The importance of grandmothers in the lives of their grandchildren

October 29, 2009,

The importance of grandmothers in the lives of their grandchildren
( -- It is widely believed that women live long post-reproductive lives to help care for their grandchildren. According to the "Grandmother Hypothesis," post-menopausal women can increase their genetic contribution to future generations by increasing the survivorship of their grandchildren.

While some demographic studies have found evidence for this theory, others have found little support for it.

A team led by biological anthropologist Leslie Knapp in the Department of have discovered that a grandmother's effect on grandchildren varies according to their relatedness.

The research was carried out by a re-evaluation of the birth and death records of seven populations in Asia, North America, Europe and Africa who had lived in different periods dating back to the 17th century.

By specifically looking at in the first three years of life it was found that a grandmothers' effect on grandchildren varies according to their X-chromosome relatedness.

It was discovered that the effect of a grandmother's presence on grandchild survivorship corresponds relatively with her X-relatedness to the grandchild, which is not equivalent in boys and girls.

Specifically, maternal grandmothers have 25% X relatedness with both grandsons and granddaughters and both grandchildren are equally likely to inherit any one of her X-linked genes.

Contrastingly, paternal grandmothers will pass on one of her X chromosomes to their granddaughters (making them 50% X-related) but she will not pass this chromosome on to her grandson (making them 0% X-related).

Molly Fox, Gates Cambridge Scholar at the Department of Biological Anthropology said : "We suggest that maternal and paternal grandmothers have different incentive to invest in grandsons and granddaughters, due to differences in genetic relatedness.

"The presence of a paternal in all seven of the populations had a harmful effect on grandsons because her presence was linked with an increase in mortality.

"Meanwhile, in six out of seven populations, the paternal grandmother's presence in her granddaughter's early life had a beneficial effect in terms of the risk of mortality. This difference between paternal grandsons and granddaughters would explain a lot of the inconsistencies in previous studies, where the sex of the grandchild was not considered.

"We've only looked at child mortality, and the mechanism itself remains mysterious. Other studies have given evidence against conscious favouritism towards one grandchild or another".

It is widely believed that women live long post-reproductive lives to help care for their grandchildren and the "Grandmother Hypothesis" is based on the fact that women are genetically related to their grandchildren.The results suggest that the nature of that genetic relatedness should not be overlooked since boys and girls differ in the percent of genes they share with maternal versus paternal grandmothers based on differences in X-chromosome inheritance.

Biologists use genetic relatedness between family members to explain the evolution of not only longevity, but also altruism, kin investment, offspring recognition, parenting strategies, and tribe formation, and so reconsidering the genetic relatedness between grandmothers and grandchildren has implications throughout the field of human evolution.

Provided by University of Cambridge (news : web)

Explore further: Family ties that bind: Maternal grandparents are more involved in the lives of their grandchildren

Related Stories

The health burden of raising a grandchild

November 7, 2008

Precautionary health measures such as mammograms and cholesterol tests that identify the risk of heart disease are critical for the well-being of women over 50. Add the responsibility of providing sustained care for a grandchild, ...

Boy or girl? It's in the father's genes

December 11, 2008

( -- A Newcastle University study involving thousands of families is helping prospective parents work out whether they are likely to have sons or daughters.

Grandma and grandpa are good for children

June 4, 2008

The first national survey about the relationships that adolescents have with their grandparents shows that grandparents who are involved in the upbringing of their grandchildren can contribute to a child’s well-being.

Recommended for you

Researchers engineer a tougher fiber

February 22, 2019

North Carolina State University researchers have developed a fiber that combines the elasticity of rubber with the strength of a metal, resulting in a tougher material that could be incorporated into soft robotics, packaging ...

A quantum magnet with a topological twist

February 22, 2019

Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons ...


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Oct 29, 2009
"It is widely believed that women live long post-reproductive lives to help care for their grandchildren."

No it's not. There are a bunch of theories on why women live longer, and incidentally, most of them should probably be termed why men live shorter lives than women.

From research showing a stronger heart in older women than men, to young men's testosterone levels making them do more risky activities. Even the male body having a higher average weight and muscle mass than women, requiring more maintenance, thus a shorter life span (the same way a car driven more kilometres over the same time is more "worn out").

The grandmother hypothesis is one of the least convincing of them all, in my opinion.
5 / 5 (1) Oct 30, 2009
DonR you're confusing theories about why women live longer with theories about why we may have evolved that way.
not rated yet Oct 30, 2009
This is debatable, however, the effect of the mother-in-law on the lifespan of the husband is indisputable.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.