The natural life span of human beings is similar to that of mammals, and there are several calculation methods. It is generally believed that the maximum life span of living things is about 8 ~ 10 times of sexual maturity, while the sexual maturity of human beings is 14 ~ 15 years. According to this calculation, the maximum natural life span of human beings should be 1 12 ~ 150 years. In other words, the life span of mammals is 5 ~ 7 times of its growth period, and the growth and development period of human beings is 20 ~ 25 years old, so the natural life span of human beings is 100 ~ 175 years old; There is also a saying that according to the number of cell passages, research experiments have proved that human cells divide and pass in vitro for about 50 times. According to the average division cycle of 2.4 years, the average life expectancy of people should be 120 years. According to the above calculation, there is no doubt that the natural life span of human beings exceeds 100 years. The life span of people in different countries is closely related to their economic level, cultural quality, customs, medical and health conditions, geographical environment, climate and many other factors. In a sense, the average life span of human beings is an important symbol of modern civilization. 4,000 years ago, in the bronze age when productivity was low, the average life expectancy of people was only 18 years old, while in ancient Rome it was 23-25 years old. In the future, with the development of production and the progress of science and technology, the average life expectancy will be higher and higher. Take Japan as an example:1In the middle of the 8th century, the average life expectancy of people was 35 years; 1953, with an average life expectancy of 50.6 years for men and 53.9 years for women; 1965, male 67.74 years old, female 72.92 years old; From 65438 to 0995, the average life expectancy of men was 76.57 years and that of women was 82.98 years. However, the average life expectancy in the poorest countries in Africa is only about 40 years old. For example, in Uganda, a central African country, 1993 has an average life expectancy of only 43 years. This shows that economic level is closely related to life expectancy. According to the announcement of 1973 World Health Organization, the average life expectancy of men is over 70 years, and that of women is over 75 years. Sweden, Japan, Netherlands, Norway, Iceland and other seven countries. 1996, the world health organization announced that 1995, the average life expectancy in the world exceeded 65 years, which was about 3 years higher than 1985. The average life expectancy in developing countries is over 75 years, 64 years in developing countries and 62 years in underdeveloped countries. The country with the longest life expectancy is Japan at 79.7 years, followed by Greece at 79.2 years. The country with the shortest life expectancy is Sierra Leone, only 40 years old. At present, the life expectancy of women is 67.2 years and that of men is 63 years. In Europe, the life expectancy of women is 8 years higher than that of men, while in Southeast Asia, the life expectancy of women is only 1 year higher than that of men. In China, the average life expectancy of ancestors in primitive society is only 22 years old. From the Xia Dynasty in 2 1 century BC to the Revolution of 1911 in19/1year, after more than 4,000 years, there were about 67 dynasties and 446 emperors (excluding the warring states), and their average life expectancy was only 42 years. Before liberation, the average life expectancy of our population was only 35 years old. After liberation, with the improvement of people's material living standards and medical and health conditions, the average life expectancy of the population has increased by nearly 1 times, from 1.985 years to 68.92 years, and is now close to 70 years old. If the national population over 60 is calculated, 10. 1% at the end of 1999,1%in 2000 and 20% in 2025, it is expected to reach the peak of growth in 2050, and the total number will exceed 400 million. By then, one in four people will be an elderly person. Due to the extension of human life span, the division of the elderly has also changed from the past. In the past, it was divided into 4 ~ 14 years old as childhood, 15 ~ 34 years old as youth, 35 ~ 44 years old as middle age, 45 ~ 59 years old as pre-senile, 60 ~ 89 years old as old age, and over 90 years old as long-lived old age. According to the classification of the World Health Organization, young people are under 44 years old, middle-aged people are 45-60 years old, young people are 60-75 years old, old people are 75-90 years old, and those who live long are over 90 years old. Beautiful natural environment is not only beneficial to health, but also can beautify people's lives and hearts. It provides a comfortable, quiet and beautiful living environment for families and individuals, and is the cradle of health, happiness and longevity. For example, the five famous longevity areas in the world-Caucasus in the former Soviet Union, Hanseatic in Pakistan, Cali in Ecuador, Nanjiang in Xinjiang, China and Bama in Guangxi. It is an area with beautiful environment, suitable temperature, green mountains and green waters, fresh air and clean water sources. From the perspective of urban and rural distribution, there are more elderly people in rural areas than in cities, and mountainous areas are higher than plain areas. This is all related to the natural environment. Generally speaking, there is no pollution in rural areas and the air is fresh, while industrial wastewater, waste gas and waste residue in cities, especially industrial and mining areas, pollute the environment, worsen the natural environment and lead to diseases. People's life span is not only related to the external environment, but also closely related to the internal environment. The internal environment affects life span through injury, load and disease. For example, the oxygen load in cells has a direct impact on cell aging, and oxygen molecules are dual, which are necessary for survival and have potential toxicity, which has a negative impact on the long-term survival of cells. Oxygen free radicals can cause DNA damage, which is an important factor affecting the aging process. About 1% ~ 4% of oxygen molecules in mitochondria can be converted into oxygen free radicals, causing extensive oxidative damage to biological macromolecules, leading to inactivation and degradation of protein molecules, base exchange and single strand breaks in DNA. At the same time, protein, DNA and other biological macromolecules can be slowly glycosylated with glucose in a non-ester manner, and these glycosyl groups are gradually oxidized, so that protein and ester nucleic acids (such as DNA) are widely crosslinked to form lipofuscin (senile plaque). The exchange of collagen and elastin can lead to stiffness of connective tissue and myocardium, reduction of water content, atrophy of limbs, and loss of elasticity of tendons and blood vessels, thus leading to aging. The influence of heredity on longevity is more prominent in people who live longer. Generally speaking, parents live longer and their children live longer. According to the survey report of a German scientist, he surveyed 576 centenarians in 15 years and found that the average age of their parents' death was 9 ~ 10 years older than the average person. According to the survey of centenarians in Guangdong Province, 84.6% of them live a long life in their families. Statistics show that the older the population, the higher the family longevity rate. For example, among the elderly aged 80-84, the longevity rate of their families is 52%. In the population aged 105, the family longevity rate is 7 1%. 1992, the world health organization announced that 15% of many factors that affect everyone's health and longevity depends on genetic factors. Theoretically speaking, heredity is a biological characteristic. Without heredity, there would be no biological reproduction. Biological characteristics are determined by genetic characteristics. The so-called "As you sow, you reap what you sow" and "Dragon begets Dragon, Phoenix begets Phoenix" are common phenomena of genetic characteristics. Heredity has specificity, and the specificity of heredity determines various biological species. The differences of biological species (including interspecies and intraspecies) are determined by genetic specificity. For human beings, everyone (male and female) is not only different in appearance, but also different in personality. This is a genetically specific phenomenon. In nature, there are not only population-specific phenomena, but also population-specific longevity phenomena. The life span of each population is almost fixed, that is, the life span is fixed by genetic material, the so-called gene. The difference of genetic genes in each population determines the difference of life span of each population. This strongly explains why some people live long and others live short. One of the reasons is the result of parental genetic inheritance. This fact strongly proves that the difference between one individual and another in a specific population (including the difference in life span) is undoubtedly caused by genetic variation among individuals and the aging process of environmental factors. Diet, nutritional factors, diet and nutrition are closely related to longevity. The diet structure of centenarians in Changshou area of Chinese mainland is mainly low in calories, fat, animal protein and vegetables. Although milk, dairy products, sheep and beef protein are the main dietary sources of the elderly in Xinjiang, they often eat coarse grains and have no other bad hobbies. There are 1000 centenarians in Sichuan, most of whom are vegetarians and often eat vegetables and bean products. There was a longevity village in the former Soviet Union. The average age of villagers is 120 years old. The longevity of villagers is related to drinking mulberry juice. Centenarians in Bama Yao Autonomous County of Guangxi like to drink a kind of rice wine. The longevity of Greeks is an important factor, and the food structure is mainly starch, fish, olive oil and fruit. From the perspective of personal health and longevity, for example, one of the secrets of Bingxin's health care is that his diet is extremely ordinary, he eats three meals a day and likes to eat coarse grains and vegetables. The eating habits of the Queen of England are surprisingly simple. It is said that a celery and a few lettuce leaves are lunch. With the progress of society, people's life expectancy has been continuously extended. For example, the average life expectancy in Boston and new york is very close. From 18 10 to 1820, the average life expectancy was 27.85 years and 26. 15 years respectively, and from 1840 to 1845, it was 265438 years. This increase in life expectancy is not only due to the improvement of medical conditions and the effective prevention and treatment of some diseases, but also due to various contributions made by nutrition science and technology, which is closely related to food nutrition, food safety and quality, and dietary balance. In recent years, with the development of economy, great changes have taken place in the diet structure of China residents. Compared with the 1980s, meat consumption increased by more than 80% in the early 1990s. In areas with high consumption of meat, eggs and fat, the mortality of cancer, cardiovascular and cerebrovascular diseases and diabetes is obviously higher, which shows the influence of changes in diet structure on life expectancy. In recent years, some people think that dieting can reduce oxygen load, that is, reduce the production of oxygen free radicals, reduce the level of glucose and reduce the production of non-enzymatic glycosylation; Improve apoptosis, eliminate precancerous cells and reduce cancer incidence. In addition to moderate food restriction, we should also develop healthy eating habits and eat more foods that eliminate free radicals, that is, foods with high vitamin E and C content, such as eggplant, leeks and carrots. Psychological (or spiritual) factors People's psychology and emotions are closely related to health and longevity. People who are often in a state of psychological tension are often prone to illness. On the contrary, optimism and perseverance can enhance the body's disease resistance. Because excessive tension will make the heart beat faster, blood pressure rise, shortness of breath, insufficient blood supply to gastrointestinal organs and so on. Over time, it is easy to cause cerebral vascular rupture or fatal myocardial infarction, and some will also have gastrointestinal spasm and pain. If you are too sad, you will also get sick, leading to short life. Lifestyle factors Diseases caused by unhealthy lifestyles are the biggest cause of death for human beings in the world. In developed countries, 70% ~ 80% people die of heart disease, stroke, hypertension and tumor. These so-called "lifestyle diseases" account for more than 50% of its mortality. The unhealthy lifestyle is mainly eating too much oil, too salty and too sweet, and drinking hard liquor, smoking a lot, coveting enjoyment, staying overnight for a long time and doing less exercise, and even gambling, indulgence and drug abuse. Disease factors Disease is the most important factor affecting life expectancy. As the cause of death, disease is constantly changing with the progress of the times and the development of science and technology. For example, at the beginning of the 20th century, the main life-threatening diseases were infectious diseases, pneumonia and tuberculosis. At present, the biggest threats to human life are cardiovascular and cerebrovascular diseases, tumors and accidental injuries. Moreover, some diseases, such as immunodeficiency, Alzheimer's disease, AIDS and so on. It does pose a great threat to human health and life. Family factors A person spends most of his life in his family. The quality of family environment, especially the relationship between husband and wife, is directly related to the psychological and physical health of human body, and then affects life expectancy. Medically speaking, quarreling and sulking between husband and wife will lead to an increase in hormones in the body, which will lead to diseases. Moreover, nervous family members and bad mental state can easily lead to many physical and mental diseases and damage life expectancy. Therefore, it is very important for people's physical and mental health and family happiness to maintain harmonious, friendly and pleasant family relations and treat everything with optimism, cheerfulness, always smiling and generosity. There is a clear relationship between gender and life expectancy. It is universally acknowledged that women live longer than men. This is mainly determined by the biological characteristics of different sexes, and may also be related to the lower metabolic rate of women than men and the endocrine differences between men and women. In recent years, a study shows that the change of the length of the terminal region of human somatic cells (terminal region refers to the special structure of the chromosome end of genetic material) is one of the specific biological age markers of human beings. From the study of the length of peripheral white blood cells in human body, it is found that in the same age group, the length of male peripheral white blood cells is lost faster than that of female. According to the terminal zone hypothesis, the terminal zone length decreases with age, that is, the shorter the terminal zone length, the higher the age, the faster the terminal zone length loss and the faster the aging; On the contrary, the longer the end band length, the younger the age, the slower the end band length loss and the slower the aging. Men lose their telomere length faster than women, so they age faster, that is, they live shorter lives than women. This theory can explain why women tend to live longer than men, which is a human social phenomenon. Occupational factors Life expectancy is also related to occupation. People engaged in dangerous occupations have high mortality and short life expectancy, such as high mortality of aircraft pilots; Workers engaged in radiation research have a short life span.