Immortality is certainly the forbidden dream of our species. And if for now it remains a mirage, science is working to develop techniques and therapies that can extend human life as much as possible. What age could we reach with similar interventions? The answer comes from a study led by computational biologist Dmitrii Kriukov, from the Skolkovo Institute of Science and Technology in Russia, and published in the journal npj Aging: his calculations indicate that the wear and tear that our DNA undergoes over time establishes an insurmountable barrier, setting the maximum life expectancy of our species in a range between 150 and 190 years.
The accumulation of mutations
Throughout life, each cell division carries the risk of small errors in the replication of the genetic code. Although our body has efficient repair systems designed specifically to resolve this type of “copying errors”, a portion of these alterations, known as somatic mutations (which occur in somatic cells, and are therefore not heritable), always manages to escape controls.
In most cases they are perfectly harmless, but sometimes they can lead to serious diseases, such as cancer. The working group led by Kriukov created a mathematical model to evaluate how the mutation rate affects the functioning of the main human organs, calculating the survival that an ideal human population, completely free from age-related pathologies, could aspire to. With the aim of quantifying the contribution of genetic wear and tear to the deterioration of our organism, isolating it from all other environmental and biological factors.
Each organ has its own story
The simulation results show that not all body structures react in the same way to the passage of time. Several tissues, including the skin and liver, maintain the ability to continually renew themselves by replacing damaged cells. In contrast, vital organs such as the brain and heart are predominantly composed of very long-lived cells that are rarely replaced throughout life.
It is precisely these cells that accumulate the greatest quantity of genetic errors, becoming the critical point that limits the overall survival of our organism. In fact, when the load of mutations in these organs reaches a critical threshold, functionality is irreversibly compromised, regardless of the general health of the rest of our body.
Longevity research
For now, Kriukov’s findings don’t help us understand how we might extend our lives beyond their current limits. However, they confirm that aging is an extremely complex phenomenon, and that only by studying this complexity, and acting on multiple factors that influence the length of our life, will we be able to reach the future. The results obtained by Kriukov place the theoretical limit of survival of our species at around 150-190 years. A goal quite far from the current human lifespan, which is around 79 years on average, and which even in the longest-lived people does not exceed much more than a century. According to the researcher, this means that other physiological processes intervene to shorten human existence long before the accumulation of harmful mutations ends it. Or to discover effective therapies to extend our lives. And this finding is, in itself, an important indication for future research in the field of human longevity.
“Our work represents a critical first step toward breaking down aging into quantifiable components,” the study authors write. “Ultimately, the integration of other key factors of aging could pave the way to a comprehensive, mechanistic theory of aging itself. Achieving this will require coordinated efforts between different research groups – a challenging prospect, but achievable in the near future.”