In life, there will be death. However, many people do not understand the criteria and process of judging death. How can death be considered? What changes will happen to your body when you are on the verge of death? How should we face death? Does humans have a way to defeat death? Next, let us think carefully about how to view death scientifically.
There are four parts in this article. The following mind map summarizes the structure directory of this article.
Part 4: Can humans defeat death?
Everyone wants to stay away from death as much as possible. Since ancient times, human beings have dreamed of being able to live forever one day. So, why can't humans live forever? What determines a person's lifespan? Through recent research, its secrets have gradually surfaced. This section will introduce the latest research on death and lifespan, and explore the extent to which humans can defeat death in the future.
1. Lifespan growth
The graph of the average lifespan embodies the history of this country
1800, the global average lifespan was about 30 years old, and in 2019 it increased to 72.6 years, more than tripled. The average life expectancy of the Japanese was greatly reduced due to World War II , and was greatly restored after the war in 1945. The average life expectancy of Koreans was also greatly reduced during the Korean War (1950-1953). Although the average life expectancy in South Africa has declined from 1990 to 2000 due to AIDS , it has a trend of recovery in recent years.
The average lifespan of humans has more than tripled in two hundred years
Time back, if the ancients two hundred years ago could travel to the modern era and know that "the average lifespan of humans is more than 70 years old" would be so surprised! Around 1800, the average life span of humans was only about 30 years, and in no country reached 40 years.
Human life span has achieved a sharp increase in the past two hundred years. According to statistics from the United Nations, the global average life expectancy was 72.6 years in 2019, which means that the average life expectancy of humans has more than tripled in two hundred years.
The life expectancy limit of humans is 125 years old?
Although the world average life expectancy has a further growth trend. But the world's highest age record has not been updated since 1997. In 2016, a research team from the Albert Einstein School of Medicine in the United States analyzed global statistics in detail and concluded that "the limit of human lifespan of is 125 years old ."
2. Telomeres
The length of telomeres in cells is closely related to lifespan
Why can't humans live forever? Biologists have discovered that the cells that make up our body are hidden in the cells that determine lifespan-telomeres.
It is said that the average length of telomeres (number of DNA base pairs) is 10,000 in infancy, 7500 at age 35, and about 4800 at age 65. Telomeres have the function of protecting the ends of chromosomes.
If the length of the telomeres reaches its limit and cannot be shortened, the cells will not be able to continue to divide. The cleavage limit caused by telomeres length is named by the proposer and is called "Haiflick limit" .
3. Cancer
The longer the life span, the greater the chance of cancer. Can humans eliminate cancer?
The proportion of children and young people who die from cancer is low, but as they age, the proportion of cancer and deaths from cancer will gradually increase. In Japan, about half of the elderly over 70 suffer from cancer, and about half of them die from it.
Cancer is caused by DNA damage, and DNA damage is caused by ultraviolet rays and harmful substances. Even without these damages, DNA replication will occur to a certain extent when cells divide . Although cells have mechanisms to repair this error, if repair fails, DNA can be damaged.
Therefore, the longer a person lives, the more damage to DNA and the greater the possibility of cancer. Although the body's own immune function can clear cancer cells, it is difficult to remove cancer cells if their immune function is reduced due to aging. For humans who have achieved longevity, cancer may be an inescapable fate.The survival rate of
cancer has been greatly improved
cancer treatment and early screening methods are constantly improving. In Japan, statistical results released in 2020 showed that the 5-year survival rate of cancer was 68.4%, a significant increase from the 53.2% survival rate in the 1990s.
If humans can eliminate cancer in the future, their lifespan should be further improved. The key is to minimize the damage of ultraviolet rays and harmful substances, improve DNA repair capabilities and immune functions, and further improve early screening and treatment methods for cancer.
At present, there are still many unsolved mysteries in terms of DNA repair mechanism and immune function, and scientists are working hard to overcome these difficulties. The study found that rodents like naked mole rat are almost free from cancer, so their mechanisms are being studied in depth.
Decreased immune function will cause cancer cells to be unable to remove
The human body's own immune system can not only quickly discover and remove "external enemies" such as pathogens, but also quickly discover and remove cancer cells produced in the body. If cancer cells escape this mechanism and continue to grow, it can lead to death.
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