Thursday, 21 Aug, 2008 Science

Want to Live Longer - Get a Second Wife


For those who want to live longer there's more than just controlled diets, green tee and long walks. According to the latest research the key to a longer life lies in polygamy. The new study showed that men from polygamous cultures live longer than those from the monogamous cultures.

Virpi Lummaa, an ecologist at the University of Sheffield, UK, said that by estimating the socio-economic differences it was found that men from 140 countries that practice polygamy live by 12 percent longer than men who live in 49 countries that mostly practice monogamy.

The findings could answer the question on why men live so long. However, this question can only make sense after scientists ask the same for women, who live longer after menopause than nearly all other animals. One of the answers lies in a phenomenon dubbed grandmother effect. A woman gains 2 grandchildren for every decade she survives past the menopause.

Researchers believe that by loving and spoiling their grandchildren, as well as thinking about furthering some of the genes, women live longer after menopause. In contrast to women, men can be fertile in their 60s and even 80s. Scientists consider that such ability can explain why men live long.

Together with her colleague Andy Russell, Lummaa tried to find other factors that could explain the longevity of men, such as grandfather effect. In order to test this possibility, researchers analyzed records for 25,000 Finns that lived in the 18th and 19th centuries. These records were preserved by local churches.

Most people moved little, and did not use contraception and the Lutheran Church enforced monogamy. Only a widowed man could get married for a second time, and in case he had children with his new wife, in average the two fathered more children than those who were married once. However, in the end remarried men "don't end up with any more grandchildren," said Lummaa.

"If anything the presence of a grandfather was associated with decreased survival of grandchildren," she said. Probably the kids of the first mother fail to benefit from food and resources that go to the children of the second mother. "It's kind of the Cinderella effect."

The grandfather effect proved to be a wrong supposition, pushing the two scientists to the idea that the constraints of human physiology might explain the longevity in men. Male longevity could be a result of biological selection for women who live longer.

By using the information provided by the World Health Organization, the two researchers found 189 countries on monogamy scale 1 to 4 (totally monogamous to generally polygamous). Lummaa and Russell also took into consideration the GDP and average income of each country in order to minimize the effect of improved nutrition and healthcare in Western countries with monogamous culture.

If male longevity depends on female survival then both monogamous and polygamous men would live for about the same period of time. However, Lummaa and Russell found that fathering more children with several wives increases male longevity. Thus men live longer because they are fertile well into their 60s, 70s and 80s.

Men who carry on fathering their children into their 60s and 70s might take better care for their bodies due to the fact that they have mouths to feed. However, the forces of evolution may also choose for longer-lived men in polygamous societies.

"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," said Chris Wilson, an evolutionary anthropologist at Cornell University in Ithaca, New York.

Source: NewScientist

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