And monkeys have a middle -aged crisis

A middle -aged crisis, which people discuss a lot and not without pleasure, is characteristic, it turns out, not only to them, but also to a humanoid monkeys. This conclusion was a group of researchers from Great Britain, the USA, Japan and Germany led by Alexander Weiss, a specialist from the Scottish study group of primates and the University of Edinburgh. For several years Dr. Weiss has been studying the problems of a sense of subjective well -being in people and primates.

The subjective well -being of a person is the degree of his satisfaction with his own life, and it does not always depend on the financial situation. Numerous studies conducted by scientists of different countries show that the feeling of well -being in people changes with age: in childhood and youth it is great, then gradually decreases, reaching a minimum by 45–50 years, and then grows until old age. The exception is only the last years of life, when a person is already weak and sick. Experts investigated the situation in more than 50 countries, both developed and not very, analyzed million samples, but in all cases the curve of the dependence of subjective well-being on age has a U-shaped form. It is not possible to explain this phenomenon with social and economic reasons. Alexander Weis and his colleagues suggested that the matter is not only in economics and demography. Perhaps the “middle -aged crisis” also arose in a common ancestor of a person and monkeys, and it can be explained from a biological or evolutionary point of view.

Researchers have collected data on three different ages of monkeys. Group A consisted of 64 males and 91 female chimpanzees ( Pan TroglodyTes ) living in zoos and research centers of Japan. The age of the animals varied from 0.2 to 51.7 years. Group B included 69 males and 112 female chimpanzees from 0.4 to 56 years from 14 zoos of the United States and one Australian. Group C - 69 males and 103 females of orangutans from 1.8 to 51.2 years old, of which 89 animals are Sumatran orangutans ( Pongo Abelii ), 53 - Bornei ( pongo Pygmaeus ) and 30 - interspecific hybrids. Orangutans live in 39 zoos of the United States, Canada, Australia and Singapore.

The subjective well -being of a person is determined using a special questionnaire. Researchers adapted it to work with monkeys, as a result, four points remained in it. Employees of zoos, volunteers and researchers, familiar with their wards for at least two years and therefore able to objectively evaluate the behavior and emotional state of animals, filled out the profiles. The participants in the study were asked to evaluate the relative frequency of the good and poor mood of each monkey in points; The pleasure she receives from social contacts; The effectiveness of achieving the goal that the animal sets itself. And finally, a person had to determine how he himself liked to live a week in such conditions, be he a monkey. Each monkey was observed by several people who should not have exchanged impressions. Scientists then collected and processed all profiles.

The main results of this study are presented in the figure. Scientists found a characteristic U-shaped curve in all three groups of monkeys and in a common sample of 508 animals. Minimums of subjective well -being in different groups occur at the age of 28.3 and 27.2 years in chimpanzees and 35.4 years in orangutans. Given the life expectancy of monkeys, this period is comparable to when a middle -aged crisis occurs in people.

Researchers have proposed several hypotheses explaining the existence of a human-like U-shaped curve of well-being in anthropoids. A year earlier, Alexander Weis and his colleagues showed that Oranguta, pleased with their lives, live longer. Perhaps this is true for other primates. Less safe individuals die without reaching an venerable age, and the population of the elderly consists mainly of satisfied with life, which explains the U-shaped form of a curve of well-being. It is also possible that orangutan, chimpanzees and people skillfully avoid negative emotions, for example, choose only goals, obviously achievable at their age, shy away from unpleasant neighbors, try to fall only into pleasant situations. Researchers explain the phenomenon from an evolutionary point of view. The selection favors those animals who feel comfortable in early youth and old age, i.e. In those periods of life when they are weak and defenseless. The likelihood that such individuals and their descendants will fall into a difficult situation is less.

According to scientists, prolonged studies are needed to explain the mechanisms underlying a middle -aged crisis that would allow you to trace the indicators of the well -being of people and primates throughout their lives. They also emphasize that although a middle -aged crisis cannot be explained exclusively by economic, demographic and psychological factors, one should not discount them from accounts either.

Natalia Reznik

Alexander Weiss, James E. King, Miho Inou-Murayama, Tetsuro Matsuzawa, Andrew J. Oswald. Evidence for a Midlife Crisis in Great Apes Consistent with The U-Shape in Human Well-Being. PNAS , NOVEMBER 19, 2012 Doi : 10.1073/ PNAS .1212592109