http://www.newscientist.com/article/dn14564-polygamy-is-the-key-to-a-long-life.html...
Polygamy is the key to a long life
a.. 17:26 19 August 2008
b..
NewScientist.com news service
c.. Ewen Callaway
Want to live a little longer? Get a second wife. New research suggests that men
from polygamous cultures outlive those from
monogamous ones.
After accounting for socioeconomic differences, men aged over 60 from 140
countries that practice polygamy to varying degrees lived
on average 12%% longer than men from 49 mostly monogamous nations, says Virpi
Lummaa, an ecologist at the University of Sheffield,
UK.
Lummaa presented her findings last week at the International Society for
Behavioral Ecology's annual meeting in Ithaca, New York.
Rather than a call to polygamy, the research might solve a long-standing puzzle
in human biology: Why do men live so long?
This question only makes sense after asking the same for women, who - unlike
nearly all other animals - live long past the
menopause.
Enforced monogamy
One answer seems to be a phenomenon called the grandmother effect. For every 10
years a woman survives past the menopause, she gains
two additional grandchildren, Lummaa says. It seems that doting on and spoiling
grandchildren aids their survival, as well as
furthering some of their grandmother's genes.
Men, by contrast, can reproduce well into their 60s and even 70s and 80s, and
most researchers assumed this explained their
longevity. But Lummaa and colleague Andy Russell wondered whether other factors
explained the long lifespan of men, such as a
grandfather effect.
To test this possibility, the team analysed church-gathered records for 25,000
Finns from the 18th and 19th centuries. People tended
to move little, no one practiced contraception and the Lutheran Church enforced
monogamy.
Only widowed men could remarry, and if they had children with their new wife,
they fathered more kids, on average, than men who
married once.
But ultimately remarried men "don't end up with any more grandchildren," Lummaa
says. "If anything the presence of a grandfather was
associated with decreased survival of grandchildren."
Perhaps, Lummaa adds, the children of the first mother lose out on food and
resources that go to the second mother's kids. "It's
kind of the Cinderella effect."
Even fathers with only one wife provided no benefit to their grandchildren, a
finding supported by previous research.
Biological selection
With the grandfather effect ruled out, Lummaa and Russell next wondered whether
the constraints of human physiology explain male
longevity. In the same way that men have nipples that evolved for women to
nourish their young, male longevity might be a
consequence of biological selection for long-lived women.
To answer this question, the researchers compared the lifespan of men from
polygamous countries with those from monogamous nations.
Using data from the World Health Organization, Lummaa and Russell scored 189
countries on a monogamy scale of one to four - totally
monogamous to mostly polygamous. They also took into account a country's gross
domestic product and average income to minimise the
effect of better nutrition and healthcare in monogamous Western nations.
Lummaa stressed that their monogamy score is a crude first stab, and they are
working to find multiple ways to assess marriage
patterns. The conclusions could evaporate under further analysis, she adds.
If female survival is the main explanation for male longevity, then monogamous
and polygamous men would live for about the same
length of time. Instead, it seems that fathering more kids with more wives leads
to increased male longevity. Men, then, live long
because they're fertile well into their grey years.
The explanation could be both social and genetic. Men who continue fathering
kids into their 60s and 70s could take better care for
their bodies because they have mouths to feed. But evolutionary forces acting
over thousands of years could also select for
longer-lived men in polygamous cultures.
"It's a valid hypothesis and good prediction," says Chris Wilson, an
evolutionary anthropologist at Cornell University in Ithaca,
New York, who attended the talk. But the care and attention of several wives who
depend on the social status of their ageing husband
could explain everything. "It doesn't surprise me that men in those societies
live longer than men in monogamous societies, where
they become widowed and have nobody to care for them."
--
Frederick Martin McNeill
Poway, California, United States of America
mmcneill@
fuzzysys.com
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"I never cease being dumbfounded by the unbelievable things people believe."
- Leo Rosten
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