Hasn't human life reached its peak yet?

Hasn't human life reached its peak yet?

In 1825, Benjamin Gompertz, an Englishman, briefly summarized the relationship between age and mortality as exponential growth: for every eight years of age increase, the mortality rate doubled. Gompertz's law of mortality still guides our understanding of natural mortality. It's worth noting that Gompertz set his law for 30 to 80 years old. What about after 80 years old?

Biologists have long observed that many commonly used experimental insects, such as flies, wasps and bean weevils, have an interesting phenomenon in the process of aging: the mortality rate decreases with age at a certain stage, and then enters a plateau stage, no longer growing. In the past two centuries, a large number of demographic studies have found similar phenomena. After the age of 80, the growth of human mortality has begun to slow down, while some studies, including those of the very oldest people, believe that the death rate will no longer increase until the age of 110. Some mathematical models even predict that mortality may decline after 110 years of age.

However, the data quality of human aging and death census has been questioned. When collecting demographic information on a large scale, the cognitive ability of the elderly declines and their age is exaggerated, which makes false reports and false reports very common. It is almost impossible to verify the vast amount of data one by one. Therefore, although the research on mortality at the very high life stage has attracted much attention, it has not been very convincing due to the lack of strong evidence.

Recently, a high-quality demographic study has finally filled this gap. A team led by Elisabetta Barbi, a professor of demography at the University of Rome, and Francesco Lagona, a professor of demography at the Third University of Rome, used social security data from the Italian National Bureau of Statistics to conduct a study of all citizens over Italy aged 105 (3836 persons, 3373 women and 463 men) since January 1, 2009. It has been followed up for six years. All participants had birth certificates. At the end of the study, 2883 people died. Civil officials provided death certificates. Statistical analysis shows that the mortality rate of these very longevity Italians has not increased significantly in the past six years, stabilizing at about 50%. This indicates that the plateau period of mortality does exist for the very oldest people. The results were published in the Journal Nature on June 29.

The death rate is no longer increasing, which means that life expectancy may not reach its limit. At the end of the study, 953 elderly people who were still alive were all over 111 years old (the oldest of them was 115 years old), assuming that the mortality rate remained at 50%. Nine years later, after nine 50% trials, they would probably still be alive, approaching or surpassing the currently well-documented highest human age, Jeanne Louise Ca, a 122-year-old French woman. Lment). "If the platform period observed in this study is accurate," said Jean Marie Robine, a demographer at the French Institute of Health and Medical Sciences who was not involved in the study, "it means that there will be no limit to human life expectancy."

According to trends observed by Barbie and Agona's team, the highest life expectancy in human history may increase by one year for every doubling of the number of people reaching 105 years of age as the overall life expectancy of humans increases. According to the United Nations Population Division, there are nearly 500,000 centenarians living in the world in 2015, more than four times as many as in 1990. They predict that this number will increase eight times in the next 30 years and reach 3.7 million in 2050. Can we witness human life records being refreshed many times in our lifetime? Robin is doubtful. He said it is difficult to determine whether the Italian findings can be extended globally because the mortality plateau period in data from France, Japan and Canada, which has not yet been published, is "not so intuitive".

Why is there a decline in mortality growth and even a plateau? The hypothesis of natural selection and gene action put forward by George C. Williams, an American evolutionary biologist, provides us with an explanation. In nature, organisms with a large number of dominant genes have more reproductive opportunities, and their genes are preserved through offspring. However, many genes do not only control a single trait, the same gene has dominant characteristics in early life, but may be unfavorable to survival in late life. For example, more testosterone makes adult males stronger, more aggressive and more popular with females, but it also means that there is a higher risk of prostate cancer in later life. However, whether these polygenes can be preserved in the population depends entirely on their performance during the period of biological fertility, that is, whether they can produce offspring effectively and not be eliminated because of the threat to life in later years. So in reality, no matter human beings or other animals, when they reach the stage of old age without fertility, they are threatened by many harmless or even beneficial genes, and the mortality rate is accelerating. Over a period of time, individuals carrying these genes have died of various diseases, and the very oldest survivors rarely face the test again, so the growth of mortality has slowed or even stopped. In 2002, the Drosophila experiment conducted by Michael Rose, a professor of ecology at the University of California, Irvine, showed that the earlier fertility terminates, the earlier the plateau stage of mortality occurs, suggesting that the plateau stage phenomenon is closely related to multipotent genes.

The significance of this study by Italian scientists in exploring the limits of human life expectancy remains to be further validated by more data from other regions. In the long run, it's probably between you and me to make up enough research samples for people over 110 to live longer.

Hasn't human life reached its peak yet?:Waiting for you to sit on the sofa!


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