Are humans capable of living beyond 200 years? How about 500 years? Using the human genome and genes from other mammals, researchers from Australia’s natural science agency, Commonwealth Scientific and Industrial Research Organization (CSIRO), tried to decipher the human longevity riddle. By developing a genetic time clock that maps the number of years a species is likely to survive, the research uncovered that our genetic programming allows us a natural lifespan of up to 38 years only. While this discovery may sound disheartening, there are reasons to remain optimistic. First of all, humans have obviously figured out how to surpass that. Second, with bold developments in science and medicine, future generations might be able to add even more years and increase human longevity.
By the turn of the 21st century, the average life span of humans has soared to 75 years. Considering the human’s genetic programming and various environmental factors that can hasten aging—our quest for human longevity has been quite successful.
Senescence: A Look at Aging on a Cellular Level
Understanding what influences an organism’s life span starts by looking into the causes of aging. Cells— the basic building block of all living things—reproduce through the process of cell division called mitosis. Growth and repair, especially in a multicellular organism, occur because of mitosis. In humans, regeneration of tissues, repair of organs, and recovery from illnesses depend on our cells’ ability to divide and replicate itself.
But here’s the catch—our cells have a limit (referred to as the Hayflick Limit). In humans, cells cannot divide beyond 50 times. Once this limit has been reached, cells become senescent and float within our system. When these senescent cells accumulate, it can cause problems within surrounding tissues. In fact, studies show that senescent cells are the leading cause of age-related diseases. It explains why medical conditions—such as arthritis, diabetes, heart diseases, and neurodegenerative diseases—start surfacing in advanced age.
While aging is a natural phenomenon, cellular aging can be accelerated due to a variety of factors. Our cells can take a beating from prolonged exposure to ultraviolet rays, pollution and stressful environments. Our lifestyle choices can contribute, too. Poor diet, alcohol and smoking have been known to play a part in faster cellular aging. With accelerated cellular aging, the risks of chronic diseases increase. Subsequently, that lengthens the years spent in pain and can negatively impact human longevity.
The Discovery of Telomerase
What dictates the lifespan of cells? What triggers cells to stop replication? The answer, in fact, is embedded within the cells. In 2009, three geneticists—Elizabeth H. Blackburn, Carol W. Greider and Jack W. Szostak—discovered the presence of telomeres, the protective cap found at the ends of chromosomes. Every time the cells divide and chromosomes are replicated, the telomeres get shorter. Once the telomeres have been completely worn out, the cell will stop replicating itself and reach its senescent stage.
Under the same research, Elizabeth Blackburn and Carol Greider were credited for the discovery of telomerase. Telomerase is the enzyme that assists in keeping the telomeres longer. By observing pond scum, they discovered the capacity of the telomerase to replenish and restore the length of telomeres. Since then, various researches have been launched to study telomerase in animals and how the enzyme can be harnessed to delay cellular aging.
Telomerase in Plants: The Quest for Human Longevity Continues
Notably, researchers from Arizona State University and Texas A&M University recently discovered the presence of telomerase in land plants. For the scientific community, that is exciting news. Most of the previous studies on telomeres and telomerase focused on animals. The telomerase enzyme found in plants offers new details about cellular aging. Certain species of cypress and pine trees can live for thousands of years. Thus, a closer look at the molecular structure of these species can shed light on plants’ telomeric limit.
Understanding the difference between animal and plant telomerase could be the breakthrough researchers are waiting for. Undoubtedly, the discovery of telomerase in plants affords us a new branch to pursue in exploring aging and human longevity.
Yes, with modern medicine and continuing extensive research, humans have covered the right amount of groundwork in understanding the science behind aging. As the field of gerontology progresses, scientists are shifting the focus from expanding lifespan to increasing people’s healthspan. With the focus moving away from human longevity per se, the objective now is to achieve better life quality and reduce the number of indisposed years. Immortality is not the goal. The ideal is to live long, fulfilling lives without the difficulties and challenges that come with aging.
