Just like the oft-perpetuated misinformation/misunderstanding about girls routinely marrying underage for most of human history, the belief that our ancestors were doomed to die at all of 35 is also a myth. It’s not that there’s no truth to it, but that it’s grounded in a lack of understanding of context.
Average lifespans have historically skewed so low because of high childhood mortality and childbirth death rates, and men dying in wars. If someone could get past all that, s/he stood as good of a chance as a modern person of making it into old age. People didn’t just drop dead as soon as they turned 35!
Let’s say there are two siblings. One, God forbid, dies of SIDS at three months, while the other lives to 95. Their average age is 47.
People with physically demanding jobs (e.g., coal miners, outdoor slaves, chimney sweeps) and from the lower socioeconomic classes, then as now, had much harder lives, and less access to the best doctors and medicine. They also didn’t have the option of taking off work to recover. However, even royalty and nobility fell victim to diseases and injuries in an era before modern medicine.
So what were the real averages and expectations?
If one survived to 15 in the Paleolithic Age, life expectancy was 34–54. In the Neolithic Age, it was 28–33. Our prehistoric ancestors lived short, hard, brutal lives, long before modern medicine. They were at the mercy of the elements, enemy tribes, wild beasts, diseases, and injuries.
However, we’ve found bones of Neanderthals and Cro-Magnons who survived into old age. Some survived multiple traumatic injuries, missing teeth, and arthritis. Their clanspeople continued to take care of them, chewing or grinding their food for them and carrying them from place to place.
Bronze and Iron Ages:
If one survived to 15, one could expect to live to 28–33. While our ancestors no longer lived in caves by this point, and had the advantage of cities and farms, life was still harsh. However, as with all other historic lifespan averages, it’s consistently 70–80 once childhood mortality is removed. The longer one survived, the more likely old age was.
At 15, one could expect to survive to 37–41, though there were many elders. Socrates, for example, died at 70, from poisoning. Had he not angered the authorities, he may have lived at least another decade.
If one lived to 20, life expectancy was 50–60. Many Romans lived into old age, and enjoyed a great quality of life. Cato the Elder lived to 85.
Golden Age of Islam:
Scholars lived from 59–84.
The Bubonic Plague skewed life expectancy to 45, but if a man survived till 21, he could expect to live into at least his sixties. Given the dangers of childbirth, it was somewhat lower for women, but there were more than a few female elders. It’s a total myth that no one bathed in the Middle Ages, everyone lived in filth, and peasants lived lives full of nonstop exploitation.
It’s much the same through the Renaissance and 17th, 18th, 19th, and early 20th centuries. There were many people in their eighties and nineties; e.g., Benjamin Franklin, John Adams, Thomas Hobbes, Thomas Jefferson, King Eric of Scandinavia, Michelangelo.
Handling longevity in your writing:
Having historical characters dying in their thirties, absent any diseases or injuries, does a great disservice to true statistics. On the flip side, it’s equally unrealistic to have all your characters living past 100.
I like to save extreme longevity for a family matriarch or patriarch, someone really special, or a storyline about how old age can be very lonely and depressing, more curse than blessing. My character Cinnimin lives to 120, to show her going through twelve decades of history and spawning all these succeeding generations.
The oldest person whose age has been verified was Jeanne Calment, age 122.