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Study: May-December Romances Good for Human Race
Tuesday, September 18, 2007
Older men who shack up with much younger women keep the Grim Reaper at bay
for the human population and extend our species' lifespan, new research
claims.
Even beyond movie stars and Playboy's Hugh Hefner, there is a tendency for
older men to partner with younger women, according to the study, published
in the Aug. 29 edition of PLoS ONE.
In less developed, traditional societies, males are about 5 to 15 years
older than their female partners. In the United States and Europe, guys are
an average of two years senior to their partners.
More interestingly, when older men father children, their genes seem to
increase the lifespan of both sexes over evolutionary time.
How it works
Women often lose their reproductive capacity around age 50, but if men can
still reproduce into their 70s, Darwin would say it's advantageous for males
to live longer lives providing they can hook up with a woman capable of
reproducing.
Natural selection should favor longevity-boosting genes, which would get
passed down from fathers to both sons and daughters. So women would benefit
as well in future generations, the scientists say.
Result: Over time, the older-guy-with-younger-gal lifestyle would lift the
lifespan ceiling for both men and women in the next generations and so on.
"By increasing the survival of men, you have a spillover effect on women
because men pass their genes to children of both sexes," said study team
member Cedric Puleston, a doctoral candidate at Stanford University.
Anthropologist Cheryl Jamison of Indiana University, who was not involved in
the research, called the results "fascinating."
Wall of death
From an evolutionary perspective, women who can no longer reproduce are
non-players, and since it takes two, men partnered with menopausal women are
also irrelevant.
Following that idea, natural selection should select for harmful mutations
that impact women after menopause.
Over time, the discriminating genes would accumulate in the population,
causing what evolutionary biologist William Hamilton called the "wall of
death," in which mortality of women spikes at the onset of menopause.
Population records and everyday observations indicate that's not the case.
Life expectancy for men and women in today's industrialized countries is 75
to 85 years, with mortality increasing gradually, not abruptly, following
female menopause.
Men matter
To figure out whether male fertility could help explain human longevity,
Shripad Tuljapurkar of Stanford University and his colleagues examined
lifespan and fertility data from both men and women.
They studied four societies thought to closely mimic the lifestyles of our
ancestors, including two hunter-gather groups, the Dobe !Kung of the
Kalahari Desert in southern Africa and the Ache of Paraguay (one of the most
isolated populations in the world), as well as the Yanomamo forager-farmers
of the Brazilian Amazon and an indigenous group in Bolivia called the
Tsimane.
The research team also looked at farming villages in the West African nation
of Gambia and a group of modern Canadians.
In all six groups, women stopped having children on average by their 50s,
while some men continued to reproduce. The average age after which men
showed no reproduction varied among the groups:
- Canada: Men showed fertility until 55 years old.
- !Kung: 55 years old
- Gambia: 75 years old
- Yanomamo: 70 years old
- Ache: 65 years old
- Tsimane: 60 years old
Mate choices
Until now, the most popular explanation for the bounty of over-55s, called
the "grandmother hypothesis," suggested women get a life extension in order
to care for their children and grandchildren.
The new findings don't contradict that hypothesis, but help explain how men
give women another boost over the "wall of death."
"I don't think the finding conflicts with the grandmother hypothesis but
rather that it can be considered along with it as explanations for human
longevity - there doesn't have to be a single gene or single selective
factor," Jamison told LiveScience.
But why do men choose younger mates and females prefer older men?
"There is a lot of evidence from evolutionary psychology that men are
seeking younger women and women are seeking older men," said anthropologist
Martin Fieder of the University of Vienna, who was not involved in the
current study.
Cases in point: At the age of 26, Anna Nicole Smith married 89-year-old
Jeremiah Howard Marshall II. In 1995, actor Tony Randall, then 75, married
and had two kids with Heather Harlan, who was 24 at the time. Last month,
90-year-old Nanu Ram Jogi from India reportedly became the world's oldest
father when he announced his 21st child.
Evolutionary psychologists argue that older men have more resources to
protect and care for the family, while younger, more fertile women give
their male partners better means of passing along genes.
In a study of about 10,000 Swedish men and women, Fieder and his colleagues
have found that men had the most children if they were partnered with women
about six years younger than themselves.
So the benefits of "age-defying" couples go both ways. Plus, the human
species gets a boost.
Study: May-December Romances Good for Human Race
Tuesday, September 18, 2007
Older men who shack up with much younger women keep the Grim Reaper at bay
for the human population and extend our species' lifespan, new research
claims.
Even beyond movie stars and Playboy's Hugh Hefner, there is a tendency for
older men to partner with younger women, according to the study, published
in the Aug. 29 edition of PLoS ONE.
In less developed, traditional societies, males are about 5 to 15 years
older than their female partners. In the United States and Europe, guys are
an average of two years senior to their partners.
More interestingly, when older men father children, their genes seem to
increase the lifespan of both sexes over evolutionary time.
How it works
Women often lose their reproductive capacity around age 50, but if men can
still reproduce into their 70s, Darwin would say it's advantageous for males
to live longer lives providing they can hook up with a woman capable of
reproducing.
Natural selection should favor longevity-boosting genes, which would get
passed down from fathers to both sons and daughters. So women would benefit
as well in future generations, the scientists say.
Result: Over time, the older-guy-with-younger-gal lifestyle would lift the
lifespan ceiling for both men and women in the next generations and so on.
"By increasing the survival of men, you have a spillover effect on women
because men pass their genes to children of both sexes," said study team
member Cedric Puleston, a doctoral candidate at Stanford University.
Anthropologist Cheryl Jamison of Indiana University, who was not involved in
the research, called the results "fascinating."
Wall of death
From an evolutionary perspective, women who can no longer reproduce are
non-players, and since it takes two, men partnered with menopausal women are
also irrelevant.
Following that idea, natural selection should select for harmful mutations
that impact women after menopause.
Over time, the discriminating genes would accumulate in the population,
causing what evolutionary biologist William Hamilton called the "wall of
death," in which mortality of women spikes at the onset of menopause.
Population records and everyday observations indicate that's not the case.
Life expectancy for men and women in today's industrialized countries is 75
to 85 years, with mortality increasing gradually, not abruptly, following
female menopause.
Men matter
To figure out whether male fertility could help explain human longevity,
Shripad Tuljapurkar of Stanford University and his colleagues examined
lifespan and fertility data from both men and women.
They studied four societies thought to closely mimic the lifestyles of our
ancestors, including two hunter-gather groups, the Dobe !Kung of the
Kalahari Desert in southern Africa and the Ache of Paraguay (one of the most
isolated populations in the world), as well as the Yanomamo forager-farmers
of the Brazilian Amazon and an indigenous group in Bolivia called the
Tsimane.
The research team also looked at farming villages in the West African nation
of Gambia and a group of modern Canadians.
In all six groups, women stopped having children on average by their 50s,
while some men continued to reproduce. The average age after which men
showed no reproduction varied among the groups:
- Canada: Men showed fertility until 55 years old.
- !Kung: 55 years old
- Gambia: 75 years old
- Yanomamo: 70 years old
- Ache: 65 years old
- Tsimane: 60 years old
Mate choices
Until now, the most popular explanation for the bounty of over-55s, called
the "grandmother hypothesis," suggested women get a life extension in order
to care for their children and grandchildren.
The new findings don't contradict that hypothesis, but help explain how men
give women another boost over the "wall of death."
"I don't think the finding conflicts with the grandmother hypothesis but
rather that it can be considered along with it as explanations for human
longevity - there doesn't have to be a single gene or single selective
factor," Jamison told LiveScience.
But why do men choose younger mates and females prefer older men?
"There is a lot of evidence from evolutionary psychology that men are
seeking younger women and women are seeking older men," said anthropologist
Martin Fieder of the University of Vienna, who was not involved in the
current study.
Cases in point: At the age of 26, Anna Nicole Smith married 89-year-old
Jeremiah Howard Marshall II. In 1995, actor Tony Randall, then 75, married
and had two kids with Heather Harlan, who was 24 at the time. Last month,
90-year-old Nanu Ram Jogi from India reportedly became the world's oldest
father when he announced his 21st child.
Evolutionary psychologists argue that older men have more resources to
protect and care for the family, while younger, more fertile women give
their male partners better means of passing along genes.
In a study of about 10,000 Swedish men and women, Fieder and his colleagues
have found that men had the most children if they were partnered with women
about six years younger than themselves.
So the benefits of "age-defying" couples go both ways. Plus, the human
species gets a boost.
