Nav: Home

Healthy ageing and grandmother involvement with grandchildren benefit multiple generations

February 07, 2019

Women live remarkably long after their fertility ends, but why? Researchers at the University of Turku used historical Finnish church records to show that being there after the menopause to look after grandchildren improved the grandchildren's survival. However, the study finds the ability to provide help to grandchildren declines with grandmother age and deteriorated health, and the benefits from grandmothering to our families have selected us to survive beyond menopause only up to a point.

Menopause and extended post-reproductive life separate humans from other primates, but their evolution is still a puzzle. Despite active multidisciplinary research into the limits of human lifespan brought up by recent advances in medicine and life expectancy gains, we currently know little about the limits to extended longevity in our evolutionary past.

A new study, conducted by Doctoral Candidate Simon Chapman, Postdoctoral Researchers Jenni Pettay and Mirkka Lahdenperä, and Academy of Finland Professor Virpi Lummaa from the Department of Biology at the University of Turku in Finland, used historic Finnish parish registers, which offer detailed records on the major life events of pre-industrial Finns. From these registers, they investigated the 'Grandmother Hypothesis' which proposes that the long post-reproductive lifespan in human women has evolved because grandmothers can provide help to their grandchildren. A key question for understanding why we live as long as we do - until which age grandmother presence brings benefits to their families - has not been studied before. The team therefore investigated how the presence of grandmothers of different ages and in different health affected the survival of grandchildren born between 1731 and 1890, when living conditions were still harsh and child mortality high.

Presence of maternal grandmothers was shown to increase the survival of toddlers (ages 2-5) by nearly 30%, confirming that prolonged longevity of women can be favoured by natural selection. On the other hand, grandchildren living with an old (75+) paternal grandmother had 37% lowered probability of surviving from birth to their second birthday. If the paternal grandmother was within a year of death, indicating frailty and poor health, the probability of survival was similarly lowered.

"We were a little surprised when we found that old and/or weak paternal grandmothers were actually detrimental to grandchild survival. Though we cannot say for sure what the mechanism might be, we suspect this to be the outcome of some kind of competition from living under the same roof, as the parents may have needed to split their limited resources between their dependent children and the dependent grandmother," says Chapman. The finding is really important, because it underlines the importance of remaining healthier for longer period.

According to the study, post-reproductive lifespan could indeed have evolved at least partly due to beneficial grandmother effects, but such benefits wane off with age as the opportunities and ability to provide help decline, leading to limits to the evolution of even longer lifespan. As lifespan in modern industrialised nations is much longer than in the past, it may be that medicine has allowed us to overcome the 'natural' limit on longevity.

"In that context, our finding that grandmothers in poor health were associated with higher infant mortality in the same household stresses the importance of healthy ageing and discovering ways to prolong healthy lifespan alongside the increasing total lifespan in the modern world," Chapman adds.

Grandmothers are important for the success of their families, and have been so throughout our evolutionary history. However, the frailty and health of grandmothers are of key importance not only to the grandmothers themselves, but also for the following generations. Improving the health in old age and opportunities of the elderly to stay involved with their families could benefit both the grandmothers and their families in multiple ways.
-end-
The article was published online in the Current Biology journal, and will be in a printed issue soon. Find out more about the research of the Human Life History Group at http://www.human-life-history.science

University of Turku

Related Evolution Articles:

Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Related Evolution Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...