Amid revolutionary advances in medical science, researchers around the globe are currently debating the maximum age possible for humans and asking: is there a biological limit? Will medical advances push that limit beyond what is now thought possible?
The number of people living past 100 is steadily increasing. Worldwide around 500,000 people are currently aged over 100 – with a small group of ‘supercentenarians’ over 110.
Official records list the oldest person to have lived to date as Jeanna Calmet in France, who died in 1997 at 122 years and 164 days.
One of the most spirited debates in science today involves how long people can live, whether resources should be directed toward ‘life extension’ versus ‘health ‘extension’, and what is standing in the way of rapid progress towards slowing the biological process of ageing?
At the centre of these debates are two fundamental questions:
- Is there a limit to human longevity?
- And, if there is one, are we close to it?
A new 2021 study by researchers at the University of Washington has analysed data from over 1,100 ‘supercentenarians’ in the International Database of Longevity – a resource that only includes people whose age can be confirmed with a high degree of certainty.
The researchers concluded that this century (by 2100):
- it is nearly certain someone will live longer than Calmet’s 122;
- but it is highly unlikely anyone will live to 135.
The scientists reported that while longevity may continue to rise slowly by the end of this century – and statistical modelling examining the extremes of human life shows a life span of 130 years may be attained – the ‘probabilities that a person lives to at least age 126, 128 or 130 this century are 89%, 44% and 13%’. (See box 1.)
The authors point out that, even with population growth and advances in healthcare, the mortality rate will continue to flatten after a certain age – so someone who lives to 110 has about the same probability of living another year as someone who lives to 114.
Study co-author Professor Adrian Raftery explained that once people reach 110, they still die at the same rate, and medicalnewstoday.com commented: ‘Even though the model used in this study suggests the maximum reported age at death will continue to increase, the frequency at which this record is broken will decrease unless the number of supercentenarians grows significantly.
‘With a continually expanding global population, researchers believe this growth is a possibility.’
Professor Raftery noted: ‘This is a very select group of very robust people. They’ve gotten past all the various things life throws at you, such as disease. They die for reasons that are somewhat independent of what affects younger people.’
This latest US study followed similar findings in a landmark Swedish study which examined the question: Does the human lifespan have an impenetrable biological upper limit which will stop further increase in life limits?
It analysed populations in Western countries and Japan, and reported that ‘given the present state of biotechnology, it is unlikely that during the next 25 years anyone will live longer than 128 years in these countries’.
Interestingly, those scientists also noted no difference in mortality after age 110 between sexes. (See box 2.)
Differing scientific opinions
In the current debate, many scientists and researchers ‘disagree on the plasticity of old-age mortality’, summed up medicalnewstoday.com.
Some forecast a fixed limit to human lifespan ‘based on biological forces, such as the inevitable deterioration of cells’.
For example, a joint study by scientists from the University of Illinois, University of Oklahoma and France’s Institut National d’Etudes Demographiques – which examined data from France, Japan and the USA – concluded: ‘Given the presence of entropy (the degree of disorder or randomness) in the life table, a life expectancy at birth of 100 years, if it ever occurs, is unlikely to arise until well past the time when everyone alive (at the start of the 21st century) has already died.’ (See box 3.)
In a recent update to that study, titled ‘Inconvenient Truths About Human Longevity’, the scientists noted that while the rise in human longevity ‘is one of humanity’s crowning achievement’ – and although advances in public health beginning in the 19th century initiated the rise in life expectancy – recent gains have been achieved by reducing death rates at middle and older ages.
The ‘Inconvenient Truths’ researchers noted intense debate about the future course of life expectancy has been ongoing for the last quarter century and summed up: ‘Some scientists suggest historical trends in longevity will continue and radical life extension is either visible on the near horizon or it has already arrived; whereas others suggest there are biologically-based limits to duration of life, and those limits are being approached now.’
In their latest study, they lay out the line of reasoning and evidence for:
- why there are limits to human longevity;
- why predictions of radical life extension are unlikely to be forthcoming;
- why ‘health extension’ should supplant ‘life extension’ as the primary goal of medicine and public health; and
- why promoting advances in ageing biology may allow humanity to break through biological barriers that influence both lifespan and healthspan, allowing a welcome extension of the period of healthy life, a compression of morbidity, but only a marginal further increase in life expectancy.
The authors note that during the 20th century, life expectancy at birth rose by an unprecedented 30 years – faster than at any time in recorded history – because infant and child mortality ‘dropped precipitously in the first half of the century due to advances in public health’.
This ‘powerful force that brought forth the first longevity evolution and a rapid 30-year increase in life expectancy at birth, cannot happen again’. (See box 4.)
Biological determinants of ageing
According to the World Health Organisation, between 2000 and 2050 the proportion of the world’s population over 60 years will double from 11% to 22%.
Accompanying the 21st century’s far-reaching advances in medical science, Stanford University’s Professor Leonard Hayflick has noted: ‘The belief that ageing is still an unsolved problem in biology is no longer true.’
In a study published in the journal Science – similarly forecasting (as noted above) a fixed limit to human lifespan ‘based on biological forces, such as the inevitable deterioration of cells’ – he explained the four phenomena that characterise the finitude of life are ageing, the determinants of longevity, age-associated diseases and death.
Professor Hayflick noted there are only two ways age changes can occur: either as the result of a purposeful program driven by genes, or by events that are not guided by a program but are stochastic or random, accidental events.
He emphasised: ‘The weight of evidence indicates that genes do not drive the ageing process, but the general loss of molecular fidelity does. Potential longevity is determined by the energetics of all molecules present at and after the time of reproductive maturation.’ (See box 5.)
Previous ‘limits’ no barrier
Other scientists have argued that mortality for people in their 80s and 90s has decreased significantly in recent years and ‘proposed caps to human lifespan have always been broken within an average of five years after they were suggested’, noted medicalnewstoday.com.
For example, in a study titled ‘Broken Limits to Life Expectancy’, UK Cambridge University Professor Jim Oeppen and Professor James Vaupel from Germany’s Max Planck Institute For Demographic Research noted that for 160 years prior to the start of the 21st century best- performance life expectancy steadily increased by a quarter of a year per year, ‘an extraordinary constancy of human achievement’.
They declared: ‘Mortaility experts have repeatedly asserted that life expectancy is close to an ultimate ceiling; these experts have repeatedly been proven wrong.
‘The apparent leveling-off of life expectancy in various countries is an artifact of laggards catching up and leaders falling behind.’
What both sides of the ‘limited-unlimited’ human lifespan argument have in common is uncertainty – with unknown future scientific breakthroughs, and current lack of detailed knowledge regarding the mechanisms of ageing, preventing definitive conclusions.
Beware mathematical reasoning
A scientific ‘Law of Mortality’ was first proposed by British mathematician Benjamin Gompertz in 1825; it rested on the assumption that a person’s resistance to death decreases as his/her years increase.
The model was a refinement of a demographic model devised by fellow English scholar Robert Malthus, used by insurance companies to calculate the cost of life insurance. (See box 6.)
In warning against the ‘mathematical line of reasoning’ in some recent studies, ‘suggesting that survival time can be manufactured indefinitely by hypothetical medical technologies that do not yet exist’, the authors of ‘Inconvenient Truth’ (noted above) declared: ‘Although it may seem odd to use a purely mathematical line of reasoning to formulate a hypothesis about a fundamentally biological phenomenon such as human longevity, in the field of ageing this is common because duration of life is often studied by scientists that work exclusively with mortality statistics, without considering the biology that drives the phenomenon being observed.’
The authors explain that, although there is no reason to believe there are specific biologically-based constraints on running the mile or skating 1,000 metres or the distance a javelin can be thrown, the basic design of the human body ‘nevertheless imposes indirectly determined limits on strength, speed and duration of life’ – including ‘the Achilles heel of an ageing brain’.
The fact is, humans cannot run as fast as a cheetah, jump as high as a gazelle or live as long as a Greenland shark (392 +/- 120 years) ‘because the body design of each species, which is based on a genetically-determined set of life history attributes that evolved over millions of years, are not optimised with longevity as the end game’.
The authors note ageing as we know it is the ‘unintended consequence of accumulated damage (coupled with imperfect repair mechanisms) to the same human biology that also gives us life.
‘Human longevity should best be thought of as an inadvertent by-product of fixed genetic programs that optimise for growth, development, reproduction and ensuring the reproductive success of offspring.
An ‘intrinsic mortality signature’
Explaining why cures for major fatal diseases today will no longer produce large increases in life expectancy, researchers have hypothesised that almost all sexually reproducing species possess ‘an intrinsic mortality signature’ (a schedule of age-specific death rate) that is linked specifically to the reproductive schedule inherited by each species.
These mortality schedules should reveal a common mortality pattern and a predicted maximum life span for each species.
In a detailed study of this hypothesis, US Professors Jay Olshansky and Bruce Cranes concluded in a 2013 study that the life expectancy limit for humans was approximately 85 years at birth. (See box 6.)
Bodies have ‘biological warranty periods’
Some scientists studying potential age limits accept an ‘evolutionary conclusion’ that bodies have ‘biological warranty periods’ – and the expiration date of those warranty periods is linked to the time required to reach sexual maturity, reproduce, nurture young and (for some species) provide grandparenting.
While there may be no genetically- driven program for ageing or death, there are biologically- based limits on human longevity which are ‘driven by fixed genetic programs that influence human body design’.
An inadvertent by-product of these programs is limits on multiple functional attributes of the species – and longevity is one among many; hence the Olshansky-Carnes conclusion (noted above) that age 85 represents an average upper limit to life expectancy at birth for humans.
However, this 85-years life expectancy limit is for a population, which means:
- approximately 40% of the original birth cohort must live to at least age 90;
- 5-6% are likely to reach 100;
- a small percentage of the cohort is expected to reach ages 110- 115;
- exceeding 115 is likely to occur for only a handful of people.
This model was corroborated by US biochemists Dr Xiao Dong, Dr Brando Milholland and Dr Jan Vijg at New York’s Albert Einstein College of Medicine in their 2016 study ‘Evidence for a limit to human lifespan’ published in the leading journal Nature. They set out to test the theory that ‘longevity may not be subject to strict, species-specific genetic constraints’.
But they concluded: ‘By analysing global demographic data, we show that improvements in survival with age tend to decline after age 100, and that age at death of the world’s oldest person has not increased since the 1990s.
‘Our results strongly suggest that the maximum lifespan of humans is fixed and subject to natural constraints.’
Similar findings – that the rise in life expectancy in developed nations has decelerated in recent decades and has begun to level off just short of 85 in many of today’s developed nations – were reported by US Professors Anne Case and Angus Deaton from Princeton University in their 2015 study ‘Rising morbidity and mortality among white non- Hispanic Americans in the 21st century’ published in the journal PNAS. While the past century was a period of increasing life expectancy throughout the age range which resulted in more people living to old age and spending more years at older ages, University of Southern California’s Dr Eileen Crimmins has reported that though it is likely increases in life expectancy at older ages will continue, life expectancy at birth ‘is unlikely to reach levels above 95 unless there is a fundamental change in our ability to delay the ageing process’.
In her 2015 study ‘Lifespan and health span: past, present and promise’ published in the journal Gerontologist, Dr Crimmins noted: ‘We have yet to experience much compression in morbidity as the age of onset of most health problems has not increased markedly…
‘Compressing morbidity or increasing the relative healthspan will require ‘delaying ageing’ or delaying the physiological change that results in disease and disability.’
Professors Olshansky and Carnes summed up: ‘Although there is still plenty of room for improvement to reach the 85 (life expectancy at birth) limit, remember that entropy in the life table implies that an increase from 83 to 84, or 84 to 85, requires an extraordinary effort that is much more difficult to achieve than movin life expectancy from 80 to 81 – going beyond that limit still requires modifications to the underlying biology of ageing.’
The 21st century dilemma
Public health improvements played a critical role in the 30-years rise in life expectancy since 1900, with easy gains in longevity by saving the young – but these easy gains cannot happen again. Medical technology then took over in the latter part of the 20th century to ‘manufacture survival time’ for people who would otherwise have succumbed at younger ages.
In the modern era of long-lived populations, we now live long enough for ageing-related diseases to impact human health; in other words, the longer we live, the more powerful the biological process of ageing becomes a risk factor for the diseases that kill us.
These observations present humanity with a rather interesting dilemma today, noted Professor Jay Olshansky in a 2018 study titled ‘From Lifespan to Healthspan’ published in the journal JAMA.
If we continue to attack chronic fatal and disabling diseases in the future as we have in the past, ‘we might very well succeed in postponing death, but the price of this success will likely be a rise in the prevalence and severity of ageing-related conditions’.
The trade-offs ‘may no longer be favourable, as increasingly larger segments of the population survive deeper into the ‘red zone’ – a period in the lifespan when frailty and disability rise exponentially’.
The longevity dividend
Combating diseases of ageing as if they are independent of each other is ‘likely to lead to a rising prevalence and severity of ageing- related diseases’.
The solution is to ‘challenge the conventional approach to disease’, argued researchers at New York’s Mount Sinai Medical Centre in a study titled ‘New model of health promotion and disease prevention for the 21st century’ published in the journal BMJ.
Doctors Robert Butler, Richard Miller and Daniel Perry advocated that instead of attacking one disease at a time, scientists should ‘enhance the effort to combat the processes of ageing that give rise to these diseases’.
This new form of ‘primary prevention’ in an ageing world has become referred to as the ‘Longevity Dividend’ or ‘Geroscience’ – and evidence amassed in recent years indicates that ageing science shows great promise as a method of extending healthspan. In 2019, US Stanford University researchers Salah Mahmoudi, Lucy Xu and Anne Brunet published a study ‘Turning back time with emerging rejuvenation strategies’ in the journal National Cell Biology.
They noted that although ageing – associated with the ‘functional decline of all tissues and a striking increase in many diseases’ – has long been considered a one-way street, strategies to delay and potentially even reverse the ageing process have recently been developed.
Their study reviewed four emerging rejuvenation strategies – systemic factors, metabolic manipulations, senescent cell ablation and cellular reprogramming – and analysed their mechanisms of action, cellular targets, potential trade-offs and application to human ageing.
In a similar vein, researcher Saorise Kerrigan in a 2018 report for interestingengineering.com titled ‘Innovations that could reverse ageing a reality’ posed the key question: Could science really turn back the clock on ageing?; and answered: We might be closer to reverse ageing than you think.
She noted ‘though it might sound outlandish, there have been some incredible breakthroughs in the field of anti-ageing technology’ and listed 12 of the startling innovations that could make reverse ageing a reality:
- stem cell technology: reprogramming ageing cells
- targeting mutant mtDNA: repairing ageing cells
- activating splicing factors: crafting reversalogues to encourage cell division
- rejuvenate bio: reversing the process of ageing in dogs
- senolytic drugs: combining pre- existing medications to achieve reverse ageing
- synthetic peptides: intervening in the ageing process
- smoothing cells: using viruses to smoothen cell wrinkles
- young blood: pumping youth back into veins
- anti-ageing pills: treating age with medication
- reverse ageing with cannabis: improving brain function with THC
- anti-ageing bacteria: using bacteria to create anti-ageing pills
- gene deletion: deleting selective genes to increase lifespan.
Professors Olshansky and Carnes completed their ‘Inconvenient Truth’ study (noted above) with the conclusion: ‘No one can know exactly how anticipated advances in ageing biology will influence the futu e course of life expectancy, which is why we have fundamental disagreements with scientists that claim radical lifespan extension is forthcoming in the absence of empirical evidence to support this view, and in the presence of global trends indicating that limits to longevity are being approached.’ AMP
1. HUMAN LIFESPAN COULD REACH 130 BY 2100
A major 2021 study by researchers at the University of Washington has concluded there is a ‘greater than 99% probability the current maximum reported age of death (MRAD) of 122 years will be broken by 2021’ – and estimates the probabilities that a person lives to at least age 126, 128 or 130 this century as 89%, 44% and 13%.
The data also recorded a 99% probability of a person living up to 124 years this century and a 68% probability of reaching 127 years, but just 0.4% probability of someone reaching 135 by 2100.
In their study of 1,119 individuals from 10 European countries and Canada, Japan and the USA who had reached at least 110 years
of age – published on 30 June 2021 in the journal Demographic Research and titled ‘Probabilistic forecasting of maximum human lifespan by 2100 using Bayesian population projections’ – the scientists considered the problem of quantifying the human lifespan using a statistical approach that probabilistically forecasts the MRAD through 2100.
Their objective was to quantify the probability that any person ‘attains various extreme ages, such as those above 120, by the year 2100’.
They used the exponential survival model for supercentenarians (people over age 110) of Rootzen and Ahould in a 2017 Swedish study (see box 2) but extended
the forecasting shadow, quantified population uncertainty using Bayesian population projections and incorporated the most recent data from over 1,100 supercentenarians in the International Database of Longevity (IDL) – a resource that only includes people whose age can be confirmed with a high deg ee pf certainty – to ‘obtain unconditional estimates of the distribution of MRAD this century in a fully Bayesian analysis’.
The team found the exponential survival model for supercentenarians is consistent with the most recent IDL data and projections of the population aged 110-114 through 2080 are ‘sensible’.
They then integrated ‘over the posterior distributions of the exponential model parameter and uncertainty in the supercentenarian population projections to estimate an unconditional distribution of MRAD by 2100.
They summed up that, based on Bayesian analysis (a statistical model that answers research questions about unknown parameters using probability statements) ‘we have updated the supercentenarian survival model of Rootzen and Zholud using the most recent IDL data, incorporated Bayesian population projections and extended the forecasting window to create the first fully Bayesian and unconditional probabilistic projection of MRAD by 2100’.
2. UNLIKELY TO LIVE PAST 128 BEFORE 2042
In a landmark 2017 study, scientists Holger Rootzen and Dmitrii Ahould from Sweden’s Chalmers University of Technology posed the question: Does the human lifespan have an impenetrable biological upper limit which will stop further increase in life limits?
Their research paper, titled ‘Human life is unlimited – but short’ and reported on researchgate.net, studied what can be inferred from data about human mortality at extreme age.
They found that, in Western countries and Japan, after age 110 ‘the probability of dying is about 47% per year. Hence there is no finite upper limit to the human lifespan.’
However, they noted that ‘given the present state of biotechnology, it is unlikely that during the next 25 years anyone will live longer than 128 years in these countries’.
They also report that ‘data, remarkably, shows no difference in mortality after age 110 between sexes, between ages or between different lifestyles or genetic backgrounds’.
3. CAUTION RE ‘OVERLY OPTIMISTIC FORECASTS’
Amid the many revolutionary advances in medical science accompanying the initial decades of the 21st century, demographers around the globe increasingly speculate on how far human lifespan may extend for coming generations.
However, an international study titled ‘Prospects for Human Longevity’ published in the journal Science – by Professor Jay Olshansky from Chicago’s University of Illinois, Professor Bruce Carnes from the University of Oklahoma and Dr Aline Desesquelles from France’s Institut National d’Etudes Demographiques – reported that from 1985-1995, death rates for the population aged 0-99 declined at an average annual rate of 1.5% in France, 1.2% in Japan and 0.4% in the USA.
The scientists concluded: ‘The trends in mortality, if they continue, would yield a life expectancy at birth from 85-90 years in the 21st century.
‘Given the presence of entropy (the degree of disorder or randomness) in the life table, a life expectancy at birth of 100 years, if it ever occurs, is unlikely to arise until well past the time when everyone alive (at the start of the 21st century) has already died.’
They warned: ‘Overly optimistic forecasts of life expectancy have already influenced important areas of public policy.’
4. ‘HEALTH EXTENSION’ SHOULD SUPPLANT ‘LIFE EXTENSION’
At the start of 2020, Professor Jay Olshansky from the University of Illinois and Professor Bruce Carnes from the University of Oklahoma updated their warnings (see box 3) with a study titled ‘Inconvenient Truths About Human Longevity’.
They noted that while advances in public health beginning in the 19th century initiated the rise in life expectancy, recent gains ‘have been achieved by reducing death rates at middle and older ages’.
In ‘Inconvenient Truths’, the scientists presented evidence why there are limits to human longevity and predictions of ‘radical life extension are unlikely to be forthcoming’.
They argued that scientific focus on health extension should supplant life extension as the primary goal of medicine and public health.
And they emphasised that ‘promoting advances in ageing biology may allow humanity to break through biological barriers that influence both lifespan and healthspan, allowing for a welcome extension of the period of healthy life, a compression of morbidity, but only a marginal further increase in life expectancy’.
The authors emphasised obstacles to breakthroughs in ageing biology are both prevalent and challenging, but one obstacle is avoidable – ‘assertions of radical increases in life expectancy and maximum lifespan that are supported primarily by hyperbole, exaggeration, misinformation and secondary gain’.
Importantly, they argued that recent efforts to promote ageing biology based on exaggerated claims about the future of human longevity stand in the way of funding for ageing science.
Their first ‘inconvenient truth’ is that purely mathematical arguments used to support radical life extension are inherently flawed because they ‘fail to take into account the biological reality that drives longevity determination in humans’. A second ‘inconvenient truth’ is the fact that during the 20th century life expectancy at birth rose by an unprecedented 30 years – faster than at any time in recorded history. The primary reason was because infant and child mortality dropped precipitously in the first half of the century, due to advances in public health that included rising living standards and improved socioeconomic status.
When early-age mortality declines, decades of life for each person saved ‘are added back into the life table because saving a child from death enables most of them to live into their 60s, 70s and beyond’.
This ‘powerful force that brought forth the first longevity evolution and a rapid 30-year increase in life expectancy at birth, cannot happen again’.
The implication is that future large gains in life expectancy, should they occur, must result from declining middle and old age mortality. Therein lies both the dilemma and the barrier to such forecasts: the gains in longevity ‘must now come from a different
part of the age structure, and for totally different reasons’.
The authors emphasised: ‘For extrapolation-based forecasts of cohort life expectancy to come true now, cohort life expectancy for babies born today would need to be greater that 20 years higher than period life expectancy at birth – more than double the magnitude of the difference observed during the last century.
‘This view requires that medical technology in the future must manufacture far more survival time for the old than public health did a century ago for the young – we’ll leave it to the reader to decide on the plausibility of this assumption.’
A third ‘inconvenient truth’ is that forecasts of linear increases in cohort life expectancy at birth and accelerating declines in death rates at older ages ‘are not just sharp deviations from the past – they are radically different and presented directly in the face of contradicting empirical evidence that life expectancy at birth is decelerating in many developed nations’.
For example, observed mortality trends in the US between 1990 and 2017 ‘indicate definitively that the rate of improvement in life expectancy has decelerated dramatically’.
5. BIOLOGICAL DETERMINANTS OF AGEING
Stanford University Professor Leonard Hayflick has explained the four phenomena that characterise the finitude of life a e ageing, the determinants of longevity, age- associated diseases, and death.
In a study published in the journal Science, Professor Hayflick noted there are only two fundamental ways in which age changes can occur”: either as the result of ‘a purposeful program driven by genes or by events that are not guided by a program but are stochastic or random, accidental events’.
He emphasised: ‘The weight of evidence indicates genes do not drive the ageing process, but the general loss of molecular fidelity does. Potential longevity is determined by the energetics of all molecules present at and after the time of reproductive maturation.’
Professor Hayflick explained: ‘Thus every molecule, including those that compose the machinery involved in turnover, replacement and repair, becomes the substrate that experiences the thermodynamic instability characteristic of the ageing process.
‘However, the determinants of the fidelity of all molecules p oduced before and after reproductive maturity are the determinants of longevity. This process is governed by the genome.
‘Ageing does not happen in a vacuum. Ageing must be the result of changes that occur in molecules that have existed at one time with no age changes. It is the state of these pre-existing molecules that governs longevity determination.’
Professor Hayflick s study explained the distinction between the ageing process and age- associated disease is not only based on the molecular definition of ageing described above but is also rooted in several practical observations.
He noted that, unlike any disease, age changes:
- occur in every multi-cellular animal that reaches a fixed size at reproductive maturity;
- cross virtually all species barriers;
- occur in all members of a species only after the age of reproductive maturation;
- occur in all animals removed from the wild and protected by humans, even when that species probably has not experienced ageing for thousands or even millions of years;
- occur in virtually all animate and inanimate matter;
- have the same universal molecular etiology, that is thermodynamic instability.
Professor Hayflick said unlike ageing, there is ‘no disease or pathology that shares these six qualities’ – and because this critical distinction ‘is poorly understood, there is a continuing belief that the resolution of age-associated diseases will advance our understanding of the fundamental ageing process. It will not.’
Professor Hayflick s study argued the distinction between disease and ageing is also critical for establishing science policy because ‘although policy makers understand the funding of research on age-associated diseases is an unquestioned good, they also must understand that the resolution of age-associated diseases will not provide insights into understanding the fundamental biology of age changes.
‘They often believe that it will, and base decisions on that misunderstanding. The impact has been to fund research on age- associated diseases at several orders of magnitude greater than what is available for research on the biology of ageing.’
Professor Hayflick concluded there is ‘almost universal belief by geriatricians and others that the greatest risk factor for all the leading causes of death is old age.
‘Why then are we not devoting significantly g eater resources to understanding more about the greatest risk factor for every age- associated pathology by attempting to answer this fundamental question: What changes occur in biomolecules that lead to the manifestations of ageing at higher orders of complexity and then increase vulnerability to all age- associated pathology?’
6. THE ‘LAW OF MORTALITY’
A scientific ‘Law Of Mortality’ first proposed by British mathematician Benjamin Gompertz in 1825 – based on the assumption a person’s resistance to death decreases as his/her years increase – has been comprehensively studied and debated over the ensuing two centuries.
Among a series of landmark scientific studies assessing its merits across almost 200 years, it has been variously:
- confirmed by English actuary and mathematician William Makeham in his 1867 paper ‘On the Law of Mortality’;
- studied by US biologist Jacques Loeb and biochemist John Northrop in their 1916 paper ‘Is there a temperature coefficient for the duration of life?’ and by Scottish medical statistician John Brownlee in his 1919 paper ‘Notes on the biology of a life table’;
- empirically evaluated by British biologist Mark Greenwood in his 1928 paper ‘Laws of mortality from the biological point of view’ and US biologist Raymond Pearl in both his 1921 paper ‘Empirical studies on the duration of life’ and his 1922 paper ‘A comparison of the laws of mortality in Drosophilia and in man’;
- re-evaluated by US biologist Edward Deevey in his 1947 paper ‘Life tables for natura populations of animals’;
- and the dynamics of human mortality behind the ‘Law of Mortality’ were finally explained by US academics Bruce Carnes, Jay Olshansky and Dennis Grahn in their 1996 paper ‘Continuing the search for a low of mortality’.
Subsequently Professors Olshansky and Cranes concluded in a 2013 study titled ‘A measured breath of life’ that ‘the life expectancy limit for humans was approximately 85 years at birth’.
