Love Is a Good Thing: Grandmothers and Evolution

in StemSocial4 months ago

Are grandmothers a good thing? Is there any biological benefit to having a grandmother around? In the case of some species, the answer is an emphatic, "Yes." There is a hypothesis about the benefit of grandmothers, and it is called, The Grandmother Effect. This hypothesis was first formulated by British biologist Peter Medawar, in 1952.


Giraffe  Giraffa camelopardalis females 4.0.jpg
Charles J. Sharp from Sharp Photography sharpphotography. Used under CC 4.0 license.Shown in the picture is a group of female giraffes from Tswalu Kalahari Reserve, South Africa.

It was once believed that giraffes were simple animals. They had been described in the past as having no lasting bonds with their fellows. This, it turns out, is far from true. Giraffes have complex social relationships and maintain multi-generational bonds that last a lifetime. A giraffe expert from the University of Bristol explains: "evidence of...cooperative care of young and female-bonded kin groups, suggests giraffes...may actually live in a matriarchy". This recent understanding of giraffe behavior suggests that the Grandmother Effect may be a fact of giraffe society.

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Two Female Elephants, With a Calf
female elephants with a calf shankar s. from Dubai, united arab emirates 2.0.jpg
Image credit: Shankers., from Dubai. Used under CC 2.0 license. I don't know the ages of the adult elephants in the picture, but in one 2016 study, it was found that the calf of a young elephant mother was eight times more likely to survive if its grandmother lived close by. Not only do the calf's chances for survival increase when Grandma is present, but so do the chances that daughters will reproduce. The presence of a grandmother elephant appears " boost the reproductive rate of their daughters".

Both elephants and giraffes have matrilineal societies. Females form close relationships with their calves, and with other females in their group. In both giraffe and elephant societies, females live well beyond their reproductive years. The mature female, the grandmother, provides guidance, support and nurturing to the younger generations.

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YouTube Video Showing Hierarchy Among Group of Female Hyenas

"The highly matrilineal societies of spotted hyenas are unique among carnivores and closely resemble the societies of many cercopithecine (a type of monkey) primates." (From the Royal Society publishing) Hyenas live in multi-generational groups that are dominated by females. In hyena groups, inheritance includes not only a genetic transfer, but a social transfer. The offspring of a dominant female inherit her status and are groomed to behave accordingly. This is called 'social inheritance'. It has been suggested that "...traits some researchers assume to be genetic, such as the tendency to socialize and organize socially, can rather be explained by simple, social copying processes..."

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Research performed since Peter Medawar's paper (referenced at the beginning of this blog) was first published, suggests that the Grandmother Effect may be seen in a wide range of species that have matrilineal societies. An article published by a Mills College animal research scientist suggests these relationships also exist in: killer whales, lions, bonobos, and lemurs. It also exists, according to most researchers, in humans.

However, in human society, matrilineal hierarchies are rare. An article in the Journal Royal Society B: Biological Sciences explains, "Male-biased social structures predominate in human cultures, leading anthropologists to puzzle over explanations for the relatively rare societies organized around maternal kin".

Women From the Minangkabau Ethnic Group, Indonesia
Minangkabau women credit Umar Khatab 1, 2, 2.5, 3.jpg
Image credit: Umar Khatab. Used under CC 1.0o,2.0,2.5,3.0 According to anthropologist Alexander Stark, the matrilineal system of the Minangkabau has persisted throughout history.

The Grandmother Effect hypothesis arose from what biologists considered a puzzle: Why do women survive for so long after their reproductive lives have ended? Approximately one third of a woman's life is spent in non-reproductive years. The extended longevity, it is suggested, has an Evolutionary benefit. There are "indirect fitness benefits gained by grandmothers helping raise their grandchildren".(From Current Biology)

Another suggested evolutionary benefit is that grandmothers who have long lifespans bequeath that longevity to their grandchildren. The grandchildren have an increased chance of surviving, because of the Grandmother Effect, and therefore have an increased chance of passing along the genetic tendency toward long life to their own offspring.

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Lemur Group, With Suckling Young
Lemur group with young Mathias Appel public domain.jpg
Image credit: Mathias Appel. Public domain. This picture did not identify the gender of the two adults. However, researchers have observed that among ring-tailed lemurs, "...mothers are dominant over their adult daughters". Also, apparently a grandmother determines who can live in a troop and who cannot. With the death of a grandmother, it has been observed that unfavored females are evicted from the group by the new, dominant grandmother.

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A 2019 report published in the journal Current Biology looks at two studies that show the Grandmother Effect operating in human societies.

In one study, Using Geographical Distance as a Potential Proxy for Help in the Assessment of the Grandmother Hypothesis, researchers looked at a pre-industrial society to determine if proximity to the grandmother had bearing on the strength of the Grandmother Effect. Histories of multi-generational families were studied over a period of more than 150 years. The result?

Grandmother Carrying Child in Borana Ethiopia
Grandmother carrying child in Borana Ethiopia Credit Courtesy United Nations Ray Witlin public.jpg
Image credit: Ray Witlin, Courtesy of the U. N. Public domain.

Adult women who bore children while their mothers were alive produced more children over their lifespan, and successfully (more children survived) raised more children to the age of 15. The farther from their mothers these daughters lived, the less pronounced was this 'Grandmother Effect'.

Another study, Limits to Fitness Benefits of Prolonged Post-reproductive Lifespan in Women, looked at the relationship between increased age and fragility of grandmothers and benefit to grandchildren. It turns out that there is a decline in benefit with a decline in grandmothers' capacity to help. Daughters were often beyond peak reproductive years at that point, and so the loss to grandchildren would be minimal, in most cases.

Grandmother and Child, Saint Petersburg, Russia (1931--Leningrad))
grandmother and child Saint Petersburg Peterhof Palace Park credit branson DeCou public.jpg
Image credit: Branson Decou (1892-1941). Public domain.

Interestingly, some long-lived, frail, grandmothers, had a negative effect on the fitness of daughters/grandchildren. In these cases it was the paternal grandmother that had a negative effect, not the maternal grandmother. So, the matrilineal hypothesis still held up. (Mothers in law ?)

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Killer Whales

A 2019 article (Postreproductive Killer Whale Grandmothers Improve the Survival of Their Grandoffspring) published in PNAS reveals research that directly proves the existence of the Grandmother Effect in killer whales.

Killer Whale Pod in the North Pacific
whales killer Pod credit Allen Shimada NOAA punlic.jpg
Public domain.

The PNAS article states that killer whale grandmothers "increase the survival of their grandoffspring, and these effects are greatest when grandmothers are no longer reproducing". The authors of this article go on to explain that this may be one of the reasons "..killer whales have evolved the longest postreproductive life span of all nonhuman animals".

Orca (Killer Whale) Family
Orca Family gillfoto 4.0.jpg
Image credit:gillfoto. Used under CC 4.0 License.. Caption reads: "Orcas just off Pt. Louisa, Auke Rec, Juneau, Alaska".

Benefits to baby whales of having Grandma around include not only care and guidance but also extra food. It seems whale grandmothers (despite their 'killer'label) like to feed their grandoffspring. The grandmothers, "either shared their catch with the kids or helped the community find resources based on their memories..." As a matter of fact, it was noted by researchers that when a grandmother whale died, her grandoffspring were more likely to die than other whales in the pod. This effect occurred by a factor of 4.5 in the two years following the grandmother's death.

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I'm a grandmother, and I was lucky enough to have my mother with me when my children were born. In the world of science, this personal experience means nothing. But, as I look at the glowing expression of the grandmother in St. Petersburg (picture further up in this blog), I see my own mother. That's the Grandmother Effect I'm familiar with.

Is there a Grandfather Effect? Sadly, no. Not one that anyone has been able to detect, anyway. The only Grandfather Effect I was able to find had to do with the age of the grandfather at the time a child was conceived. It is suggested that the older the grandfather at the time of conception, the more likely he was to pass on the tendency for long life to his son. Unfortunately, along with this gift may come a host of genetic diseases that are associated with advanced paternal age.

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Instead of ending with that note, I'll end with a picture of adorable lemurs. These are the world's most endangered mammal. They are actually distant relatives of humans, in that lemurs and humans have a common ancestor. Lemurs are primates. They are endemic only to Madagascar.

Lemur Group, With Young
lemur catta with juvenile credit Gzen92 4.0.jpg
Image credit: Gzen92. Used under CC 4.0 license.

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@tipu curate

Thank you very much for your support!

First you write that 2 studies showed the grandmother effect in humans, but in your conclusion you write, there was no such thing detected.
To me the evolutionary benefit of grandmother´s care helping the offspring and thus increasing the overall fitness is not a "puzzle", but completely plausible and even obvious.

Grandfathers, not grandmothers. There is no Grandfather Effect, that has been detected so far, except for the possible passing on of an inclination toward longevity if the grandfather is much older when a child is conceived

Is there a Grandfather Effect? Sadly, no. Not one that anyone has been able to detect, anyway.

Grandmas rule :))

And, thank you very much for supporting my blog and for commenting. I love comments.

Oh, I see. My bad.
So are you saying, grandfathers are as useful as bee drones after reproduction? I am not (yet) a grandpa, you can be honest here :)

It appears so, but don't ask my granddaughter. She will tell you Opa is irreplaceable. And I agree :))

Fascinating! Grandmothers may also extend the juvenile period/characteristics of the young (neoteny), which is highly adventageous in complex human societies.

Thank you. And thanks for the info about neoteny. I didn't come across that, but it makes sense. Why is that good? More time to nourish and make a strong foundation for adulthood?

Yes, this variable appears to change depending on environmental pressures. The more complex the environment (new niche, variety of food sources, social changes), the more time is required for the young to reach maturity and adapt to it. In times of scarcity (simplicity), the young matures quickly so they can give birth before they die. I'm sure I'm mangling the idea, but it's something along those lines.

Interesting. I'll have to read more about that. Thanks

Excellent work. You have such a wide variety of subjects in your blogs. I always learn something new every time you post. Who doesn't love grandmothers!! This one made my day.

Thank you @pokerm. I appreciate your support and your encouragement. I work hard on the blogs and that makes it more rewarding.

I have previously heard about the grandmother effect in elephants and killer whales. In fact, for them it is even something more, because both species also have a matriarchal society, in which the oldest females are the leader, for everyone.

And it is really interesting to observe this on the example of people. And much easier. For example, it is quite obvious that the grandmother provides strong physical support in the upbringing of babies. Believe me, when my mother-in-law comes to visit, my wife and I can relax for a few hours without thinking about the child.

And the cooperation of my wife with my mother is not so strong, in terms of the child. I think this is due to the fact that she has very sharpened instincts towards her child and it is quite difficult to let "strangers" people near him. This effect works even with me. I see that my wife is calm when her mother is busy with her grandson, and I am also calm.

Thank you for the high-quality article! :)

Thank you very much for visiting and commenting.

As we look around in our own lives we can see examples. But science doesn't let us do that and draw conclusions. It's interesting when research supports our subjective impression.

Looking at my own home, my mother was invaluable in the early days of raising my children, especially my first child. I didn't know what I was doing. She probably save my son's life :))

the truth is that the love between Grandmothers and their Grandchildren cannot be under estimated. the love between these people is natural and undiluted.

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I really agree with you,I personally was brought up wt my grandmother may her soul rest in perfect peace and my the lord grant her the highest place in paradise amen.
My grandmother really take good care of me more than my mother because the love caring she give me is Perfect and awesome.

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I agree! Grandmas as the best :)

Thanks for stopping by and commenting.

You've got the wheels in my head turning
My grandmother passed when my daughter was 6 months
And my Mum about 5 years ago
That daughter of mine is 19...
I wonder what this means for her (and then I'm thinking maybe it is good that she does not care for babies, more animals - at least for now)

That was a fascinating read

Hello @kaerpediem and thank you so much for your visit.

It is true that when we read science we look at our lives and wonder how it applies. I think one of the reasons I write long science blogs is because I am seeking understanding. Especially when I read about animals, I gain insight into humans.

Writing about something means understanding it. When I write I see all my flaws in logic and have to correct my thinking. I see gaps in information and have to do more research. For me, it is great fun. And then when someone comes by, as you did, my effort is doubly rewarded.

Thank you very much for sharing your impression of my long blog. Have a most wonderful day.


Hi @agmoore the grandmother effect you explain and exemplify it very well. Now I must tell you that Grandmothers rock.

You're right, grandmas do rock. Who doesn't like Grandma :))

Thanks for reading and for commenting.

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Thank you, stemsocial. You make me feel like a colleague when you approve of my blogs. That is an elevation I do not deserve but much appreciate.

Thank you for your support.

Wow what's I saw On this is good one,the picture of animals, picture of human eg the lady's in sweet,cute gorgeous dressing Seem they are from China.
So talking about the age of elderst elephant could be so old in age,from my point of view i see why elephant have a longer life spam than other animals.due to the stature and skins so thick and heavy.

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Thank you very much for your comment. I loved writing this blog. I'm a grandma so the information really interested me :)

Who says grandmother's aren't gems.

Their presence in our lives go a long way in moulding us for the future.

The only set back may be that they are still used to the ancient ways, but all the same, grandmother's are still gems.

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I agree, grandmothers are gems. It's good to be reminded of the old ways. Slows us down a bit as we rush into the future. After all, our pasts are part of what we are. Grandmothers remind us of that.

Thanks for commenting :)

You're welcome dear.

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