Now, for the people who have seen the movie, here's my take on the plot; let me know what you think:
I think that Story 1 - the one about Spain & the Conquistador, never happened in the real world of the film - it is merely a story created by Izzy - the female lead character in Story 2 - the one with the doctor & the monkey. It, Story 1, is also a symbolic story - a tale - that hints at what will happen to the real person - Tom in Story 2, as he continues with his quest for immortality.
Story 3, the space story set in the future, is a continuation of Story 2. The male lead is the same male, Tom, from Story 2. The tatooing that he started in the modern time, our time, after Izzy's death, continued for hundreds of years & by the time we get to the space story, the dude is covered in tattoos. Also, the two stories being the tale of one character explains the flashbacks Space Tom has, flashbacks to Izzy in our time.
So what do you thinks? Does that make sense?