"Four and half billion years, why would you even do that?" Clara's Doctor Who is a literary figure of proportions so far greater than what humanity is capable of.
Somehow, Clara's Doctor Who gives me hope. Both Clara and number 12/13 embody selflessness at points in their timeline. The act of giving up one's freedom for a known or unknown death is a storyline created by Christ himself.
Whether these or previous writers knew it, the desire of the intellect to explain such a selfless act is always intuitive. There is more that we cannot see with our limited intellect.
Maybe that is why people cannot wrap their minds around the selfless act of the Son of God who died to save our immortal souls. Our intuition, if fostered, can see beyond the tracing that is left of the vision of the Cross. Intuition is more than made up nonsense because it is the longing of the soul to be whole again.
In the tv shows, we eventually see the end of the story or the end of the season and sometimes it goes the full circle giving explanation where needed. So you can see how an act of self sacrifice is in fact an act of freedom and love.
Christ is Himself, freedom and love. He is the full circle. Therefore the intuition, the intellect, the story of salvation are all founded in the selfless act of a God made man. Man hasn't even existed for four and a half billion years. Can you imagine if it would? Jesus Christ's sacrifice would still extend beyond that time as both the beginning and the end of freedom and love. You are free when you give up you.