Wood, very first author of the paper, worked closely with Kevin Langergraber from Arizona State University, Jacob Negrey of University of Arizona, and Ngogo Chimpanzee Project co-directors and founders John Mitani and David Watts.
” The (study) results program that under certain environmental conditions, menopause and post-fertile survival can emerge within a social system thats quite unlike our own and includes no grandparental assistance,” Wood said, describing the grandmother hypothesis.
That hypothesis, which has actually been utilized to discuss the presence of human postmenopausal survival, proposes that females in their postreproductive years might have the ability to hand down more of their genes by assisting to raise the birth rates of their own children or by caring straight for grandchildren, thus increasing grandchildrens chances of survival.
And indeed, several research studies of human grandmas have discovered these favorable impacts. But chimpanzees have really various living arrangements than humans. Older female chimpanzees usually do not live near their children or offer look after grandchildren, yet females at Ngogo often live past their childbearing years.
Chimpanzee Life Span and Human Impact
While substantial postreproductive life periods have not formerly been observed in other long-term studies of wild chimpanzees, they have actually often been seen in chimpanzees and other primates in captivity, who get excellent nutrition and treatment. This raises the possibility that the postreproductive life expectancy of female Ngogo chimpanzees may be a short-term reaction to uncommonly beneficial environmental conditions, as this population enjoys a abundant and stable food supply and low levels of predation. Another possibility, nevertheless, is that postreproductive life expectancy are actually an evolved, species-typical quality in chimpanzees but have actually not been observed in other chimpanzee populations due to the fact that of the current unfavorable effects of humans.
” Chimpanzees are extremely susceptible to passing away from illness that come from human beings and to which they have little natural immunity,” Langergraber said. “Chimpanzee scientists, including us at Ngogo, have actually found out for many years how ravaging these illness outbreaks can be to chimpanzee populations, and how to lower their opportunities of occurring.”
A remarkable effort
The group of scientists examined mortality and fertility rates of 185 female chimpanzees from demographic information gathered from 1995 to 2016. They determined the fraction of adult life spent in a postreproductive state for all the observed women and determined hormone levels in urine samples from 66 females of differing reproductive statuses and ages, varying from 14 to 67 years.
Thousands of hours of fieldwork at Ngogo were required to gather the samples and observations needed for this study. Hormone samples were analyzed by Tobias Deschner and Melissa Emery Thompson.
” This study is the result of an extraordinary quantity of effort,” Negrey said. “Its just due to the fact that our team has spent years keeping an eye on these chimpanzees that we can be positive some females live long after theyve stopped reproducing. We likewise invested countless hours in the forest to gather urine samples from these chimpanzees with which to study hormone signals of menopause.”
The scientists measured hormonal agent levels associated with human menopause, that include increasing levels of follicle-stimulating hormone and luteinizing hormone, along with decreasing levels of ovarian steroid hormonal agents consisting of estrogens and progestins.
As with other chimpanzee populations and humans, fertility in the chimpanzees studied declined after age 30, with no births observed after age 50. The hormonal agent information showed that the Ngogo females experienced a menopausal shift similar to that of human beings, beginning around age 50.
Also like human beings, it was not uncommon for these female chimpanzees to live previous 50. A woman who maturated at age 14 was postreproductive for about one-fifth of her adult life, about half as long as a human hunter-gatherer.
” We now know that menopause and post-fertile survival emerge across a broader series of species and socio-ecological conditions than formerly valued, providing a strong basis for thinking about the functions that improved diet plans and decreased risks of predation would have played in human life history evolution,” Wood stated.
The scientists say that it will likewise be vital to track the behavior of older chimpanzees and observe how they connect with and affect other group members.
” To permit such work, it is necessary to support the long-lasting study of primates in the wild,” Wood said.
Reference: “Demographic and hormone evidence for menopause in wild chimpanzees” by Brian M. Wood, Jacob D. Negrey, Janine L. Brown, Tobias Deschner, Melissa Emery Thompson, Sholly Gunter, John C. Mitani, David P. Watts and Kevin E. Langergraber, 27 October 2023, Science.DOI: 10.1126/ science.add5473.
New research study reveals that female chimpanzees experience menopause and live beyond their reproductive years, challenging previous beliefs and providing new insights into the development of menopause in mammals. Above is a female chimpanzee from the Ngogo neighborhood in western Uganda. Older female chimpanzees usually do not live near their children or supply care for grandchildren, yet females at Ngogo frequently live past their childbearing years.
While considerable postreproductive life spans have not previously been observed in other long-lasting studies of wild chimpanzees, they have actually in some cases been seen in chimpanzees and other primates in captivity, who receive good nutrition and medical care. Another possibility, however, is that postreproductive life spans are in fact a progressed, species-typical trait in chimpanzees but have not been observed in other chimpanzee populations due to the fact that of the recent unfavorable impacts of people.
New research study reveals that female chimpanzees experience menopause and live beyond their reproductive years, challenging previous beliefs and providing new insights into the development of menopause in mammals. Above is a female chimpanzee from the Ngogo neighborhood in western Uganda. Credit: The Ngogo Chimpanzee Project
Research on the Ngogo community in Uganda exposes that humans human beings arent the only primates with long post-fertile life stage.
A team of scientists has actually been studying the Ngogo neighborhood of wild chimpanzees in Ugandas Kibale National Park for over twenty years. Their current publication in the journal Science reveals that female chimpanzees in this population can experience menopause and have a postreproductive life expectancy.
Prior to the study, these traits had actually only been found among mammals in a few species of toothed whales, and among primates– only in humans. These new market and physiological data can assist researchers better understand why menopause and post-fertile survival occur in nature, and how it developed in the human species.
The Role of Post-Menopausal Females in Society
” In societies worldwide, females past their childbearing years play crucial functions, both economically and as wise consultants and caretakers,” said Brian Wood, UCLA associate professor of sociology. “How this life history evolved in humans is a fascinating yet tough puzzle.”