“All his life he had wanted to be known by just one person. That’s what love was, he decided. Love was being known.”
Zero has given up on his life a long time ago. After the awful weight of rejection by his college sweetheart, he signed up for Lear's program because he saw no point to accomplishing anything with his life. All he wants is to be understood. When Alicia shows up and patiently listens to his story, he allows her to stay because she is now the best equipped person to fulfill that desire for him.
“A lot of life, Michael had learned, came down to trying to fix things that weren’t fixable.”
Michael has seen his fair share of disappointment. Namely, he lost Amy. He pours all of his efforts into refitting this ship in order to save humanity, but deep down he knows the project is doomed. If the virals don't show up before its completion, he still is banking on a minute chance of there being a safe haven based upon a rumor.
“That was the heart of the matter. A new world was coming; a new world was already here. Maybe that was what getting older taught you, when you looked in the mirror and saw the passage of time in your face, when you looked at your sleeping daughter and saw the girl you once were and would never be again. The world was real and you were in it, a brief part but still a part, and if you were lucky, and maybe even if you weren’t, the things you’d done for love would be remembered.”
Each of the main characters of the story believe in a greater good than themselves. They all are convinced that they have been chosen to sacrifice themselves for the survival of humanity. They understand that none of them are likely to survive the war, but they hope to be remembered because that would mean they were successful. If people still exist one hundred years from now, then they will be living memorials of the love of these heroes.
“All stories end when they have returned to their beginnings.”
This bit of prophecy proves true in this case. Amy and her allies are hoping to give humanity the opportunity to start over again. Their quest will be complete when there is once more a mother colony from which the entire globe can be propagated. Reverting human development all the way back to the stone age, they are ensuring its survival. The end becomes a new beginning.
