The grandmother hypothesis: what is it and what does it propose about human evolution?

Let's see what the Grandmother Hypothesis is and how it tries to explain menopause.

The process of menopause is often taken as something negative and, moreover, from an evolutionary and survival point of view for the species, it could seem counterproductive.

However, research has found a number of advantages for the survival of the species, given the important role that grandmothers play in the care of grandchildren.

The grandmother hypothesis is a theory that was developed 60 years ago in order to explain a series of benefits that menopause may have from an evolutionary perspective for humans and also for other species in which this process occurs, despite the fact that, as far as is known so far, there are very few species in which menopause exists.

We will now explain what the grandmother hypothesis consists of and how it has been developed, as well as which are the other species and how it has been developed, as well as which are the other species that, besides the human being, go through the process of menopause.

What is the grandmother hypothesis?

The grandmother hypothesis is a hypothetical assumption that was developed in order to explain the role that menopause plays in human beings, from an evolutionary point of view and from the point of view of the survival of the species. of the species, since females of the human species are among the few species that go through this process, along with some cetacean species (e.g., orca, beluga whale, among others). After menopause, the process by which they stop ovulating and therefore stop being able to have more offspring, females of these species can live for decades.

That is why menopause is an unusual process in biology, since not even mammals that share the closest kinship with the human species go through this process. The females of species in which the menopause process does not occur usually have a short life expectancy from the moment they can no longer reproduce, due to the fact that their reproductive cycle is not long enough.because their reproductive cycle is usually as long as their life expectancy.

First approach to the grandmother hypothesis

In 1957, George C. Williams, an American biologist, developed a theory about menopause, postulating that this Biological process, which women go through between the ages of 45 and 55, is a process of adaptation for them.He postulated that this biological process, which women go through between the ages of 45 and 55, is an adaptation for them, because, by living several years longer, they could support their daughters and sons and help in the care of their grandchildren. This, taking into account that as human beings age, the probabilities of developing diseases increase and the remaining years of life decrease, and from an evolutionary point of view it would not be the most appropriate to have offspring at an advanced age.

Therefore, Williams postulated that elderly women can contribute to the transmission of their genes in the best possible way by helping their children and grandchildren to get ahead, instead of continuing to have children at an advanced age with the risks that this would imply.

The Williams' grandmother hypothesis was made as a proposal to explain the survival of human beings throughout history, something that must be taken into account.This is something that should be taken into account when understanding this theory, given that nowadays this theory may be somewhat obsolete. However, in the times of hunter-gatherer groups, as well as in pre-industrial times, grandmothers could collaborate in the care of grandchildren while their parents were hunting-gathering or, in later times, working.

It should be noted that this hypothesis has been developed from a biological and evolutionary perspective, given that nowadays the way of life of our species has changed considerably, since the means, the quality of life, and the quality of life of our species have changed considerably.The means, quality and life expectancy have increased, so that even the fact of having offspring or not is a choice and not a necessity to survive as a species.

Scientific support for the hypothesis

In the 1990s, the American anthropologist Kristen Hawkes investigated the importance of grandmothers in prehistoric times for the evolution of the human species, postulating that the best way to perpetuate one's own genes and, therefore, that of the species, was to support daughters in the care of grandchildren, so that they can get ahead with a greater chance of survival.

The grandmother hypothesis was investigated by Hawkes through observations he made for more than a decade with families in the village of Hada (Tanzania)who lived by gathering food and hunting, a way of life similar to that of prehistoric times. During the study they were able to observe the relevance in the development of the youngest children of the fact that grandmothers would collaborate in the collection of tubers when their grandchildren were not yet strong enough to do it themselves.

It should also be taken into account that these hypotheses were focused on remote generations, so that seen in this way, the grandmother could help to gather food for the grandchildren so that they could stay at home protected or take care of them while their mother and father went in search of food, thus helping in the survival of the grandchildren and making it easier for their daughters to give them more grandchildren.

Based on this hypothesis, Hawkes affirms that the increase in longevity in human beings was favored by the help of grandmothers. thanks to the help of grandmothers in feeding their grandchildren who no longer needed breastfeeding.In this way, the grandmother was in charge of helping with their care and feeding while the mothers were able to have the next babies earlier.

In addition, this hypothesis is based on the conjecture that grandchildren may have a longer childhood that allows for better development into adulthood thanks to the help of grandmothers in their care and in helping them to gather food or in any kind of help they could offer to their family. However, there has been no shortage of criticism of this study, blaming a lack of statistical data.

Species of animals in which it is true

When Williams developed his research in relation to his hypothesis, it was only applied to humans. However, Subsequent studies carried out by scientists from Canada and the United Kingdom were able to corroborate this hypothesis in other species, such as killer whales, and to show that in those families in which the oldest orca had died, the grandchildren of the grandmothers had more offspring..

These studies document the benefits for the survival of the species when the grandmothers cease to have the capacity to have more offspring, being able to prove that in those families in which the oldest killer whale had died, the grandchildren survived less frequently than those whose grandmothers were still alive. In addition, they also found that those older whales, who continued to have the ability to reproduce, did not provide the same support as those who had gone through the menopausal process and were more supportive.

Other studies with Asian elephants found that older females of this species help in protecting the survival of grandchildren, even though they continue to reproduce.even though they continue to reproduce.

These studies postulate that the period that grandmothers live after menopause, which is usually quite long, lasting decades in the case of humans, is very beneficial for the increase in longevity of both humans and orcas, as grandmothers help in the survival of grandchildren significantly, so that this compensates significantly the fact of not being able to have more children, all this always seen from a purely evolutionary point of view and survival as a species.