[Humanity has found a way to be immortal, and spread among the stars. On your 21st birthday, you find out that you are the first person in 10,000 years that the process doesn’t work on.]
Immortality is a necessity for anyone who wants to see how the other half lives. Cryosleep is not the viable option it used to be, what with the unfortunate number of ships that end up crashing into a rogue moon, get atomized by a pulsar, sucked into a black hole. Manual input is required for interstellar travel now, and being immortal helps when you have to spend a few decades plotting a course around a nebula. “Space” is a bit of a misnomer these days.
"Hmm." The Granter retrieved the wand from my wrist and looked at my face curiously, then scratched his chin. "That’s… hmm…"
There is now a way to prevent DNA from decaying, to repair damaged cells, to “teach” them to know when to die and when to keep going. We can replace missing limbs, organs, bones with identical copies. We can—and we have, for the last 10,000 years. We’ve effectively turned the gun on the Natural Order, which is a nice change of pace.