- My Longevity Experiment
- Posts
- Is our Extended Longevity just the result of us Not Dying Younger?
Is our Extended Longevity just the result of us Not Dying Younger?
This is why the longer you live, the steeper the climb toward mortality.
My Longevity Experiment
September 09, 2024
Is our Extended Longevity just the result of us Not Dying Younger?
This is why the longer you live, the steeper the climb toward mortality.
Are We Living Longer?
Since the mid-1800s, human life expectancy has steadily increased by approximately three months each year. This remarkable progress is largely attributed to a shift in mortality, where deaths that once occurred earlier in life are now delayed to later stages. However, despite this shift, there is no indication that the rate at which mortality increases with age is slowing.
The rise in life expectancy, particularly in developed nations, has been driven by advancements in public health and lifestyle. As a result, more individuals are living long enough to experience age-related decline in function and an increased prevalence of age-related diseases. This growing population of older individuals underscores the need to focus on not just extending life but improving the health and quality of life in later years.
Looking ahead, significant extensions of human longevity will likely depend on whether science can slow the biological process of aging or find ways to reduce mortality in the later stages of life.
Cross-Species Correlation in Aging
Research has long established a strong correlation between rates of aging and other life history traits across species. Factors such as pre-adult mortality, age at first reproduction, birth rate, metabolic rate, and generation length, as well as morphological traits like adult body size and growth rate, are all linked to the aging process. These correlations suggest that aging evolves in tandem with these traits, potentially placing constraints on how much the aging process can be altered within any given species.
It has been widely hypothesized that the rate of aging is relatively fixed within species, not only in humans but also in animals. This suggests that while external factors such as environment and health interventions can influence life expectancy, the fundamental biology of aging may remain constant.
The Study
A recent study set out to test the "invariant rate of aging" hypothesis, which posits that a species’ rate of aging is fixed from adulthood. This ambitious research was conducted by an international team of scientists from 14 countries, including José Manuel Aburto from Oxford's Leverhulme Centre for Demographic Science. The team analyzed centuries of age-specific birth and death data spanning multiple continents.
The study, led by Fernando Colchero of the University of Southern Denmark and Susan Alberts of Duke University, required decades of monitoring wild populations of primates, in addition to gathering human demographic data.
Key Insights
Dr. José Manuel Aburto from Oxford University’s Leverhulme Centre for Demographic Science highlighted the study's findings, stating: “Our findings support the theory that, rather than slowing down death, more people are living much longer due to a reduction in mortality at younger ages. We compared birth and death data from humans and non-human primates and found this general pattern of mortality was the same in all of them. This suggests that biological, rather than environmental factors, ultimately control longevity.”
This research provides important insights into the long-standing debate about human lifespan. For decades, the academic community has been divided over whether human lifespan has a biological limit. Some scholars argue that humans can theoretically live much longer, while others believe that our lifespan is capped.
However, what has been missing from this debate is a comprehensive comparison of the lifespans of various animal populations alongside humans. This study fills that gap by examining mortality trends across a wide array of species.
The Results
The researchers examined birth and death records from nine diverse human populations, ranging from 17th to 20th century Europe, the Caribbean, Ukraine, and two hunter-gatherer groups between 1900 and 2000. In addition, they analyzed data from 30 primate species, both in the wild and in captivity, including gorillas, baboons, and chimpanzees.
The results were strikingly consistent across both human and non-human species. All datasets revealed a similar mortality pattern: a high risk of death in infancy that rapidly declines in childhood and teenage years, remains low in early adulthood, and then steadily rises with advancing age.
Dr. José Manuel Aburto elaborated on the findings: “The statistics confirmed that individuals live longer as health and living conditions improve, which leads to increasing longevity across an entire population. Nevertheless, a steep rise in death rates, as years advance into old age, is clear to see in all species.”
Conclusion
The study concludes that while improvements in health and living conditions have extended life expectancy, the trajectory toward death in old age has not changed. Dr. Aburto summarized: “Our findings confirm that, in historical populations, life expectancy was low because many people died young. But as medical, social, and environmental improvements continued, life expectancy increased. More and more people get to live much longer now. However, the trajectory toward death in old age has not changed. This study suggests evolutionary biology trumps everything, and so far, medical advances have been unable to beat these biological constraints."
Implications for the Future
The team’s findings could have far-reaching implications, not only for understanding human longevity but also for the study of ecology and the evolution of aging across a wide range of species. This research may also contribute to conservation efforts, providing valuable insights into the life history traits that influence aging and survival in endangered species.
Study Links: