Many modern grandmothers still adore pampering their grandchildren, take care of them and come to the aid of the parents of their offspring in difficult times. Research in recent years has shown that the "grandmother effect" plays a huge role in the survival and prosperity of offspring.
Now researchers from the UK, USA and Canada have shown that the "grandmother effect" is not only present in humans. Let us clarify that such assumptions have been put forward for more than one year, and "Vesti. Nauka" (nauka.vesti.ru) talked about this kind of research.
In anthropology and evolutionary biology, there is the so-called Grandmother hypothesis. She says that at a certain period of life for the fair sex, taking care of the offspring becomes more important than the birth of their own children. During this period, called menopause, a woman loses the ability to conceive offspring and, from the point of view of biology, becomes a real grandmother.
However, even at this age, most people lead an active lifestyle, work, perform socially significant functions, and so on.
Meanwhile, there are only four species in the wild, whose females continue to enjoy life after menopause. These are representatives of toothed whales - short-finned grinds, killer whales, narwhals and beluga whales.
Experts know that female killer whales reach menopause at the age of 30-40 years. And their life expectancy can be from 80 to 100 years. At the same time, males live several decades less and do not lose the ability to reproduce until the end of their lives.
Previously, scientists have found that postmenopausal female killer whales become the elders of the pack, store important information about the state of the environment and share it with their family group in difficult times.
Continuing observations, the same group of scientists proved that these "elderly" females focus not only on children, but also on the rest of the offspring, and in fact ensure its survival.
The team analyzed data collected over 36 years of observations from two populations of killer whales. It is specified that these populations consist of several "families", live off the Northwest Pacific coasts of Canada and the United States and feed on fish from the salmon family called Chinook salmon.
The number of both populations was more than 700 individuals, but the sample included only 378 - these were females and males with maternal grandmothers.
Using underwater cameras, biologists have identified individual killer whales for their distinctive features and tracked them as they age.
It turned out that when a particular postmenopausal grandmother died, the probability of her grandchildren dying in the next two years was 4.5 times higher when compared with cubs whose postmenopausal grandmother was still alive, and 1.5 times higher. when compared with cubs that had grandmothers who were still able to reproduce.
According to new data, females who have become grandmothers, but have not yet lost fertility, cannot provide the same level of support as postmenopausal grandmothers. The fact is that the former care more about their own children and pay less attention to their grandchildren, while the latter, becoming leaders, take responsibility for the survival of the entire large family.
These data clearly show that it is menopause that enhances the ability of grandmothers to help their offspring.
Moreover, observations have shown that the "grandmother effect" was most noticeable in killer whales during difficult times, when the number of salmon populations was declining. It was during these periods in "families" where there were no grandmothers, most of all cubs died.
The authors of the work explain that experienced and caring elderly females shared their prey with their grandchildren, and also directed the search for additional resources, which ensured the preservation of the offspring.
“Why do female killer whales stop breeding long before the end of their lives? This has been a long-standing evolutionary conundrum. Our new findings show that, like humans, postmenopausal orca grandmothers can help [survive] their offspring. This is an advantage for the family group. and it may explain why menopause developed in killer whales as well as in humans, "summarizes co-author Professor Darren Croft of the University of Exeter.
The team also believes that since the death of a grandmother can have important consequences for her "family", it may be an important factor in assessing populations in the future (especially those groups that are at risk of extinction.)
In the future, marine biologists want to observe other representatives of toothed whales to find out if they also have a "grandmother effect".
A scientific article on the results of the research is presented in the journal PNAS.