Lifespan is the term used to describe the maximum length of time that a living organism can survive. The lifespan of humans has increased significantly over the past centuries, thanks to advances in medicine, nutrition, sanitation and other factors. But how long can humans live, and what are the limits of human longevity?

According to the World Health Organization (WHO), the average life expectancy at birth for the global population in 2019 was 72.6 years. However, this figure varies widely depending on the region, country, gender and other factors. For example, the life expectancy at birth for Japan was 84.3 years, while for Sierra Leone it was 54.3 years. Similarly, women tend to live longer than men, with a global average of 74.9 years versus 70.4 years.

But life expectancy is not the same as lifespan. Life expectancy is the average number of years that a person can expect to live based on current mortality rates and trends. Lifespan is the maximum number of years that a person can potentially live, regardless of external factors. The longest verified lifespan for a human is 122 years and 164 days, achieved by Jeanne Calment of France, who died in 1997.

Scientists have different theories and hypotheses about what determines the lifespan of humans and other organisms. Some believe that there is a genetic component that sets a limit on how long cells can divide and function properly. Others suggest that aging is caused by the accumulation of damage and errors in the DNA, proteins and other molecules that make up the cells. Still others argue that aging is influenced by environmental factors such as stress, diet, exercise and exposure to toxins.

Regardless of the exact mechanisms, most researchers agree that there is no fixed limit to human lifespan, and that it is possible to extend it through various interventions. Some of these interventions include caloric restriction, gene therapy, stem cell therapy, anti-aging drugs and nanotechnology. However, these interventions are still experimental and have not been proven to be safe or effective in humans.

Therefore, the question of how long humans can live remains unanswered and open to speculation. Some experts estimate that the maximum human lifespan could range from 120 to 150 years, while others claim that it could be much higher or even unlimited. Ultimately, the answer may depend on how we define life and death, and whether we are willing to accept the trade-offs and ethical implications of extending our lifespan beyond its natural boundaries.

One of the main challenges of studying human lifespan is the lack of reliable data and methods. Most historical records of human longevity are incomplete, inaccurate or fraudulent. Even today, there are many cases of people who claim to be much older than they really are, or who have no official documentation to verify their age. Therefore, it is difficult to determine the true distribution and trends of human lifespan across different populations and time periods.

Another challenge is the ethical and social implications of extending human lifespan. While many people may desire to live longer and healthier lives, there are also potential drawbacks and risks associated with increasing longevity. For instance, longer lifespan could lead to overpopulation, resource depletion, environmental degradation and social inequality. Moreover, longer lifespan could affect the quality and meaning of life, as well as the values and norms of society. For example, how would longer lifespan affect family structures, career paths, education systems and cultural traditions?

Therefore, the quest for human lifespan extension is not only a scientific and technological challenge, but also a philosophical and moral one. It requires us to reflect on what it means to be human, and what kind of future we want for ourselves and our descendants. It also requires us to balance our individual aspirations with our collective responsibilities and obligations. Ultimately, the question of how long humans can live may not have a definitive answer, but rather a range of possible scenarios that depend on our choices and actions.