Sharp Rubber Duck

Cat Parasite runs the world, Parasite,
    culture link suggested

August 17, 2006

By Mike Taugher
Contra Costa Times

Jose Carlos Fajardo/Times

A cat parasite, Toxoplasma gondii, can affect human behavior, a study suggests. Research Kevin Lafferty says societies with a high rate of infection tend to be more rigid, with less gender equality.

A common cat parasite that infects humans may be linked to male dominance and the makeup of cultures, a researcher's study suggests.

Societies with a high rate of infection tend to be more "neurotic," with more rigid structures and greater division of gender roles, according to the study.

The provocative study, published in the respected Proceedings of the Royal Society, Biology, compared infection rates of the parasite Toxoplasma gondii in various countries with sociological descriptions of those countries. It revealed a relationship between the frequency of the parasite and some cultural traits.

Study author Kevin Lafferty of the U.S. Geological Survey said the link might have something to do with the parasite's ability to affect the behavior of rodents. Toxoplasma gondii alters the brain chemistry of rodents, making them more active, bolder and less afraid of cats.

The parasite's effect on rodents is an evolutionary advantage because it is only when a cat eats an infected rat that the Toxoplasma enters feline intestines, where it can reproduce. More active, less fearful rats have more fatal encounters with cats and Toxoplasma lives on.

Previous personality studies have shown the parasite also appears to affect humans, and Lafferty, an ecologist who specializes in parasites, set out to determine whether its effects might exhibit themselves more widely in cultures where many humans are infected.

Because the parasite is common and women of child-bearing age are often tested for it, he was able to gather a lot of information about infection rates. Then he collected sociological studies that characterized cultures.

Western nations with high infection rates tended to have more "macho" cultures with more differentiation in gender roles. They also tended to exhibit "uncertainty avoidance," or a fear of risk that led to more rules, laws and organized religious institutions.

It is possible something else could explain the association between infection rates and cultural traits, Lafferty said. For example, the parasite thrives in certain climates and so perhaps something about the climate in those countries explains how society is shaped.

But he asserted that the effect of parasites on people is a better explanation.

Lafferty acknowledged that the findings will be greeted with skepticism by cultural anthropologists and others, adding that it makes sense that biological factors could influence how societies are shaped.

"I'm going to guess that cultural anthropologists are going to look at this paper and say, that's interesting, but personality doesn't define culture," Lafferty said.

But, he said, "The data all support the hypothesis that Toxoplasma can (influence) culture."

One Toxoplasma expert said it has not been established that the parasite affects people.

"It definitely affects the brain in mice. In man, nobody knows," said Jitender Dubey, a microbiologist at the U.S. Department of Agriculture in Beltsville, Md.

Still, Lafferty said several personality studies have shown that personalities are affected by the parasite, with men and women affected differently.

Citing those studies, he wrote that infected women "are more intelligent, rule-conscious, dutiful, conscientious, conforming, moralistic, staid, rule-bound, warm, outgoing, attentive to others, kindly, easy-going and participating."

Infected men, on the other hand, tend to be "less intelligent and more reflective, rigid, loyal, stoic, slow-tempered, frugal, reactive emotionally, changeable, affected by feelings, emotionally less stable and easily upset."

"These associations suggest that the effect of T. gondii on culture could be broader than postulated here," Lafferty wrote.

The U.S. infection rate, like that of Scandinavian countries, is relatively low, which is consistent with the study's prediction of more gender equality and a society willing to take risks, Lafferty said.

Other countries, such as Brazil, have high infection rates that are exhibited in the societies there.

Lafferty said one important question raised by the study's findings is whether there is any need to try to reduce infection rates. Brazil, he said, has a wonderful culture.

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