We know of many species in which females are able to reproduce almost to death. When they lose this ability, they die. The mystery is that in a small group of species – including humans – females survive long after they stop reproducing.
Description in “Science” the exams The study was conducted on a group of 185 females from the Ngogo community living in Kibale National Park in Uganda. Scientists tracked their fate in the years 1995-2016. They observed the same pattern they had seen in other groups of chimpanzees and in humans: the number of young a female gave birth to began to decline after the age of 30, and by age 50, the females had stopped having children. Despite this, some of them lived for many years, and some were over 60 years old at the time of their death. Research shows that females of the Ngogo group are up to 20 percent more likely to live their adult lives when they stop reproducing. This is only half the number of women in hunter-gatherer societies.
However, the most important finding was the documentation of menopause. The researchers collected urine samples from the study animals. Their analysis showed decreased levels of estrogen and progesterone and increased levels of follicle-stimulating hormone (FSH) and lyotropin (LH). Specialists were surprised by these typical signs of menopause. This means that female chimpanzees undergo the same physiological processes as female Homo sapiens, and that decreased fertility is not caused by disease, for example.
At this time, we do not know whether Njogo females are the rule or the exception. They live in an isolated environment that is better protected from human influence and the diseases they spread, as well as from other groups of chimpanzees. Furthermore, females in other chimpanzee groups are known to die shortly after the end of the reproductive stage of life. We also don’t know which conditions – those under which Njogo lives or those under other groups of chimpanzees – are more consistent with the conditions under which the animals evolved.
We now know that except for females H. Hakim I Pan caves Of the Ngogo group, females of five cetacean species also live long after they have finished breeding. Science has long grappled with the question of why females of these rare species survive many years after they stop reproducing.
One attempt to explain this phenomenon, called the grandmother hypothesis, says that older women live longer to help their daughters raise their children. newly We described Studies that seem to support this hypothesis. But the problem is, as the authors of that study pointed out, “chimpanzee grandmothers rarely do anything for their grandchildren.” Moreover, as one of the authors of the current research, anthropologist Brian Wood of the University of California, Los Angeles, has confirmed, young female chimpanzees leave their group in search of a mate, separating from their mothers. Another hypothesis that may explain the presence of menopause in Njogo females is that older females stop reproducing so as not to compete with young ones.
However, scientists are not even sure whether menopause has emerged as an adaptive feature. Some argue that its existence is a byproduct of other evolutionary processes.
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