The oldest person ever recorded to have lived on Earth reached an impressive 122 years and 164 days. That is, of course, assuming she truly was who she claimed to be, as some doubts were raised on this matter as early as 2019. But what is the actual maximum age humans might realistically achieve?
A fresh piece of research explores this question by examining our individual organs and estimating how long they might continue to operate if we could eliminate all other reversible aging processes. The findings have been published in the journal NPJ Aging.
The research team concentrated on determining how long each of our organs could survive if somatic mutations—those that occur after conception and may involve issues like DNA copying errors during normal cell division—were the only factor at play.
“Up until now, no attempts have been made to estimate how long a person might live in the future after undergoing treatments that prevent reversible aging,” the researchers explain. “What would be the maximum benefit from radical life extension, setting aside extravagant interventions like wholesale cell replacement or uploading consciousness onto a silicon chip? In other words, what is all this effort for?”
This required extensive mathematical calculations and a number of assumptions. The first was the assumption that the mortality rate for all people matches that of a 30-year-old Swiss individual. This might seem surprising, but it is quite reasonable given the complexity of the task.
The team wanted to examine human life expectancy when certain factors are excluded. To do this, they needed a baseline expected mortality rate for an average person.
If aging is not taken into account, people would still die from accidents, viruses, or, for instance, falling into a hot spring in Yellowstone.
The team needed to build their model based on a population where age-related diseases played as small a role as possible in mortality rates. They chose Switzerland due to its low mortality rates, as well as individuals aged 30, because they tend to be healthy yet still face a notable risk of death from causes such as illness, workplace accidents, and substance abuse.
In this idealized world, where the risk of death does not increase with age, people could, according to the research team, live extremely long lives.
“As a baseline, we take the mortality rate at age 30, which corresponds to a median and maximum remaining life expectancy of 1,759 and 29,221 years, respectively,” they write in their paper.
That is a vast number of years, and it to some extent illustrates just how much aging amplifies mortality risk, until eventually survival drops to zero for everyone. If, for example, a modern-day 110-year-old were used as a baseline, the average remaining life expectancy for all would shrink to just one year.
In their model, the team then turned various aging processes on and off and studied the expected lifespans of our organs.
By mathematically modeling all these juicy, squishy parts inside us and factoring in only somatic mutations, the team discovered that our maximum possible lifespan is constrained by several key organs. While having a brain is beneficial (for the most part), its components may prevent us from living much longer than we currently do.
“A key finding of the study is the discovery of substantial differences between tissue types,” explained co-author Evgeny Efimov from the Center for Biomedical Technologies at Skoltech and the Artificial Intelligence Research Institute (Russia).
Neurons and cardiomyocytes, which lack the ability to divide, emerged as the primary limiting factors: when all other causes of aging are removed, somatic mutations alone reduce the theoretical average lifespan from 1,759 years (for a hypothetical non-aging human body) to 156 years.
“At the same time, tissues with high regenerative capacity, such as the liver, can maintain their function for thousands of years due to continuous cell renewal, effectively neutralizing the negative impact of mutations,” added Efimov.
This is the median age, while the maximum lifespan reached 470 years. You may have noticed that we don’t have many people over 400 years old, and one interesting aspect of the study is that it could help the team understand which factors actually contribute to aging.
“Our study shows that somatic mutations make a significant contribution to aging, but they alone cannot explain the mortality we observe,” added co-author Dmitry Kriukov from the Center for Biomedical Technologies at Skoltech and the Artificial Intelligence Research Institute. “This means that other aging mechanisms, such as loss of proteostasis, mitochondrial dysfunction, or epigenetic changes, contribute comparably to limiting lifespan.”
The research team writes that, according to the results, aging in humans is uneven because it affects different organs—like the brain and heart—more quickly. This means that attempts to extend lifespan should target key areas of the body.
“In this context, translational cell therapy aimed at replacing neurons may represent our only viable path to extending lifespan beyond 150 years, even if all other hallmarks are mitigated,” they write.
Despite the progress we have certainly made in extending human lifespan, according to this work, the maximum possible average human lifespan may range from 146 to 194 years, and is limited by somatic mutations.
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