Beth: It's possible this is the only one of its kind.
Ryan: How would that work? Doesn't natural selection cull the old?
Beth: Not necessarily. Natural selection is simply a description of what currently is alive. It doesn't actually care if you reproduce or have others of your kind, or how long you live.
Right now, we have a creature in front of us that is potentially millions of years old. However it got here, whatever path it took must not have killed it. And that is all natural selection needs to be satisfied. It's apparently so well adapted that it doesn't need offspring for there to be a copy of it here in front of us. We're getting a live performance by the original itself.
Ryan: But nothing on earth lives that long. If all you need to do to avoid being selected against is to live a long time, why don't we see that on earth? Isn't all this procreation stuff a lot of unnecessary work when you can sit back and just not die?
Beth: We don't see individual organisms that are millions of years old, but we see organisms that are certainly thousands of years old. Giant Sequoias live in a tiny region of the Sierras where they were still well adapted after the last ice age.
The reason that's the exception rather than the rule is that you have the odds working against you. The longer you're in exactly one place, the higher the chances you'll run into something that kills you. A forest fire that gets too hot, some lumberjack comes along.
If, like animals, you store your energy in a dense easily-accessible form... Well look out. You're a target for other animals who want that energy. And while you're locked into the same strategy you were born with, the predators are evolving. Over time, the advantage of being able to evolve trumps the survival advantage of just not dying.
With offspring, your genes can be in lots of places at once, instead of just one. Kind of like making backups. This helps your genes survive freak accidents. If your offspring can communicate with each other, they can even improve their overall odds of survival by coordinating. Effectively this is a large superorganism, designed to safeguard your genes.
From that perspective, the organisms we see on earth are millions or billions of years old. We could consider humanity an organism that has survived a very long time.
Ryan: So what does that mean for this creature?
Beth: It means this creature did all of that with no help. Somehow, it survived millions of years in the same body. It out-competed all offspring looking for the same resources. It survived all predators, all freak accidents, and apparently even the vacuum of space.
Ryan: How could it ever do that without evolving?
Beth: By being very, very smart.