# How many generations of descendants could a person plausibly outlive?

People live longer nowadays than they used to - but a big reason for that is that our elder care is much better. With a daily pill or two, the body's failing systems can be sustained.

In my story, I want a person to live a very long time...but their children, grandchildren, grandgrandchildren, etc are out of luck! For whatever reason (I'm thinking general societal decline) the lifespan of subsequent generations has shortened dramatically. But as I mentioned above, a decline in the quality of medicine threatens the health of elders. I need some kind of plausible reason that the old generation has a long lifespan, but the later ones do not get this benefit, and in fact their lifespans shorten.

What is a plausible reason that this could happen, with 20-minutes-in-the-future technology? How old could the long-lived generation get, and how short can we cut down the lives of subsequent generations without threatening that longevity? Ideally this would be something that the elders could not stop, even though they want to. "We hog the meds, none for you" is a little too evil.

• Even though we may live longer (on average), this is mostly a function of a lower infant mortality and less so to adults living that much longer. If 2/3 of those born die in infancy and the rest live to 60 years old, the average age that the entire population lives is 20 years old. – Mark Ripley Mar 11 '17 at 11:29

Here's the best I could come up with:

The tech used to make them live longer is now illegal thanks to side effects which only affected a small percentage of the population, but, for some reason, any children that they have are more likely to suffer from that side effect. In other words, the younger generation can't take the miracle pill because it is almost sure to cancer or dementia or psychosis or whatever you like by the 3rd generation of taking it. Even if they hold off taking the miracle pill into their golden years so that the next generation CAN take it, the publicity from the bad cases might mean that the government has limited the pills to only be accessible to those already taking it, a concession they were forced to make by those who had lots of  and were not suffering from the side effects. There will, of course, be a black market as well...

How old could the long-lived generation get, and how short can we cut down the lives of subsequent generations without threatening that longevity?

122 is the longest a human is supposed to have lived, but it's hardly common--so make it more common. You can shorten the lifespan of everyone else, maybe even due to the widespread use of the miracle pill--which worked like a dream, at first, and works even better if you take it during your reproductive years (if you don't suffer the side effects). But the next generation PAID for the years the older generation "stole." However much the span is lengthened for generation 1, if they take it before having kids, the next generation's life span may be severely shortened, with things getting back to normal generations later--MAYBE.

You can also make the pills addictive if taken over years, so that stopping taking them will result in all sorts of unpleasantness, ranging from pychotic behavior to death...

This is sci-fi, so you can play with the number of years you want to give and take!

• +1 for making the prolonging of the first generation's lives the very reason their offspring can't have long lives. I'd definitely go for the widespread adoption, not some legal restriction only on continued use. – Cyrus Mar 10 '17 at 15:00

## I told you all these years that microwaving food is bad for you!

Ok, so it might not have been microwaves. Maybe it was the GMO food, that hip new sugar-replacement, radiation from screens or some other new-fangled gizmo. Regardless, it turned out to have serious and irreversible side-effects on the health of those generations that were exposed to it from a young age.

It took more than 30-40 years for the first effects to show, and medical science is still busy tracking it down to the source, but the damage is done. People are deteriorating at younger ages and a 90 year lifespan is now out of reach for them.

If you want things to be even more grim, the change may be genetic and even children not exposed to the bad stuff still carry the damaged genes limiting their lifespans.

• Interesting idea. We can hit about 3 generations (G1 adopted the technology at around 10 years old, had kids at 20 (n+10 years), then G2 had kids at 20 (n+30 years) and then G3 had kids at 20 (n+50 years)). G1 is 60 by this time, and suddenly starts keeling over...but G0 is 80 or 90 by this point and probably won't live to see G2 die. – SPavel Mar 10 '17 at 14:46
• The deterioration may be quicker for the younger generations with increased adoption of the damaging tech/food/medicine. G2 might die at 45, G3 at 35. Still, without prolonging the lifespan of G0, you're not going to get much more without complete collapse of society – Cyrus Mar 10 '17 at 14:53

I suggest influenza.

The Spanish flu during World War I was notorious for killing the strong and young and shunning the elder people. A virus of that kind may emerge again, and set up the conditions for your story.

• Can the influenza persist over generations? The Spanish flu came and went pretty quickly. – SPavel Mar 10 '17 at 14:40

I suggest a disease like jknappen says. People could think a disease was extinct so no one past the long-living person's generation gets vaccinated and the disease suddenly strikes again (it wasn't extinct) which wipes out people really fast. Plus, the ingredients to make the vaccine are extinct (plants) or the vaccine doesn't work on the new people for some reason.

• If anyone has suggestions for a reason why the vaccine is gone please comment so I can edit my answer. – Noah Cristino Mar 10 '17 at 14:44
• There is a lot of people pushing agendas against vaccination. Yes, they are unreasonable, but if one of them get into a position of power... – T. Sar Mar 10 '17 at 14:57
• @TSar that's good for why they stopped but I want a reason to why they couldn't do it when people started dying. – Noah Cristino Mar 10 '17 at 15:07
• Civilization has collapsed and we are all subsistence farmers again. – Willk Mar 15 '17 at 18:29

After checking the world record of a Japanese women who celebrated her 106th birthday last year. We can say that a person can plausibly outlive a maximum of 4 generations

• Hello and welcome to WorldBuilding.SE! This looks like a valid answer, but we like more elaborate ones on this site. Could you flesh it out a bit? For example: could you add references for the average age of a generation and the oldest woman in Japan (you mentioned a world record) and explain your idea and the content of the references in a few more sentences/ paragraphs? I think this is sufficient, but more details would be very nice. If you got questions: ping with @Username, take the tour, visit the help center, come to meta and visit us in chat. Have fun! – Secespitus Mar 11 '17 at 15:33