The Grandmother Hypothesis: What It Is And What It Proposes About Human Evolution
The process of menopause is often taken as something negative and, furthermore, from an evolutionary and survival point of view for the species it could seem counterproductive.
However, research has been carried out in this regard that has found a series of advantages for the survival of the species, given the important role that grandmothers play in caring for grandchildren.
The grandmother hypothesis is a theory that was developed 60 years ago in order to explain a series of benefits that menopause can have from an evolutionary perspective for humans and also for other species in which this process occurs, to Although, as far as is known, there are very few species in which menopause exists.
Next we will explain what the grandmother hypothesis consists of and how it has developed, as well as which are the other species that, in addition to humans, go through the menopause process.
Grandma’s hypothesis is a hypothetical assumption that was developed in order to explain the role that menopause plays in humans, from an evolutionary and survival point of view of the species, since the females of the human species are among the few species that go through this process, along with some species of cetaceans (e.g., the killer whale, the beluga, among others). After menopause, a process by which they stop ovulating and, therefore, being able to have more offspring, females of these species can live for decades.
This is why menopause is an unusual process in biology, given that not even the mammals that share the greatest relationship with the human species go through this process. 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 because their reproductive cycle is usually as long as their life expectancy.
In 1957, George C. Williams, an American biologist, developed a theory about menopause, postulating that this biological process that women go through between approximately 45 and 55 years of age represents an adaptation for them, because, by living several more years, they could support their daughters and sons and help care for their grandchildren. This, taking into account that when 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 older 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 entails. would imply.
The Williams’ grandmother’s hypothesis was made as a proposal to explain the survival of human beings throughout history, something that must be taken into account when understanding this theory, given that currently this theory may be somewhat obsolete. However, in the era of hunter-gatherer groups, as well as in pre-industrial times, grandmothers could help care for grandchildren while their parents were hunting-gathering or, in later times, working.
It should be noted that this hypothesis It has been developed from a biological and evolutionary perspective, given that today the way of life of our species has changed significantly since the means, quality and expectancy of life 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 90s of the 20th century, the North American anthropologist Kristen Hawkes investigated the importance that grandmothers had in prehistory in favor of the evolution of the human species, postulating that the best way to perpetuate one’s own genes and, therefore, Therefore, that of the species, was supporting daughters in caring for grandchildren, so that they can get ahead with a greater probability of surviving.
The grandmother hypothesis was investigated by Hawkes through observations he made for more than a decade with families in the town of Hada (Tanzania), who lived by gathering food and hunting, a way of life similar to that of prehistory. During the study they were able to observe the relevance that the fact that grandmothers collaborated in collecting tubers when their grandchildren were not yet strong enough to do it themselves had on the development of the youngest children.
It must also be taken into account that these hypotheses were focused on remote generations, so that seen this way, the grandmother could help collect food for the grandchildren so that they could be at home protected or take care of them while their mother and father went looking for of food, so this helped in the survival of the grandchildren and made it easier for their daughters to give them more grandchildren.
Based on this hypothesis, Hawkes affirms that the increase in longevity in humans was favored thanks to the help of grandmothers in feeding grandchildren who no longer needed breastfeeding so the grandmother was in charge of helping with their care and feeding while the mothers could have the following babies sooner.
Furthermore, this hypothesis is based on the conjecture that grandchildren may have a longer childhood that allows better development towards adulthood thanks to the help of grandmothers in their care and in helping to collect food or in any other way. type of help they could offer their family. However, there has been no shortage of criticism of this study, blaming a lack of statistical data.
When Williams developed his research in relation to his hypothesis, it was only applied to human beings. However, Subsequent studies carried out by scientists from Canada and the United Kingdom were able to corroborate this hypothesis in other species, such as the orcas
These studies document the benefits for the survival of the species when grandmothers no longer have the capacity to have more offspring, and can verify that in those families in which the oldest orca had died, grandchildren survived less frequently than those whose grandmothers They were still alive. In addition, they were also able to verify that those older whales, which continued to have the ability to reproduce, did not provide the same support as those that had gone through the menopause process, which provided greater support.
Other studies with the Asian elephant found that older females of this species help protect the survival of their grandchildren even though they continue to reproduce.
These studies postulate that the period that grandmothers live after menopause, which is usually quite long, and can last decades in the case of human beings, is very beneficial for increasing the longevity of both humans and orcas. , since grandmothers help in the survival of grandchildren significantly, so that this significantly compensates for the fact of not being able to have more children, all of this always seen from a purely evolutionary point of view and survival as a species.
