Scientifically, hypothetically, or in plausible fiction, is there any possible fluke of the genetic code or something similar which could cause a person to stop aging?

Death?
You will stop aging on the spot when death happens.

I suppose that’s why so many tales of immortality or supernaturally prolonged lives involve death or :undeath” —but death isn’t really life, and the dead don’t live.

So, the question remains—what could happen to make a LIVING person meet a certain age, certain nutrients, or just in the genetic code, their needs are sustained and they live indefinitely at that stage of development. Yes, they could still die from being killed or even disease. But they stay that same age.

It doesn’t work to say someone hasn’t seemed to age in 36 years because they are dead.

No, it is not plausible.
We do not get wrinkles, or other aging issues from a genetic code. The signs of deteriorating is simply a machine worn out.

If you are thinking of a reversal to what they did with the salmon, it won’t work. What they did rushes the fish to sexual maturity more quickly.

Endocrinology would be a more likely place to look, I believe.

It is a very clever thought, though. I think you should run with it. See where it takes you.

Can you cite a single example in the billions of people who have walked the earth of an individual displaying such a trait?

Aging IS built into our genetic code. Or rather aging occurs because there is a built in limit to the accurate number of divisions in our replicating cells. I suspect that my grandsons will live to see the day when the aging process can actually be arrested. And with that, they should easily survive to see the aging process reversed. Too bad we were born just a couple of generations too soon. But on the other hand, the problems that are going to confront my grandsons and their offspring—I don’t envy the possible nightmares confronting future humanity.

I’m not a scientist, but here’s some info and some guessing:

Possibly, there could be a mutation that inhibits the signs of aging like the person wouldn’t get wrinkles. They already say getting wrinkles is partly genetic, and not just a matter of melanin.

As far as internal aging, the way I think about it is our organs get damaged over time, and we stop producing new healthy cells at the same rate. Also, our fighter cells get overwhelmed over time. I think we can see that some people genetically do much better than others. Some families have many people who live long lives, while others have many people in the family who die young. Sometimes we see it’s caused by the environment, but other times it looks to be genetics more than anything.

One problem is cell production when it is out of control (growing and growing) is basically cancer. So, the body needs to keep in balance cell growth and death. People who have better balance, and strong mechanism to detect and fight stray bad cells do better and live longer. The FOXO gene and the study of telomeres would interest you. Here’s a link to a video about FOXO. https://www.pbs.org/video/nova-sciencenow-can-we-slow-aging/

I once read an article about a mutation believed to be the key for surviving the plague. The scientists also determined the same gene protected people from HIV. I’d lay money on a man I worked with who became HIV positive when so many of his friends were diagnosed also. His partner died from it within years. My coworker never became sick. He was positive, but never sick. He was diagnosed in the late 80’s I think, latest would be the early 90’s. He’s in his 80’s now. His father lived to be 99. His family just lives long. Link about the mutation https://www.pbs.org/wnet/secrets/mystery-black-death-clues-evidence/1490/

This link talks about telomeres, but previously I’ve linked a video, it was a program I saw on TV, that was easy to follow, and in my opinion easier to follow. If you can get the search engine to work you might find it. Here is the another link though https://learn.genetics.utah.edu/content/basics/telomeres/

I’ll toss out a fictional but theoretically possible method.
Using a CRISPR-Cas tool a scientist splices in a DNA stopper more permanent than the existing telomeres at the end of our chromosomes.
DNA stops degrading and cells stop aging.

Taking the fiction further…. To reduce costs, Insurance companies and agents from the Social security department start sending out hit squads. A $5000 hit has an investment payback period of 6 months. That is an enticing proposition for the money managers.
They hire younger generations to do it.

@LuckyGuy Check out my first link about FOXO if you haven’t heard of that before.

An inventive writer could come up with any number of ideas to make immortality at least sound sound plausible. How it is done doesn’t matter, if the story is good the reader will willingly “suspend disbelief”. I don’t think an explanation is even necessary.

I have studied up on the FOXO 3A gene and was tickled to find I have the good variant. I think it is theoretically possible to stop or even reverse aging with technological intervention. I would not think there is any evolutionary advantage to this on a species level so that’s probably why most organisms are programmed to die. I have heard certain lobsters can live a very long time and that tardigrades and some jellyfish are immortal as far as growing old.

Add the Hydra to the club.

Immortality didn’t get them very far.

I remember that now too. Immortality is great for “you” but bad for “us.”

Life happened, right?