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Researchers have proposed that menopause could be a factor in explaining the significant difference in lifespan among female whales, specifically belugas and narwhals, as they can live up to 40 years longer than other species.
Besides humans, whales are the lone mammals that experience menopause.
Only five types of toothed whales are recognized to possess this innate biological function: short-finned pilot whales, false killer whales, killer whales, narwhals, and beluga whales.
According to a study in the journal Nature, scientists have proposed that menopause may have developed in whales to allow them to live longer and become grandmothers. This may have enabled them to support their descendants by providing food and caring for the young.
According to scientists, the fact that these species are post-menopausal allows them to have extended lifespans without having to compete with their offspring for potential partners.
According to Professor Darren Croft, who is both a member of the faculty at the University of Exeter and the executive director of the Centre for Whale Research, the development of menopause and a lengthy period of life after reproductive years can only occur under particular conditions.
There must be some sort of bond between the species’s females with the next generation
Initially, a species must possess a societal arrangement where females maintain close proximity with their descendants and their descendants’ descendants. A connection between the species’ females and the future generation must exist.
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“Moreover, the women should be given the chance to assist in ways that enhance the likelihood of survival for their families.”
For instance, female toothed whales have been observed cooperating in food sharing and using their expertise to lead their group to find food when it is scarce.
The scientists used information from published studies to create a life history profile for 32 different types of whales.
The team concluded that “male menopause” did not develop in a similar manner as male whales do not exist within the same social circles as their offspring or grandchildren.
According to Professor Croft, male whales do not have the chance to help their close kin later in life. Therefore, evolution has favored them to continue reproducing until the end of their life.
Menopause and extended post-reproductive lifespan could have only occurred in particular situations.
However, this also denotes that females typically have a longer lifespan than males of their species.
According to the study, the average lifespan for female killer whales is about 80 years, while male killer whales generally die by the age of 40.
According to research, whales and humans share strikingly similar life cycles despite evolving separately for approximately 90 million years.
According to Prof Croft, prior research on killer whale populations has revealed that the life experiences of post-reproductive females play a critical role in their ability to navigate environmental difficulties during times of difficulty.
According to him, there are similar patterns in human societies, including hunter-gatherer societies, during times of drought or social conflict. In these situations, individuals seek guidance from the elders in their community who possess the necessary experience and knowledge.
“I believe it is significant to draw a comparison between humans and cetaceans in regards to the role that older female leaders, referred to as matriarchs in the case of toothed whales, or grandmothers in the case of human societies, play.”
Dr. Sam Ellis, the primary writer, from the University of Exeter, also noted that out of the 5,000 mammal species, only six go through menopause.
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“What prompted the evolution of menopause and what is the reasoning behind it?”
“Our research offers solutions to this intriguing enigma.”
The Leverhulme Trust and the Natural Environment Research Council (NERC) provided funding for the study.
Source: independent.co.uk
