Another way to look at this is to use the age at which skeletons begin to deteriorate. According to Ectocranial Suture Closure: A Revised Method for the Determination of Skeletal Age at Death Based on the Lateral-Anterior Sutures, the most common value found in age at bone loss is age 43. So, you could also say natural human lifespan is 43 years.
Or, if you want, here’s another scenario: If, during the human lifespan, skeletons are underdeveloped for 25 years before skeletal maturity, you could assume skeletons are no longer developed (in other words, they’re deteriorated) for 25 years after skeletal deterioration (the opposite of skeletal maturity) during the human lifespan, which begins, as I mentioned in my previous paragraph, at age 43. So if you add 25 years to 43 years, you get age 68, which, in this scenario, is the age you could use for the natural human lifespan.
Humans, in the wild, artificially prolonged their lives all the time. They took care of the sick instead of leaving them to die.
At any rate, you need to better define what you are asking. The average life span of a gorilla, I can assure you, is much less than 37 years. If you want to ask what is the oldest age a human could expect to live without modern medicine, then that’s a certain question that I don’t think anyone has addressed so far in this thread.
IOW, your OP is very ill defined. What specifically are you asking?
Just to repeat - Life Expectancy is a combination of the lives of those who die young and those who don’t. Life Expectancy goes up for civilized modern societies due to modern medicine, due to good nutrition being available through the full development of the individual - not just to forestall starvation, but good nutrition means healthy development, good immune system, etc. Better civilization means better public hygiene to offset the dangers of crowding that contribute to epidemic diseases. The ones that survive “in the wild” are just lucky, everyone has the potential to survive the same.
Finally, and probably most relevant to the OP’s question, is what result a lifetime of stresses puts on an individual. A lifetime of hard work or poor care of the body, continually stressed or exhausted, it seems will generally mean it is “worn out” before its time and not only look old be deteriorate faster.
FredOnEverything.com once commented on Mexican society that the young people looked the same as in the USA, while older people over 60 looked “like they’ve been carrying an anvil through the hot desert all their lives”. This is presumably the difference a civilization of plenty and less hard work make.
Here is a survival curve with information from england showing survival from age 0-100.
Before the 19th century (15-18th) the curve was pretty much the same. About 40% of people would die before age 15, then there would be a steady decline through the rest of life. About half of people made it to 40 (which isn’t bad, only 10% of people died between 15-40), 30% made it to 60, etc.
As medicine progressed the first 50 years survival is 95%+, then it starts to decline, then the decline becomes rapid. The % surviving to age 80 went from 5% in the 16th century up to 50% today.
But as everyone says, a lot of that death comes down to things like infectious diseases, accidents, a life of hard labor, physical trauma, etc.
A long time ago the number one killer of adult women (the 50-60% who didn’t die young) was childbirth, the number 2 was cooking over an open flame. Now deaths from infections or physical trauma is rare.
But again, lifespan hasn’t really increased much (if at all). I’d wager 5 years at the most. When the body craps out and stops working (which is what aging is) there isn’t much contemporary medicine can do.
Healthspan (which is something different) has seen some pretty big improvements. People live disability free and pain free for much longer than in the past.
Can’t we just look at the known human life expectancy before, say, 1800? Any “medicine” was random and usually did more harm than good. Add the savagery of a religious/church controlled life and you have a pretty good approximation for what “the wild” of living in a jungle was like. Nearly all meaningful advances have occurred in the last 150 years or so. I can’t imagine there’d be more than a year or two statistically significant difference between life expectancies from the 1500s versus 100,000 years ago.
Hmm… I have to disagree on that. Although what passed for medicine pre-1800 was spotty, the mere fact that over much of the world humans had either exterminated their main predators or driven them to the periphery, had developed food preservation techniques to moderate the feast/famine nature of food supplies, weapons to make hunting easier, agriculture in place of gathering, and collections of people that helped share the burden of work and also of caring for the less able members of society worked to decrease early death and increase lifespan. Civilization also allowed the survival of some individuals who would never have survived various insults both congenital and acquired.
Conversely, the resulting crowding resulted in more disease, which tended to the opposite effect.
The result is not a natural state at all leaving some question as to whether the result was either an increase or a decrease vs. the “natural state”, presumably hunter-gatherer.
I have come up with the correct way to come up with the correct answer. Reproduction is the reason we’re all here. So a fertile state is a human’s ideal state, a non-fertile state is not. However, it takes time for sperm cells and egg cells to mature. Just like it takes time for an apple to grow on a tree. This is why we are not fertile when we come out of our mother’s womb and into the world. But ideally, we should remain fertile until death. Ideally, both parents should be the same age as each other. According to tradition (by tradition, I mean the father of biology itself), the age that males start to get semen and females begin menarche is age 14. However, tradition states that most women go through menopause “in about their fortieth year” (and that men are “sexually competent until they are sixty years old”). Therefore, tradition holds that, it’s not possible for a 40 year old or older same age couple to conceive because of the woman’s infertility. So, with regards to same age couples, age 40 is when a human’s ideal state ends. In other words, we are biologically born to live 40 years, in ideal circumstances.
I’ve always been puzzled how so many of the founding fathers of the US lived such long lives. Adams and Jefferson both died July 4, 1826. Adams was 90 and Jefferson 83. George Washington died in 1799 at age 67. Ben Franklin was 84 when he died in 1790. James Madison lied till he was 85 and died 1836.
It’s astounding how they beat the odds and lived so long.
You’re thinking about it in the right way - it is about reproduction. But you’re missing all the data - reproduction is not just getting pregnant and bringing a child to birth. You have to ensure that child in its turn gets to reproduce.
Survival of the fittest isn’t just about survival of of the fittest individual. It is about survival of the fittest population. In the case of pre-civilization human beings, I think we are talking population in terms of a tribe. While there is a genetic limit to the span of human life, it is not matched to how long an individual is fit to reproduce. Rather, it is matched to how long an individual is of use to the tribe. Men and women who are past the age of conceiving a child themselves still have a role in passing on cultural knowledge to the younger members of the tribe. We aren’t born knowing how to make a stone axe, or to dig for nutritious roots. Certainly not how to build a nuclear reactor. It is not until there are other individuals able to pass on the cultural knowledge (think wisdom) to the younger generations, that someone becomes more of a burden than a benefit to the tribe.
Or, in an even less abstract way, if you die at 40 right after the birth of your last infant, that infant dies, as do any others under five, and likely any under 12. It’s not just about passing down cultural knowledge: it’s about providing food, shelter, and protection.
It’s not all that surprising. Obviously, they had all already lived to adulthood by the time they made their mark on history; they were also all men (no risk of dying in childbirth) and, except for Franklin, all from families that were comfortably well-off. (Adams’s family wasn’t wealthy, but his father was well-educated and a landowner; the others were definitely members of the elite.) So their chances of reaching old age were a lot higher than those of a randomly-selected infant in the Colonial era, and in fact, it would have been surprising if most of them hadn’t.
This is incorrect. Males of course potentially remain fertile well beyond the age of 40, essentially until death (although perhaps with reduced capacity).
It has been hypothesized (the Grandmother Hypothesis) that female menopause is actually an adaptation, in that at some point it becomes more beneficial to forego the risk of death in childbirth in order to be able to help care for your grandchildren.
With regard to humans in particular, evolutionary fitness is more than individual fitness. We are animals that live in family or social groups, and having older individuals with long memories around, even non-reproductive ones, can enhance the fitness of the group.
You are right, both are true. But, part of the benefit of communal living, as humans have done since prehistory, is that orphans get taken care of, although perhaps with reduced advantage than if both parents were still alive. So survival of parents until children reach adulthood is important, but perhaps not critical.
Four of the five men you mentioned were never in combat. George Washington saw combat in two separate wars and had to spend a great deal of time worrying about his personal survival which had to take its toll upon his health.
Even today you’d be hard pressed to find many vets who live much beyond the mean average, if they even make it to that point.
The concept of being genetically programmed to live until one is useless to a tribe is a hypothesis. I believe this is the grandmother hypothesis. But the fact is, a fertile state is a person’s ideal state. Because none of us would be here if people weren’t meant to be fertile. And ideally, the end of our lifespan should be when fertility is no longer possible. So, a woman gives birth to a child between around age 14-21, and dies at 40.
Evolutionary fitness is a theory. Yes, men are fertile past 40. But this is the way I’m treating this subject: I’m using an ideal situation where a would-be mother and father are the same age. And I’m considering the fertility of this couple as a whole (which makes it easier to select an age to mark the end of the human lifespan). Not separately for the man and woman. So fertility for the couple as a whole ends at 40.
But what about the children she gives birth to between 35-40? Is it really “fertility” if a chunk of your offspring die because you were not there to protect and provide for them?
You can’t draw evolutionary conclusions from a fabricated “ideal situation,” especially with one that is so far from the realities of human social behavior. Few primitive human cultures practiced pure monogamy. A degree of polygyny is common, where older and more successful males who control more resources can take younger, fertile wives. Even in cultures where polygyny is not practiced, older males often take younger wives. Add to this the fact that a significant number of births will be the result of unfaithfulness by partners. Your postulated conditions will not be typical.
