense because the space jockey is around four times the height of an adult human, and it might have gone to earth believing they would help them to kill of the engineers, which would explain what attacked the facility with it being the space jockey, now yes I realize that there was a roar that some people are saying is the deacon's roar but it doesn't sound like it to me, it sounds more like a battle cry, and this would explain why the black goo's effects from the prologue which was shown to break down the DNA of an organism and allow for a recombination, which takes place before the outbreak and after it is shown to mutate, so who is to say that if the space jockey's did invade the facility that they wouldn't tamper with the black goo so when they went to use it, it wouldn't do what it was intended to do, so they weren't going to earth to wipe us out but rather keeping track of our progress as a species, which would explain why the engineer didn't attack the humans immediately but rather with curiosity as if he didn't know why we were there and waited until after david mentioned that weyland created him the engineer responded with curiosity then fury.