Synopsis: We’ve made the 1st giant life expectancy leap, and the 2nd is looming.
Increased life expectancy and the ageing population of today is not yet a result of the next step of modern medicine providing treatment to slow aging or increase the length of a full lifespan of a healthy person, but by the reduction of infant mortality and the probability of a person enjoying their full potential healthy lifespan.
This video by Neil de Grass Tyson is a whimsical tale, but the “we can expect to live twice as long today as people in the year 1900” is quoting a statistic almost as misleading as “on average, adult humans have approximately one breast”. An average of two separate groups represents neither group, which is why almost no one born in 1900 died at the age suggested by life expectancy. There were two groups, with around 50% who died very young, and the other around 50% who mostly died at age not so different from lifespans of today.
Consider the IMDB list of people born between 1900 and 1910, and it is clear that the life expectancy does not seem to be only half of what it is today. The reason the data is biased, is the people who died as children rarely achieve fame, and at that time, a lot of people died as children, which is why the average is so low.
Historically, there are two points in the lives of humans when they are most vulnerable, one in the first few years of life, and then again another when approaching the end. This made two groups within the statistics with both groups far from that average. Those who died as children, and those who became adults and had life expectancies more similar to people today.
The first big change to extended life expectancy from 32 years to over 70 years during 20th century and came near to elimination of that first vulnerability of childhood mortality which moved people from the group dying as young children to the second group who mostly get far closer to a full lifespan. Although it has had as smaller impact, vulnerability in the second group has also been reduced, bringing more people closer and closer to achieving their full lifespan. The next big change would be extending that lifespan and although so far there is no medical intervention or treatment stop ageing or extend the possible lifespan, one could, and probably will, arrive one day.
The terminology of life expectancy is explained below, as is the importance of the contribution of the reduction of child mortality through the history modern medicine enabling extending life-expectancy.
Graphs of life expectancy has increased should not be mistaken as people living longer or an increasing of the human full lifespan, but instead as graphs showing the elimination of young people dying so that an ever-increasing percentage of people experience their full potential lifespan.
The impact has transformed the human experience far more than would have resulted from longer lives for all, as it has eliminated the tragedy of nearly all parents experience the death of half of their children at a young age.
But this change also has brought challenges of a population explosion that could yet result in disaster that has so far, amazingly, seems to have been narrowly avoided. So far, humanity has risen to the challenge of supporting this massive increase in population but so far only by when living unsustainably which effectively means borrowing from our own future generations. It may seem medicine now has less to contribute as we head towards at peak child and hopefully progressing towards sustainability and population stability, but it is just too tempting to avoid trying a second step: the extension of the human lifespan.
The next step, which may be needed to properly further the current step of reducing early deaths, is to learn why our bodies progressively worse at producing the cells we need. Either solve this next step, or even make significant steps to solving this next step, and we could not only cure cancer and other conditions, but we could also enable people to live for 200 years, 300 years, or even indefinitely.
However, while we created a problem during the industrial age of where to put and how to feed the population explosion that resulted for the reduction of child mortality, it is a far simpler problem than the one raised by solving “elderly mortality”.
Having continued to extend life expectancy for centuries, why would we stop now? But, there seems little point in extending life expectancy very much further, unless we can eliminate or delay ageing.
If we could eliminate ageing, and I believe it is possible and if society survives will gradually happen, then either we restrict births to matching deaths by misadventure, or we find a way to handle yet another population explosion. As a result of the Sun progressing through its cycle making the Earth unable to support human life in as little as 25 million years from now, humans were always going to need to find a new home.
If we do significantly reduce “elderly mortality“, we need to find maybe not a new home, but at least some space-cities in far, far less than 25 million years. My theory is that at least reducing elderly mortality is our future and, in many ways, a promising future even if it brings the timescale for needing additional colonies down from 25 million years, to around 500 years. Maybe this is why the billionaires are checking the exits?
Implications of reducing elderly mortality.
Some terminology often confuses and could require explanation.
Average lifespan vs life expectancy vs full lifespan.
Average lifespan for a population can be calculated by recording the age at death of each individual, and once the last person has died, calculating the average. Consider a small hypothetical group of 10, where 2 died as an infant (before the age of 1), another as a 10-year-old, another as an 18-year-old teenager, another at 40, two at 60 and remaining 3 lived into retirement and died on average that age of 70. It could be said that for this group:
- average lifespan = 2×0 + 10 + 18 + 40 + 2×60 + (3×70) = 39.8 years.
- full lifespan = 70
- life expectancy was 39.8 years.
Average lifespan is simple, add up individual lifespans and divide by population size. The problem is you need to wait until everyone in that population dies to have a statistic that will represent the life expectancy that applied for that group.
Life expectancy.
Life expectancy is simply a method for being able to predict average lifespan.
What is required is historical census data that includes age at time for a population over a period of one full lifetime or longer. The statistical outcomes for each group can then be tracked. For example, comparing 10-year-olds today with births 10 years ago would provide a survival rate, if only people would just remain in the area covered by the census and not move in or out!
Despite the challenges, survival rates to each age do get calculated and then used to calculate a snapshot average lifespan for any given year, even though at any point in time survival rates for 10-year-olds will be from those born 10 years ago and survival rates for 60-year-olds will be from those born 60 years ago.
The fact that if there is population growth, the 10-year-olds will have begun as a bigger group than the 60-year-olds, is easily adjust for by using the census data of births 10 and 60 years ago. A twist is that the 60-year-olds may have had a different survival rate when 10 than today’s 10-year-olds, which means if there was a difference, then composite life-expectancy build from all ages would show different overall survival until 60 rates for today than those born 60 years ago experienced.
Perhaps surprisingly, life expectancy normally increases until you die.
If you are reading this, you have a higher life expectancy than what current data seems to suggest, unless you have found life expectancy data specifically for people at your age.
If you can read this, you would certainly be aged 1 or higher, and very likely 10 or higher, so….. good news!
With the same data, life expectancy increases at every age, because for every age, life expectancy is then the number only for those who already survived thus far. In society with high infant mortality, 5-year-olds can even have a higher expectancy from age 5 than they had at birth.
Consider a small hypothetical group of 10, where 2 died as an infant (before the age of 1), another as a 10-year-old, another as an 18-year-old teenager, another at 40, two at 60 and remaining 3 lived into retirement and died on average that age of 70.
Average lifespan vs life expectancy vs full lifespan.
The average life expectancy at birth for this group is 49.8 years but consider the average only for those who their first birthday: it is 62 years! If you reach your first birthday you know you are now one of the 80% with on average another 61 years to live, and thus life expectancy at age 1 jumps to 62 years. Further, if you reach 60, it does not mean you only have 2 years to live, as you have entered the group who reach age 61, and that group has on average 5 years to live. Due to the ever-smaller sample group data gets too imprecise, and once you reach the age of 70, you have lived as long as anyone in that small history, and there is no more data, however even that does not mean you will die immediately.
‘Full lifespan’, or just ‘lifespan’ is calculated by considering in the only the people deemed to die of age-related causes as often labelled ‘old age’. From the group “average-lifespan” above, this excludes those who died as a baby, a 10-year-old, and an 18-year-old, as well four others who would be considered to have ‘died young’. In a sense, it is the age a person will live if it could be said “nothing goes wrong”. Unlike average lifespan, with a simple formula, and life expectancy with a more complex formula, a value judgement is required to in borderline cases arbitrarily allocate deaths as ‘age related’ or not, making ‘full lifespan’ an inexact value. As a concept I feel it is very important, but we have no scientific exact number.
The traps and surprises.
A trap is that we often think ‘life expectancy’ as reflecting ‘full lifespan’, but the two numbers will only even be close when only very few people ‘die young’. Confusing these two terms or and miss interpreting life expectancy numbers can lead to surprising differences between reality and what we would think is/was is being reflected by the numbers.
Another trap is that while life-expectancy can be calculated from any starting age, when an age is not specified, the number is the “life-expectancy at birth”.
Ageing population: An inevitable result of the reduction in child mortality.
Two factors driven the reduced mortality rates, and primary reduced child mortality rates, have resulted in modern society having a much older average age than pre-industrial societies.
Prior to 1800, on average families had 7 children, provided both parents completed their childbearing years. Of course, some had far more, and some had none. Of those 7 children, on average 25% of children in their first year, and another 25% died during the rest of their childhood, leaving approximately 3.5 children to have their own families [Gapminder, verywellhealth]. These childhood deaths being the biggest factor in the global average life expectancy of 30 years. With a life expectancy of 30 years, everyone living past 30 increases the average, those dying before 30 lower the average. On average that should leave around half of the children to potentially have their own families, but population history reveals population growth data reveals population, especially prior to 1650 CE, was too slow for even on average 3 children per couple to manage to have their own children.
The main factor creating an “ageing population” is the reduction of childhood mortality that was keeping life expectancy low. A secondary factor but less significant factor is the reduction in the number of children that follows the increased survival rate, and the third factor and least significant factor of all is the delaying of deaths of older people.
Life expectancy changes are mostly due to child mortality.
In some ways, life expectancy has not changed all that much from 1800 to what it is today. Setting aside infant and child mortality, the average lifespan for women and men of the mid-Victorian era was 73 and 75 respectively.1 By comparison, in 2021, the average life expectancy for females in the United States was 79 while the average life expectancy for males was 73.2
Even when you step back in time, changes in life expectancy were not always as dramatic as one might expect. Depending on which study you refer to, there are records of populations living well into their 50s in ancient Rome and their 60s during the late Renaissance.1
Life Expectancy From Prehistory to 1800 and Beyond
How child mortality has changed.
Looking at historical data, where, despite the average life expectancy being around 30, Plato lived until 80 and almost everyone who was famous but not assassinated or something lived until at least 60, it at first looks like the numbers just do not add up.
But then you realise, historically, at least 2 thirds of children born died before reaching adulthood. Dying in childhood would usually mean the person never became famous, especially considering that, of those who died, a significant proportion died as infants in their first year.
Throughout human history up until the 20th century, the age when people are statistically at the greatest risk of death for a human being was the during their first twelve months whilst still aged 0 years old. Even today there is still a risk of death as high as 10% in the first year for those in such countries as Afghanistan today (see chart from CIA factbook), highlighting the critical role of medical care in humans surviving even to their first birthday.
The risk of childhood death does not end at age one and historically nearly half of all humans died as children, and thus never lived to have their own children.
The impact of child mortality on life-expectancy.
It is the death of young people that has the greatest impact on life expectancy because dying just a few years earlier has little impact the statistics.
Consider the hypothetical group of 10 people from the section on average lifespans.
Consider a small hypothetical group of 10, where 2 died as an infant (before the age of 1), another as a 10-year-old, another as an 18-year-old teenager, another at 40, two at 60 and remaining 3 lived into retirement and died on average that age of 70.
Average lifespan vs life expectancy vs full lifespan.
Living in a society where a medical intervention could extend the two lives of people who died at 60 to the full 70-year lifespan would lift the group life expectancy by 2 years to nearly 52 years.
However, in a society where a medical intervention could save the lives of the two infants and extend their life to the 62 years average lifespan of those who live past their 1st birthday would lift the group life expectancy by 12 years to 62 years.
In this case, if society that finds a solution to those deaths at 60 it will life expectancy by 2 years, but a solution to the cause of infant deaths lifts life expectancy of the society by 12 years.
While it is mostly child mortality, there is more.
The large reduction in child mortality has played an important role in increasing life expectancy. But life expectancy has increased at all ages. Infants, children, adults, and the elderly are all less likely to die than in the past, and death is being delayed.
This remarkable shift results from advances in medicine, public health, and living standards. Along with it, many predictions of the ‘limit’ of life expectancy have been broken.
Our world in data: Life Expectancy
History: Full lifespans have not changed over a long time.
Past lifespans: similar to today and partly a misunderstanding.
The big change is not to how long old people lived, but a change to how many died as babies or children.
I watched a discussion on the prospect of research enabling people to live longer, and I was disappointed the discussion was somewhat derailed by myths and of misunderstandings of history, from misinterpreting ‘life expectancy’ as representing ‘full lifespan’. A proper discussion requires understanding the difference between increasing life-expectancy by increasing the percentage who reach their full lifespan, and the so far not achieved increase by increasing full-lifespan itself.
But it was not until I took a deeper look, that it became clear how different the past was from what I imagined.
A did a search on random figures from the past, and found: Galileo born in 1654, died at 77, Newton born in 1727 died at 84 and Darwin born after 1800 in 1809 died just a little younger at 73.
Yes Mozart famously died at 30, but was poisoned. What about ancient Greeks? Pythagoras lived to around age 75, back 500 years BCE! Socrates? Lived to around 71. Plato? 80. Aristotle? 60..61! Finally someone died a little younger, Ramesses lived to 90 and it becomes very clear that historically even 2,000 years ago when life expectancies were so much shorter, that did not mean that it was typical to die as a young adult. Many people lived to an age not that much less than we consider a typical today.
Anyone checking their own ancestry will find their ancestors from 1900 typically well outlived that global average of just over 30 at the time, but of course, relatives from the time that died as babies are not their ancestors.
Further evidence comes from societies long isolated from the rest of the world, such as the indigenous Australians. It is clear that prior to contact with Europeans, tribal elders could also live to an age of 70, and even an age of 100.
When you think about it, despite the life expectancy in early 20th century being little over 50 even in the best locations, we have people born at that time over the age of 110. Indigenous Australians are genetically very similar to Europeans and evidence is that genetics have not changed much in at least 30,000 years. This means humans even 30,000 years ago were genetically capable of living until at least around 70, even if the harsh living conditions at that time made such a full lifespan uncommon.
The 20th Century.
The data accepted as being the global picture, is that:
In 1900, the average life expectancy of a newborn was 32 years. By 2021 this had more than doubled to 71 years.
Our world in data: Life Expectancy
However, in 1900 and early 20th century, life-expectancy was no homogenous across the globe, nor was the accuracy or extend of data, so data for specific regions will be quite different.
Data can be misleading and where data is from can have quite an impact. According to this US data, in the USA in 1920 the life expectancy was just 56.4, which also seems low given now in 2022, there are millions of people in the US now over the age of 102, who were all born 102 years ago in 1920, and so almost doubled that life expectancy. Whilst infant mortality plays a huge role, it also appears that even within the USA data was not homogenous.
Note that as of 2022 that same data as used for 1920 figures shows that in the USA during 20th century, that life expectancy rose from 49.2 to 80.3 years,
Data from prior the 20th century.
We don’t have accurate records of life expectancy prior to the recording of census data, but 30 years is widely accepted the global historical numbers, as shown on the graph from world in data.
From the 1500s till around 1800, life expectancy in Europe varied but hovered between 30 and 40 years of age:
From the 1500s until around the early-1800s, life expectancy throughout Europe hovered between 30 and 40 years. This was due in part to infant mortality rates that remained at 25% until 1800.
Life Expectancy From Prehistory to 1800 and Beyond
Note the 25% is infant mortality, which is those not yet 1 year old, and was around half of all childhood mortality, which in total was around 50%.
In some ways, life expectancy has not changed all that much from 1800 to what it is today. Setting aside infant and child mortality, the average lifespan for women and men of the mid-Victorian era was 73 and 75 respectively.1 By comparison, in 2021, the average life expectancy for females in the United States was 79 while the average life expectancy for males was 73.2
Life Expectancy From Prehistory to 1800 and Beyond
Again, data for Europe would differ from other parts of the world.
Historically, humans did not only live until 30 years of age.
Well….yes, they for most of history is it likely that life expectancy was only 30, and thus this was the average lifetime, but just as the average roll of a dice is 3.5 but you could still roll a six, the average outcome from the subset who survived childhood and lived to become adults, would have been more like living until 50 or more. Consider chimpanzees who have a life expectancy in the wild of just 15 years, but those who live past 12, typically live then until close to age 30. We believe just take those numbers and approximately double them, and you get the picture for ancient humans.
Life expectancy estimates for ancient and pre-industrial times also suffer from not only a lack of reliable evidence but also how the evidence is interpreted. This is because life expectancy to many suggests how long a person will live as opposed to how long they can live.
And, this is a misconception given that many people in ancient and pre-industrial times lived just as long (and sometimes longer) than many adults living today.
Life Expectancy From Prehistory to 1800 and Beyond
What about pre-history and before 30,000 years ago?
While the evidence is unambiguous that up until around 30,000 years ago, a full human lifespan was similar to a human today. Prior to 30,000 years ago, although I have not seen convincing evidence, there are some reports that report humans really did sometime prior to 30,000 years ago have a shorter lifespan more similar to chimpanzees today with their 15-year life expectancy and 30-year lifespan.
I will collect any data supporting this in this section, and this paper makes no assumptions about human lifespan prior to 30,000 years ago.
I sometimes encounter statements of how primitive humans had a life of expectancy of only 30 years, so they had to have children very young, in order to be able to raise them before they died. If this was ever the case, then it relates to genetically different humans, who would have had a life expectancy similar to chimpanzees.
I believe these statements are misguided and suspect by the time one of these paleolithic humans was a parent, and had already survived their child period of danger, their life expectancy at that time would have been to at least 40 and even if genetically somewhat different to today would have a potential lifespan of at the very least around 50 years of age. However, under the conditions of the time, achieving that full lifespan could have been rare. The reports I have seen only reference research without quoting that research, leading me to be unsure whether the original research is quoting life expectancy of humans with a reduced lifespan, which is very possible, but how reduced I am unsure.
If people were equally likely to die at all ages of a 60-year lifespan, the average age at death would be 30 there would be an even spread of people dying at ever age from 0 as at 60. Reality is, humans are most vulnerable as infants and when older, so most ancient humans would have died as a young child or a grandparent, unless they met with misadventure in battle or were otherwise unlucky. However, there are reports of a lack of remains of “the elderly” in Paleolithic times. Did they have a bad diet or something?
We conclude that the increase in adult survivorship associated with the Upper Paleolithic is not a biological attribute of modern humans, but reflects important cultural adaptations promoting the demographic and material representations of modernity. Am J Phys Anthropol, 2006. © 2005 Wiley-Liss, Inc.
Is human longevity a consequence of cultural change or modern biology? – Caspari – 2006 – American Journal of Physical Anthropology – Wiley Online Library
To be researched: Exfoliation of deciduous teeth and gingival emergence of permanent teeth in Australian Aborigines
Humans are still humans.
And if you’re in suspense, yes, they’ve also pinned down important events in our evolutionary timeline. Everyone alive today seems to share ancestors with each other just over 200,000 years ago and with Neanderthals between 765,000-550,000 years ago.
Why we’re closer than ever to a timeline for human evolution
Common ancestors aside, it is possible that, go back far enough, and the genetic mix was different, but even indigenous Australians who date back as a group at least over 50,000 years, who were basically isolated from other humans for at least 12,000 years, are still basically genetically the same as Europeans and given similar opportunities experience the same life expectancy. Of course, statistically too many do not experience to same opportunity and therefore not quite the same life expectancy, although still far beyond anyone of even 1900, which further supports that this not some genetic difference.
At least in the most recent 30,000 years, human genes have not changed significantly, and ancient people tended to get exercise and stay clear of junk foods excessive alcohol and smoking. Even if the lack of any medical care meant most died as children, once clear of childhood, there was a reasonable lifespan ahead, just as there is in indigenous groups still living traditional lifestyles today.
What is the next step for extending life expectancy?
We have not finished but are close to the limit on eliminating early deaths.
Although some people do live until and even beyond the age of 100, we currently lose health rapidly from around 70 years of age and the qualify of life diminishes from that point. Yet many in many countries, life expectancy already exceeds 80 years. There is, tragically, still too many early deaths that we would hope medicine will in future be able to prevent, but life expectancy is getting close to the level of a full lifespan under current conditions.
Despite wishful claims that the ’40 is the new 30′, and ’50 is the new 40′, this is more about more people retaining their full health longer, than a breakthrough leading to people aging slower. Mostly it has been habits undoing the harm from recent backward steps in terms of diet, smoking and lack of exercise. A person who does not suffer accident or disease, now lives about as long as our rate of aging allows. There seems little point in being kept alive much longer if health continues to decline through aging, and while that is the next step, we are not there yet.
There is still cancer and many other barriers to a full lifespan.
Although statistically the rise from 32 years to as high as 80 years could be seen as more than double and a rise on average of from 32% to 80% of a full lifespan, it is not so simple. Even those percentages are misleading, as 90 years seems even more than a full lifespan for most while others manage well over 100, taking up the average and perhaps making appearances better than reality. More significantly, actual lifespans still vary right throughout the range from 0% to 100% with the tragedy of early death still although less common, just as real for far too many.
Of course, there is the drive to go further and cure many other so far incurable conditions, but as we progress in that direction solutions can overlap with another path as unlocking the mysteries of disease and how biology works to solve these problems opens the door to: could we end or delay aging itself?
Elderly mortality: But we have barely started on ending ageing.
The very nature of some of the causes of early death are very much like the problem of ageing itself in that there is a failure of cells to reproduce perfect examples of the cells our bodies should have.
The next step, and one that has not really advanced much yet, is to tackle aging itself.
Living in a world where everyone ages, aging seems both natural and unavoidable, but this is not necessarily the case. Consider:
- Single cell organisms never age.
- It is also possible for multicellular plants and animals to live forever.
- Every human ever, over hundreds of thousands of years, is made from cells made by previous humans, resulting in a long chain of effective immortality.
- The cells in our bodies range from a few hours old through to decades, meaning we are constantly being renewed, and can be much older than our own cells.
- Our DNA effectively runs a timer, deliberately limiting our lifespan.
Search “aging as a disease” and you will yield multiple results confirming that aging itself could be seen as a potentially curable disease. Or at least a disease that where the effects could be delayed.
Most people accept that getting old is an inevitable part of life. We are born; we grow to become fertile adults, and then our bodies age until they expire at an average age of 80 for men and 84 for women in British Columbia. As we age, some of the inevitable symptoms include graying and thinning hair, loss of fertility, weakening bones, decreased brain function and losing our ability to hear and focus our eyes. But why does this happen? Why don’t our tissues continue regenerating forever?
None of us are spared from physical aging, however single celled organisms do not age as we do. Amoebas and bacterium will live for a time and then split into two daughter cells without deteriorating. These single celled organisms never lose the ability to proliferate. On the other hand, human cells only have the ability to divide about 50 times before dying.
Born to die: Why do humans get old?
Implications of reducing elderly mortality.
Just as reducing child mortality not only increased life expectancy but triggered a population explosion, a significant reduction of elderly mortality would have very similar effects.
If we do significantly reduce “elderly mortality“, we need to find maybe not a new home, but at least some space-cities in far, far less than 25 million years. My theory is that at least reducing elderly mortality is our future and, in many ways, a promising future even if it brings the timescale for needing additional colonies down from 25 million years, to around 500 years. Maybe this is why the billionaires are checking the exits?
Summary.
There are a few key points:
- Improvements in life expectancy so far have predominantly resulted from eliminating causes of early deaths rather than extending the overall biological clock.
- Shorter life expectancies as low as 30 years from the past, result from the average age being much shorter, mostly due to infant and child mortality resulting in many very short lives significantly lowering the overall average.
- The human biological clock still runs at very much the same speed it always has, and life expectancy is now close to the limits of that clock.
- Further significant increases in life expectancy can only result from slowing, or even stopping, the biological clock, which does appear, at least in theory, possible.
Updates.
- 2024 Feb 10 th: Updated synopsis and added elderly mortality.
- 2022 May 20: Started discussion on further increase in life expectancy.
Planned: More discussion is needed on extending life expectancy.