Nana's R Powah!
Oct. 27th, 2007 10:18 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
semiotic_pirateIn some cultures all women over a certain age are, indeed, called grandmother and they are accorded a certain respect within the society due to their accumulated knowledge. They are the mothers - the ones from whom we have all come - the ones that (in a tribal society) helped to raise us all... Regardless of actual blood ties. Fairy tales are VERY adamant about the way we are to treat old women, and the consequences of actions that deviate from this way. I happen to LOVE the way Mercedes Lackey has worked this into her Fairy Godmother series of stories.
The following two, connected stories are from the New York Times. a link to Kristen Hawkes' web-page at the University of Utah is provided. Her web-page links to various articles & studies she has written for peer-reviewed journals that are relevant to this story. Below that is a follow-up article to the first article, based on a lively comment/discussion about the impact of grandmothers on the lives of various individuals... As well as some bitch-slapping and whining concerning the role of grandpas. I'm sure the original set of comments had some flame-wars occurring.
Evolution’s Secret Weapon: Grandma
Juana Luis, 78, guards a rice field in the Philippines against birds. One theory suggests the work of older women may have provided humans with a survival advantage. (Jay Directo/AFP/Getty Images)
Are grandmothers an evolutionary necessity? The contributions of older women to society have long been debated by anthropologists. In the animal world, females often don’t live much past their reproductive years. But in our world, women live into their 80s and beyond — a fact that may be explained, in part, by evolutionary forces.
“It’s the norm in human population that women are vigorous and productive long past their fertility,’’ noted Kristen Hawkes, an anthropologist at the University of Utah. She spoke yesterday at the North American Menopause Society meeting in Dallas.
Today many women feel marginalized once they reach menopause. But research suggests that far from being a burden to societies, grandmothers have played an important role in the evolution of human longevity. Studies of modern hunter-gatherers in Tanzania, Venezuela and Eastern Paraguay — societies that offer insights into how humans evolved — consistently show that Grandma is doing much of the work.
Researchers have even measured the muscle strength of men and women in these communities and weighed the baskets and bundles carted around by them. Often, the scientists find, women in their 60s are as strong as women in their 20s. “It’s the women over 40 who are carrying the heavy loads,’’ said Dr. Hawkes.
The research is the basis for the grandmother hypothesis (see below) that may help explain why menopause occurs. The basic idea is that an end to a woman’s reproductive years allows her to channel her energy and resources into caring for her children and grandchildren, thereby providing her descendants with a survival advantage.
Until recently, many researchers argued that menopause isn’t natural and that modern medicines simply have increased life expectancy well beyond what nature intended. But while it’s true that the average life expectancy for women was just 40 years only a century ago, recent studies have found the number was skewed by high infant mortality rates at the time. Plenty of women were living well past age 40, Dr. Hawkes said. Even the Bible recognized that women can live well beyond their fertile years, NAMS executive director Dr. Wulf Utian noted.
In hunter-gatherer cultures today, said Dr. Hawkes, “women are strong and economically productive into their 60s….Women are not being helped along by others. The flow of help is going into the other direction.”
Grandmother Hypothesis
Theorists See Evolutionary Advantages In Menopause
By NATALIE ANGIER
The Hadza people of northern Tanzania are a small group of hunter-gatherers who share a language, a culture and a distaste for gardening. Time and again, government and church agencies have sought to transmute them into full-time farmers, but the Hazda have always returned to the bush, where they subsist on wild goods like fruits, honey, tubers and game. The terrain is hard and hilly, and so is the life, but on one incomparable resource the foragers can always rely: a pack of old ladies with hearts like young horses.
As Dr. Kristen Hawkes of the University of Utah and her colleagues have found in their extensive studies of the Hadza, women in their 50's, 60's, 70's and beyond are among the most industrious members of the group. They are out in the woods for seven or eight hours a day, gathering more food than virtually any of their comrades.
When a young woman is burdened with a suckling infant and cannot fend for her family, she turns for support, not to her mate, but to a senior female relative -- her mother, an aunt, an elder cousin. It is Grandma, or Grandma-proxy, who keeps the woman's other children in baobab and berries, Grandma who keeps them alive. She is not a sentiment, she is a requirement. As Dr. Hawkes, Dr. James O'Connell of the University of Utah and Dr. Nicholas Blurton Jones of the University of California at Los Angeles report in the latest issue of Current Anthropology, a nursing Hadza woman always has a postmenopausal helper.
There are only about 750 Hadza, and they are contemporary hunter-gatherers, not pristine relics of prelapsarian humanity. Nevertheless, the centrality of elder women to their group's survival has thrown fresh kindling on the spirited debate over the origins and purpose of human menopause.
As doctors and women thrash out the best way to "treat" menopause, pitting the benefits of estrogen therapy to the heart and bones against the risks the hormone poses to the breast and possibly the ovaries, evolutionary scientists address the menopause mystery from a more high-flown, though no less quarrel-prone, perspective. They ask whether menopause is an ancient adaptation or a contemporary artifact. Is it the well-wrought product of natural selection, or the incidental byproduct of an unnaturally prolonged life span?
Proponents of the adaptationist camp generally see menopause as the thriftiest solution to the problem of exorbitant offspring. By this view, the ludicrous amount of time required for a mother to rear children to maturity led to the need for so-called premature reproductive senescence, an early retirement program for the ovaries. Through the mechanism of menopause, an ancestral woman theoretically was spared the risks of childbirth, and thus had a heightened chance of living long enough to see her existing children out the door. Dr. Jared Diamond, a physiologist at the University of California at Los Angeles Medical School has said that menopause, like big brains and upright posture, is "among the biological traits essential for making us human."
The artifactualists insist that prehistoric women almost never survived past the age of 30, let alone long enough to experience the thrill of hot flashes. By their reckoning, menopause is a modern luxury, the result of women now outlasting an egg supply that more than sufficed for the cameo appearances that their Stone Age foremothers called lives. "For most of our existence, we simply didn't live very long," said Dr. Alison Galloway, an anthropologist at the University of California at Santa Cruz. "Menopause happens because, through technology, we've extended our lives to the point where we run out of egg follicles. There's nothing beneficial about it."
Dr. Hawkes lends a new spin to the debate, combining elements of each camp and adding a few bold spirals of her own. She agrees with the artifactualists that menopause per se is not an adaptation -- it is not the product of selective design. A woman's ovaries do not shut down "prematurely," she says. They last 40 or 45 years, the same time as the ovaries of our close relatives, chimpanzees and gorillas. In a sense, she says, women do outlive their egg supply, which is fixed before birth and cannot be added to, as men continuously generate new sperm.
On the other hand, Dr. Hawkes concurs with the adaptationists that prehistoric women very likely often survived past menopause, and that they were instrumental to the survival of their families. She goes further. Only with the ascent of the grandmother, she says, were human ancestors freed to exploit new habitats, to go where no other hominid or primate had gone before, and to become the species we know so well.
"The Grandmother Hypothesis gives us a whole new way of understanding why modern humans suddenly were able to go everywhere and do everything," Dr. Hawkes said. "It may explain why we took over the planet."
In another new study that touches on the evolutionary basis of menopause and maternal longevity, Dr. Thomas Perls of Harvard Medical School and his colleagues describe in the current issue of Nature their finding that women who lived to be at least 100 years of age were much likelier to have remained fruitful well into middle age than a comparable group of women who died at the age of 73. Looking at two sets of women born in 1896 who were equivalent in race, religion and other factors but who differed in their life spans, the researchers found that among the 54 women who died in 1969 at the age of 73, only 5.5 percent had given birth in their 40's. By comparison, 19.5 percent of the centenarians had children after 40, one of them at age 53.
Because the women in Dr. Perls's analysis all had their families before the rise of fertility-enhancing technology, the researchers see the stark discrepancy in maternal stamina between the two groups as evidence of innate selective drives at work. They propose that the genes allowing the centenarians to stay fruitful for an exceptionally long time continued working long after menopause to lengthen the women's life spans, supporting the view that a woman's extended survival is indeed crucial to her offsprings' prospects.
The older a woman is at last birth, the more years she must stick around to keep her family afloat. (The researchers also believe that menopause, the complete cessation of fertility, evolved to prevent aging women from dying in childbirth while they still had dependent young, but their analysis of the centenarians offers no direct proof of that.)
The notion that menopause has adaptive value for women and their offspring is itself getting a bit long in tooth. Dr. George C. Williams, a renowned evolutionary biologist, first proposed it in 1957 to explain the seemingly anomalous nature of human menopause. Other female primates, and even species like fin whales and elephants that live into their 80's, can continue bearing young to the bitter end, he pointed out.
Why are humans different? And why does menopause occur universally among women, and during a short window of time -- at the half-century mark, give or take four years -- while other depradations of age, like gray hair or presbyopia, occur gradually and randomly? Dr. Williams saw in menopause the thumbprint of natural selection, and suggested that the early cessation of reproduction paradoxically enhanced a woman's reproductive "fitness," by assuring that she lived long enough to see her children bear children themselves
-- that she became a grandmother.
Others have picked up and expanded on the rudimentary Grandmother Hypothesis. Dr. Diamond has proposed that aging women, and men, were repositories of essential information in preliterate times, living libraries for their clans, able to distinguish edible from poisonous plants and to recall events of long ago that remained pertinent to survival.
In traditional societies, clan members are often related, and so by aiding the tribe the elders help themselves. Only women need protection from the hazards of advanced maternity, Dr. Diamond says, and so only women need to undergo premature reproductive senescence to keep them around for the benefit of their kin.
Yet efforts to demonstrate the adaptive value of menopause have proved elusive. Dr. Kim Hill and Dr. Magdalena Hurtado, anthropologists at the University of New Mexico, spent years studying the Ache, a group of hunter-gatherers living in eastern Paraguay. They tried to estimate the impact of postmenopausal women on the welfare of their children and grandchildren, to see if the presence of a grandmother had a measurable effect, for example by reducing the mortality of grandchildren.
The anthropologists concluded that the Ache grandmothers did not make enough of a cumulative difference to their families to justify, in Darwinian terms, the loss through menopause of their own reproductive capacity.
Using mathematical models, Dr. Alan Rogers of the University of Utah estimated that a postmenopausal woman would have to double the number of children her children bore, and eliminate infant mortality among those grandchildren, to make menopause look like a sound strategy for propagating one's genes. That is not a grandmother -- that is Neutron Nana.
"Adaptive menopause is an interesting idea, and I'm trying to keep an open mind," said Dr. Steven N. Austad, a professor of zoology at the University of Idaho in Moscow and author of "Why We Age" (John Wiley & Sons, 1997). "But I just don't see evidence to support it."
Before anybody consigns the Grandmother Hypothesis to a conceptual nursing home, however, Dr. Hawkes and her colleagues offer evidence in the Hadza study that elder women can make an enormous, and quantifiable, difference to their kin. The researchers found that whenever the mother of young children gave birth to a new baby and was absorbed by the rigors of breast-feeding, it was only through the intervention of a senior female relative that the older children's weight stayed up. And the harder the elders foraged, the higher the numbers on the researchers' bathroom scale.
Importantly, the elder Hadza women were flexible in how they apportioned their assistance. If a woman could help her nursing daughter, she did. If she had no daughter, she helped a niece, or a cousin once removed.
Dr. Hawkes pointed out that in the Ache study showing little benefit from grandma, the researchers had focused on the relationships between mothers, their children and their children's children. Dr. Hawkes and her colleagues were more inclusive in their analysis. "If we restricted ourselves to counting the reproductive success only of women whose moms were still alive, we'd underestimate the effect of help from senior women by a huge amount," Dr. Hawkes said. "And you expect, with strategic critters like ourselves, that natural selection would favor adjusting help to where it was needed most."
Dr. Hawkes proposes that what distinguishes a human female from her chimpanzee or gorilla cousins is not that the woman goes through menopause and the chimpanzee does not, but rather that the chimpanzee, at 45 and with ovaries failing, is globally decrepit and close to death, while a woman can live decades after follicular fadeout.
But young chimpanzees do not need elder females to help them. Once they are weaned, they feed themselves, and so there are no selective pressures to keep Aunt Chimsky alive. Only human children are fed for years after leaving the breast, and a senior female can serve up nuts and berries as well as can a mother, and better when mother is lactating.
Dr. Hawkes and her co-workers suggest that the extension of life past menopause was a watershed event in human prehistory. With a labor force of elder females available to help provision the young, adults were then free to colonize new territories unavailable to those primates that did not provision their weaned young, and that were thus restricted to feeding grounds where the pickings were easy enough for juvenile fingers. Suddenly humans could migrate to places where it required full adult strength and cunning to extract food. They could go wherever they pleased. After all, there were older women around to help.
Supporting this proposition are the foraging patterns of the Hadza. Very young children find much of their food themselves, but they depend on adults for half their calories, and those calories come from foods, like deeply buried tubers, that only an adult can obtain. Growing old, then, may be nothing new, and the postmenopausal years worthy of celebration and gratitude. Grandma is great, she is strong, and she baby-sits for free.
-----------------------------------------------------
Grandma, revisited
My recent article about the evolutionary role of grandmothers generated a lively discussion on the message boards. Many readers used the story as an opportunity to celebrate their own grandmothers. Here’s what two of them had to say.
Grandmothers are incredible. My maternal grandmother taught me to play baseball and football (I can still hear her shout, “Hit him in the numbers!”) and introduced me to pro wresting, poker and craps. The other grandmother, a self-reliant farm woman, introduced me to the wonderful world of nature and the great outdoors. The maternal grandmother was such an unforgettable character, all the women I was attracted to — woe begone! — later in life were very, very much like her. — Posted by Charles Downey
I had two wonderful grandmothers and thought of them as I read this. One survived all her children and the other survived all but one and lived to be 103. Both of these women were terrific role models and certainly fit the picture of grandmothers helping younger members of the family - emotionally and physically. I also thought of my daughters now entering menopause, active and vibrant women a little troubled by this change. If we continue to refer to menopause as ‘the change,’ let’s make sure we understand and give voice to the knowledge that it’s a positive change! — Posted by Molly
Several readers were insulted by the notion that scientists saw fit to develop an evolutionary theory about women after their reproductive years.
Why do we need scientific studies to validate that women are valuable even when they cannot reproduce? The implicit assumption in all this is that a woman’s purpose is to reproduce, and it’s necessary to find a reason for her to survive past her childbearing years….A productive person is important to society at large no matter where she is on her life continuum. We are worthwhile because we are human, not because we’re useful to evolution. — Posted by N.W. Clerk
Others were bothered by the fact that my story suggested Grandma is doing a disproportionate share of the work.
Why are we celebrating the fact that 60-year-old women are working as hard as 20 year olds? How does that imply status or respect? What are the 60-year-old men doing? Since most traditional societies are patriarchal, I bet they are enjoying their status as elders who no longer have to toil to maintain their place in the family. — Posted by T.K. Hicks
And finally, some readers noted that for many grandchildren, grandma is only half the story.
Not to take anything away from grandmothers but let us not overlook grandpa’s acquired wisdom. — Posted by joe fox
------------------------------------------
One of the losses that an industrialized culture experiences is the demise of the multigenerational family structure, the support systems inherent in that structure. We gain, however, chosen communities and families - that may consist of various generations. There are pros and cons to each structure... Think about it. Talk about it.
BTW: Joe? By taking the time to make your comment, and making us take time away from thinking about grandma... you are indeed taking something away from the grandmothers. A discussion about a marginalized group is always having something taken away from it when people bring in comments about the non-marginalized group. Grandfathers, in a patriarchal society, have had many many studies done about them... they are inevitably referred to as "elders." Perhaps we should de-gender our language completely when referring to people as a group? Both men and women of the grandparent persuasion can be referred to as elders? Only if they both carry out the same duties in their roles as they serve society. We are all servants (and owners) of society, we are referred to as citizens. But... elders are still citizens, right? Are we taking something away from them by not including that in their title? See how much this train of thought has derailed the original discussion? It is about the historical, evolutionary induced, role of elderly females on their culture and survival. This is NOT a discussion on anything else, especially not the impact of this evolutionary heritage on today's culture and survival... Right?
The following two, connected stories are from the New York Times. a link to Kristen Hawkes' web-page at the University of Utah is provided. Her web-page links to various articles & studies she has written for peer-reviewed journals that are relevant to this story. Below that is a follow-up article to the first article, based on a lively comment/discussion about the impact of grandmothers on the lives of various individuals... As well as some bitch-slapping and whining concerning the role of grandpas. I'm sure the original set of comments had some flame-wars occurring.
Evolution’s Secret Weapon: Grandma
Juana Luis, 78, guards a rice field in the Philippines against birds. One theory suggests the work of older women may have provided humans with a survival advantage. (Jay Directo/AFP/Getty Images)
Are grandmothers an evolutionary necessity? The contributions of older women to society have long been debated by anthropologists. In the animal world, females often don’t live much past their reproductive years. But in our world, women live into their 80s and beyond — a fact that may be explained, in part, by evolutionary forces.
“It’s the norm in human population that women are vigorous and productive long past their fertility,’’ noted Kristen Hawkes, an anthropologist at the University of Utah. She spoke yesterday at the North American Menopause Society meeting in Dallas.
Today many women feel marginalized once they reach menopause. But research suggests that far from being a burden to societies, grandmothers have played an important role in the evolution of human longevity. Studies of modern hunter-gatherers in Tanzania, Venezuela and Eastern Paraguay — societies that offer insights into how humans evolved — consistently show that Grandma is doing much of the work.
Researchers have even measured the muscle strength of men and women in these communities and weighed the baskets and bundles carted around by them. Often, the scientists find, women in their 60s are as strong as women in their 20s. “It’s the women over 40 who are carrying the heavy loads,’’ said Dr. Hawkes.
The research is the basis for the grandmother hypothesis (see below) that may help explain why menopause occurs. The basic idea is that an end to a woman’s reproductive years allows her to channel her energy and resources into caring for her children and grandchildren, thereby providing her descendants with a survival advantage.
Until recently, many researchers argued that menopause isn’t natural and that modern medicines simply have increased life expectancy well beyond what nature intended. But while it’s true that the average life expectancy for women was just 40 years only a century ago, recent studies have found the number was skewed by high infant mortality rates at the time. Plenty of women were living well past age 40, Dr. Hawkes said. Even the Bible recognized that women can live well beyond their fertile years, NAMS executive director Dr. Wulf Utian noted.
In hunter-gatherer cultures today, said Dr. Hawkes, “women are strong and economically productive into their 60s….Women are not being helped along by others. The flow of help is going into the other direction.”
Grandmother Hypothesis
Theorists See Evolutionary Advantages In Menopause
By NATALIE ANGIER
The Hadza people of northern Tanzania are a small group of hunter-gatherers who share a language, a culture and a distaste for gardening. Time and again, government and church agencies have sought to transmute them into full-time farmers, but the Hazda have always returned to the bush, where they subsist on wild goods like fruits, honey, tubers and game. The terrain is hard and hilly, and so is the life, but on one incomparable resource the foragers can always rely: a pack of old ladies with hearts like young horses.
As Dr. Kristen Hawkes of the University of Utah and her colleagues have found in their extensive studies of the Hadza, women in their 50's, 60's, 70's and beyond are among the most industrious members of the group. They are out in the woods for seven or eight hours a day, gathering more food than virtually any of their comrades.
When a young woman is burdened with a suckling infant and cannot fend for her family, she turns for support, not to her mate, but to a senior female relative -- her mother, an aunt, an elder cousin. It is Grandma, or Grandma-proxy, who keeps the woman's other children in baobab and berries, Grandma who keeps them alive. She is not a sentiment, she is a requirement. As Dr. Hawkes, Dr. James O'Connell of the University of Utah and Dr. Nicholas Blurton Jones of the University of California at Los Angeles report in the latest issue of Current Anthropology, a nursing Hadza woman always has a postmenopausal helper.
There are only about 750 Hadza, and they are contemporary hunter-gatherers, not pristine relics of prelapsarian humanity. Nevertheless, the centrality of elder women to their group's survival has thrown fresh kindling on the spirited debate over the origins and purpose of human menopause.
As doctors and women thrash out the best way to "treat" menopause, pitting the benefits of estrogen therapy to the heart and bones against the risks the hormone poses to the breast and possibly the ovaries, evolutionary scientists address the menopause mystery from a more high-flown, though no less quarrel-prone, perspective. They ask whether menopause is an ancient adaptation or a contemporary artifact. Is it the well-wrought product of natural selection, or the incidental byproduct of an unnaturally prolonged life span?
Proponents of the adaptationist camp generally see menopause as the thriftiest solution to the problem of exorbitant offspring. By this view, the ludicrous amount of time required for a mother to rear children to maturity led to the need for so-called premature reproductive senescence, an early retirement program for the ovaries. Through the mechanism of menopause, an ancestral woman theoretically was spared the risks of childbirth, and thus had a heightened chance of living long enough to see her existing children out the door. Dr. Jared Diamond, a physiologist at the University of California at Los Angeles Medical School has said that menopause, like big brains and upright posture, is "among the biological traits essential for making us human."
The artifactualists insist that prehistoric women almost never survived past the age of 30, let alone long enough to experience the thrill of hot flashes. By their reckoning, menopause is a modern luxury, the result of women now outlasting an egg supply that more than sufficed for the cameo appearances that their Stone Age foremothers called lives. "For most of our existence, we simply didn't live very long," said Dr. Alison Galloway, an anthropologist at the University of California at Santa Cruz. "Menopause happens because, through technology, we've extended our lives to the point where we run out of egg follicles. There's nothing beneficial about it."
Dr. Hawkes lends a new spin to the debate, combining elements of each camp and adding a few bold spirals of her own. She agrees with the artifactualists that menopause per se is not an adaptation -- it is not the product of selective design. A woman's ovaries do not shut down "prematurely," she says. They last 40 or 45 years, the same time as the ovaries of our close relatives, chimpanzees and gorillas. In a sense, she says, women do outlive their egg supply, which is fixed before birth and cannot be added to, as men continuously generate new sperm.
On the other hand, Dr. Hawkes concurs with the adaptationists that prehistoric women very likely often survived past menopause, and that they were instrumental to the survival of their families. She goes further. Only with the ascent of the grandmother, she says, were human ancestors freed to exploit new habitats, to go where no other hominid or primate had gone before, and to become the species we know so well.
"The Grandmother Hypothesis gives us a whole new way of understanding why modern humans suddenly were able to go everywhere and do everything," Dr. Hawkes said. "It may explain why we took over the planet."
In another new study that touches on the evolutionary basis of menopause and maternal longevity, Dr. Thomas Perls of Harvard Medical School and his colleagues describe in the current issue of Nature their finding that women who lived to be at least 100 years of age were much likelier to have remained fruitful well into middle age than a comparable group of women who died at the age of 73. Looking at two sets of women born in 1896 who were equivalent in race, religion and other factors but who differed in their life spans, the researchers found that among the 54 women who died in 1969 at the age of 73, only 5.5 percent had given birth in their 40's. By comparison, 19.5 percent of the centenarians had children after 40, one of them at age 53.
Because the women in Dr. Perls's analysis all had their families before the rise of fertility-enhancing technology, the researchers see the stark discrepancy in maternal stamina between the two groups as evidence of innate selective drives at work. They propose that the genes allowing the centenarians to stay fruitful for an exceptionally long time continued working long after menopause to lengthen the women's life spans, supporting the view that a woman's extended survival is indeed crucial to her offsprings' prospects.
The older a woman is at last birth, the more years she must stick around to keep her family afloat. (The researchers also believe that menopause, the complete cessation of fertility, evolved to prevent aging women from dying in childbirth while they still had dependent young, but their analysis of the centenarians offers no direct proof of that.)
The notion that menopause has adaptive value for women and their offspring is itself getting a bit long in tooth. Dr. George C. Williams, a renowned evolutionary biologist, first proposed it in 1957 to explain the seemingly anomalous nature of human menopause. Other female primates, and even species like fin whales and elephants that live into their 80's, can continue bearing young to the bitter end, he pointed out.
Why are humans different? And why does menopause occur universally among women, and during a short window of time -- at the half-century mark, give or take four years -- while other depradations of age, like gray hair or presbyopia, occur gradually and randomly? Dr. Williams saw in menopause the thumbprint of natural selection, and suggested that the early cessation of reproduction paradoxically enhanced a woman's reproductive "fitness," by assuring that she lived long enough to see her children bear children themselves
-- that she became a grandmother.
Others have picked up and expanded on the rudimentary Grandmother Hypothesis. Dr. Diamond has proposed that aging women, and men, were repositories of essential information in preliterate times, living libraries for their clans, able to distinguish edible from poisonous plants and to recall events of long ago that remained pertinent to survival.
In traditional societies, clan members are often related, and so by aiding the tribe the elders help themselves. Only women need protection from the hazards of advanced maternity, Dr. Diamond says, and so only women need to undergo premature reproductive senescence to keep them around for the benefit of their kin.
Yet efforts to demonstrate the adaptive value of menopause have proved elusive. Dr. Kim Hill and Dr. Magdalena Hurtado, anthropologists at the University of New Mexico, spent years studying the Ache, a group of hunter-gatherers living in eastern Paraguay. They tried to estimate the impact of postmenopausal women on the welfare of their children and grandchildren, to see if the presence of a grandmother had a measurable effect, for example by reducing the mortality of grandchildren.
The anthropologists concluded that the Ache grandmothers did not make enough of a cumulative difference to their families to justify, in Darwinian terms, the loss through menopause of their own reproductive capacity.
Using mathematical models, Dr. Alan Rogers of the University of Utah estimated that a postmenopausal woman would have to double the number of children her children bore, and eliminate infant mortality among those grandchildren, to make menopause look like a sound strategy for propagating one's genes. That is not a grandmother -- that is Neutron Nana.
"Adaptive menopause is an interesting idea, and I'm trying to keep an open mind," said Dr. Steven N. Austad, a professor of zoology at the University of Idaho in Moscow and author of "Why We Age" (John Wiley & Sons, 1997). "But I just don't see evidence to support it."
Before anybody consigns the Grandmother Hypothesis to a conceptual nursing home, however, Dr. Hawkes and her colleagues offer evidence in the Hadza study that elder women can make an enormous, and quantifiable, difference to their kin. The researchers found that whenever the mother of young children gave birth to a new baby and was absorbed by the rigors of breast-feeding, it was only through the intervention of a senior female relative that the older children's weight stayed up. And the harder the elders foraged, the higher the numbers on the researchers' bathroom scale.
Importantly, the elder Hadza women were flexible in how they apportioned their assistance. If a woman could help her nursing daughter, she did. If she had no daughter, she helped a niece, or a cousin once removed.
Dr. Hawkes pointed out that in the Ache study showing little benefit from grandma, the researchers had focused on the relationships between mothers, their children and their children's children. Dr. Hawkes and her colleagues were more inclusive in their analysis. "If we restricted ourselves to counting the reproductive success only of women whose moms were still alive, we'd underestimate the effect of help from senior women by a huge amount," Dr. Hawkes said. "And you expect, with strategic critters like ourselves, that natural selection would favor adjusting help to where it was needed most."
Dr. Hawkes proposes that what distinguishes a human female from her chimpanzee or gorilla cousins is not that the woman goes through menopause and the chimpanzee does not, but rather that the chimpanzee, at 45 and with ovaries failing, is globally decrepit and close to death, while a woman can live decades after follicular fadeout.
But young chimpanzees do not need elder females to help them. Once they are weaned, they feed themselves, and so there are no selective pressures to keep Aunt Chimsky alive. Only human children are fed for years after leaving the breast, and a senior female can serve up nuts and berries as well as can a mother, and better when mother is lactating.
Dr. Hawkes and her co-workers suggest that the extension of life past menopause was a watershed event in human prehistory. With a labor force of elder females available to help provision the young, adults were then free to colonize new territories unavailable to those primates that did not provision their weaned young, and that were thus restricted to feeding grounds where the pickings were easy enough for juvenile fingers. Suddenly humans could migrate to places where it required full adult strength and cunning to extract food. They could go wherever they pleased. After all, there were older women around to help.
Supporting this proposition are the foraging patterns of the Hadza. Very young children find much of their food themselves, but they depend on adults for half their calories, and those calories come from foods, like deeply buried tubers, that only an adult can obtain. Growing old, then, may be nothing new, and the postmenopausal years worthy of celebration and gratitude. Grandma is great, she is strong, and she baby-sits for free.
-----------------------------------------------------
Grandma, revisited
My recent article about the evolutionary role of grandmothers generated a lively discussion on the message boards. Many readers used the story as an opportunity to celebrate their own grandmothers. Here’s what two of them had to say.
Grandmothers are incredible. My maternal grandmother taught me to play baseball and football (I can still hear her shout, “Hit him in the numbers!”) and introduced me to pro wresting, poker and craps. The other grandmother, a self-reliant farm woman, introduced me to the wonderful world of nature and the great outdoors. The maternal grandmother was such an unforgettable character, all the women I was attracted to — woe begone! — later in life were very, very much like her. — Posted by Charles Downey
I had two wonderful grandmothers and thought of them as I read this. One survived all her children and the other survived all but one and lived to be 103. Both of these women were terrific role models and certainly fit the picture of grandmothers helping younger members of the family - emotionally and physically. I also thought of my daughters now entering menopause, active and vibrant women a little troubled by this change. If we continue to refer to menopause as ‘the change,’ let’s make sure we understand and give voice to the knowledge that it’s a positive change! — Posted by Molly
Several readers were insulted by the notion that scientists saw fit to develop an evolutionary theory about women after their reproductive years.
Why do we need scientific studies to validate that women are valuable even when they cannot reproduce? The implicit assumption in all this is that a woman’s purpose is to reproduce, and it’s necessary to find a reason for her to survive past her childbearing years….A productive person is important to society at large no matter where she is on her life continuum. We are worthwhile because we are human, not because we’re useful to evolution. — Posted by N.W. Clerk
Others were bothered by the fact that my story suggested Grandma is doing a disproportionate share of the work.
Why are we celebrating the fact that 60-year-old women are working as hard as 20 year olds? How does that imply status or respect? What are the 60-year-old men doing? Since most traditional societies are patriarchal, I bet they are enjoying their status as elders who no longer have to toil to maintain their place in the family. — Posted by T.K. Hicks
And finally, some readers noted that for many grandchildren, grandma is only half the story.
Not to take anything away from grandmothers but let us not overlook grandpa’s acquired wisdom. — Posted by joe fox
------------------------------------------
One of the losses that an industrialized culture experiences is the demise of the multigenerational family structure, the support systems inherent in that structure. We gain, however, chosen communities and families - that may consist of various generations. There are pros and cons to each structure... Think about it. Talk about it.
BTW: Joe? By taking the time to make your comment, and making us take time away from thinking about grandma... you are indeed taking something away from the grandmothers. A discussion about a marginalized group is always having something taken away from it when people bring in comments about the non-marginalized group. Grandfathers, in a patriarchal society, have had many many studies done about them... they are inevitably referred to as "elders." Perhaps we should de-gender our language completely when referring to people as a group? Both men and women of the grandparent persuasion can be referred to as elders? Only if they both carry out the same duties in their roles as they serve society. We are all servants (and owners) of society, we are referred to as citizens. But... elders are still citizens, right? Are we taking something away from them by not including that in their title? See how much this train of thought has derailed the original discussion? It is about the historical, evolutionary induced, role of elderly females on their culture and survival. This is NOT a discussion on anything else, especially not the impact of this evolutionary heritage on today's culture and survival... Right?
![[identity profile]](https://www.dreamwidth.org/img/silk/identity/openid.png){kind=small}
no subject
Date: 2007-10-27 08:30 pm (UTC)no subject
Date: 2007-10-30 06:15 pm (UTC)Yes, absolutely.
(An open letter from Ms. So Pale She's Almost Translucent to my fellow European-Americans: could you all please stop with the "but what about white people?" questions in situations like the one above? It's not like we as a group have been historically underrepresented.)