Menopause it is a rare feature of terrestrial species and scientists know that it occurs in only a few. Man is one of them. Orcas and four other species of toothed whales are the rest.

A new study examines menopause in these whales, and the findings may help to understand how this biological phenomenon occurred, given that it exists in only 6 of the 6,000 species of mammals living on the planet today. It could be called: the story of the helpful grandmother-whale.

The scientists compared the lifespans of 32 toothed whale species. They found that in the five menopausal species – killer whales, killer whales, belugas, narwhals and pilot dolphins – females live about four decades longer than non-menopausal species of similar size.

A study published last year found signs of menopause among wild chimpanzees in Uganda, but this has not been documented across the species. Other odontocetes, such as blowbills and baleen whales, including the blue whale, do not go through menopause.

“This result gives us a unique insight into how menopause has evolved. Menopausal species of whales have a similar reproductive period to non-menopausal species. What differs is their life after climacteriumsaid Sam Ellis, a lecturer in animal behavior at the University of Exeter, England, and lead author of the study to be published tomorrow Wednesday in the scientific journal Nature.

With evolution, female lifespans have increased so that mothers and grandmothers can continue to support their families after their own breeding season is over, Ellis said of these whale species. “We see the same patterns in human societies, where women have a similar reproductive period to our closest relatives, the primates, but their life spans are much longer,” he explained.

Longer life spans increase the chances that female whales will help their children and grandchildren without competing with their daughters for reproduction.

“When mothers and daughters of the same group try to reproduce at the same time, there is a potential for resource conflict because both want those resources for their own offspring. The situation would worsen if the larger females bred for a longer period of time. By stopping playback, they minimize the chance of collision” said study co-author Darren Croft, a professor at the University of Exeter and executive director of the Washington State Whale Research Center.

Studies of orcas living in the Pacific off the US West Coast show that females stop reproducing around 40, but often live into their 60s or even 80s. Male orcas usually die before they reach 40. These studies have shown that orca grandmothers help their daughters and grandchildren by providing them with food, protection and, in some ways, wisdom.

“We found that cubs with a living, non-breeding grandmother have a better chance of survival than those without a grandmotherEllis said. “Other research points to a survival mechanism. In years when resources are scarce, older females lead the herd, suggesting that knowledge of their surroundings allows them to lead their family/group to resources“, he added.

These older females also catch fish and cut them in half to share the food with their family members, a behavior that is not as common in younger females — and almost non-existent in males, Ellis said.

Menopause evolved independently in humans and whales, since the last common ancestor of the two species lived 90 million years ago.

“From an evolutionary perspective, life after reproduction is difficult to explain. For most species, evolution wants females to reproduce until the end of their lives to maximize the transfer of their genes to future generationsCroft said.

“So how did menopause arise in humans and odontocetes? This new analysis shows that it arose from females extending their life span without extending their reproductive period at the same time,” Croft added. Menopause is unusual in the animal kingdom and requires an unusual set of conditions to occur. “The key is that it gives the opportunity to help close relatives in old age, at the cost of ceasing reproduction in late life“, concluded.