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ToddStark
August 7th, 2006, 12:56 PM
Reported in Science Daily (http://www.sciencedaily.com/releases/2006/08/060804085444.htm)

Source: University of California - Santa Barbara


Cat Parasite May Affect Cultural Traits In Human Populations

A common parasite found in cats may be affecting human behavior on a mass scale, according to a scientist based at the University of California, Santa Barbara.

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While little is known about the causes of cultural change, and biological explanations often stimulate social and scientific debate, a new study by the U.S. Geological Survey published in the August 2 issue of the Proceedings of the Royal Society, Biology, indicates that behavioral manipulation of a common brain parasite may be among factors that play a role.

"In populations where this parasite is very common, mass personality modification could result in cultural change," said study author Kevin Lafferty, a USGS scientist at UC Santa Barbara. "The geographic variation in the latent prevalence of Toxoplasma gondii may explain a substantial proportion of human population differences we see in cultural aspects that relate to ego, money, material possessions, work and rules."

Although this sounds like science fiction, it is a logical outcome of how natural selection leads to effective strategies for parasites to get from host to host, said Lafferty. Toxoplasma gondii is a parasite of cats, both domestic and wild. While modern humans are a dead-end host for the parasite, Toxoplasma appears to manipulate personality by the same adaptations that normally help it complete its life cycle. The typical journey of the parasite involves a cat and its prey, starting as eggs shed in an infected cat's feces, inadvertently eaten by a warm-blooded animal, such as a rat. The infected rat's behavior alters so that it becomes more active, less cautious and more likely to be eaten by a cat, where the parasite completes its life cycle. Many other warm-blooded vertebrates may be infected by this pathogen. After producing usually mild flu-like symptoms in humans, the parasite tends to remain in a dormant state in the brain and other tissues.

Evidence for subtle long-term effects on an individual's personality, reported by researchers in the Czech Republic, inspired Lafferty to explore whether a shift in the average, or aggregate, personality of a population might occur where Toxoplasma has infected a higher proportion of individuals. Infection with Toxoplasma varies considerably from one population to another; in some countries it is very rare, while in others nearly all adults are infected. To test his hypothesis, Lafferty used published data on cultural dimension and aggregate personality for countries where there were also published data on the prevalence of Toxoplasma antibodies in women of childbearing age. Pregnant women are tested for antibodies because of the serious risk posed by toxoplasmosis to fetuses, which lack their own immune systems.

The results of previous work suggested that Toxoplasma could affect specific elements of human culture. Toxoplasma is associated with different, often opposite, behavioral changes in men and women, but both genders exhibit guilt proneness (a form of neuroticism). Lafferty's analysis found that countries with high Toxoplasma prevalence had a higher aggregate neuroticism score, and western nations with high prevalence also scored higher in the 'neurotic' cultural dimensions of 'masculine' sex roles and uncertainty avoidance.

"There could be a lot more to this story. Different responses to the parasite by men and women could lead to many additional cultural effects that are, as yet, difficult to analyze," said Lafferty.

Lafferty suggested that because climate affects the persistence of infectious states of Toxoplasma in the environment, it helps drive the geographic variation in the parasite's prevalence by increasing exposure risk. The parasite's eggs can live longer in humid, low-altitude regions, especially at mid latitudes that have infrequent freezing and thawing. Cultural practices of food preparation such as rare or undercooked meats, or poor hygiene, can increase exposure to infection, as can having cats as pets. Lafferty added, "Toxoplasmosis is one of many factors that may influence personality and culture, which may also include the effects of other infectious diseases, genetics, environment and history. Efforts to control this infectious pathogen could bring about cultural changes."

"This is not to say that the cultural dimensions associated with T. gondii are necessarily undesirable," noted Lafferty. "After all, they add to our cultural diversity."

Margaret McGhee
August 7th, 2006, 05:38 PM
Thanks for posting this. I ran across a mention somewhere else but never read it thoroughly.

It says: Lafferty's analysis found that countries with high Toxoplasma prevalence had a higher aggregate neuroticism score, and western nations with high prevalence also scored higher in the 'neurotic' cultural dimensions of 'masculine' sex roles and uncertainty avoidance.
That causes me to think again about my previously stated guess that psychological liberal / conservatism could have inheritable components but not likely. This offers a pathogen model for such biases I hadn't considered - still not inherited, however - except maybe an inherited susceptibility or resistance to the pathogen?

It Says: Lafferty suggested that because climate affects the persistence of infectious states of Toxoplasma in the environment, it helps drive the geographic variation in the parasite's prevalence by increasing exposure risk. The parasite's eggs can live longer in humid, low-altitude regions, especially at mid latitudes that have infrequent freezing and thawing.
This fits with my own experience of finding a higher incidence of psychological conservatism among males especially in southern US where I travelled on business for many years. Returning often to my home in the pacific northwest provided a very vivid contrast - only anecdotal, of course.


I didn't really understand the statement from the article: Efforts to control this infectious pathogen could bring about cultural changes.
Are they saying that liberal / conservative personality changes may be the result of social attempts to control the pathogen rather than the effects of the pathogen itself? :confused: Oh, I think they meant to say the results of successful efforts to control this infectious pathogen could bring about cultural changes.

An additional thought: I think it is wrong to assume that conservative psychological states would always align with conservative politics - or for liberal psychological states to align with liberal politics. My own view is that a better variable for predicting the correlation of beliefs and subsequent behavior would be the tendency to harbor strong emotional beliefs at the top of one's personal belief hierarchy. The result is that one's important behavior decisions will be guided by emotions primarily from that source - and one's intellect would be used primarily to justify rather than examine those conclusions.

I suspect that in N. America such strong beliefs have mostly been held by political conservatives for the last few decades after WWII. But many events these days have convinced me that many on the political left are adopting similarly strong emotional beliefs as the higher order identity beliefs in their personal belief systems.

This was seen recently in the Gingrich revolution - a very religious-like belief in the supreme morality of conservative politics that swayed many Americans attracted to the church-meeting-like atmosphere of such righteous causes.

The liberals then were still largely bound by rationality and turned off by the hallelujahs on the right. Now it seems many formerly rational liberals have seen the light and are adopting religious-like beliefs to combat the right.

The current plight of Joe Lieberman seems to be a case in point. I'm no Lieberman fan but I do think the case against him is more emotional than rational. In this case Bush is the devil and Lieberman has supported Bush when he has agreed with him. It wasn't that much but some on the far left have become religiously opposed to the presence of Israel in the mideast. Lieberman has generally supported Bush whenever policies come up involving militant Arabs - who Bush generally sees as the devil.

I guess I'm saying I still don't see eveidence that strong liberal or conservative outlooks are inherited - but that the tendency to hold strong emotional beliefs in one's mind that are often expressed as strong liberal or conservative biases in politics - could well be.

Margaret

Fred H.
August 8th, 2006, 12:17 PM
From Wiki—
The Pathogenic hypothesis of homosexuality, or the gay germ hypothesis, argues that a pathogenic cause of homosexuality is pointed to by the reduced number of offspring produced by homosexuality, meaning evolution would strongly select against it, by the low identical twin concordance for homosexuality, which further argues against genetic influence, and by analogue with diseases that alter brain structure and behavior, such as narcolepsy, which are suspected of being triggered by viral infection. It is inaccurate to refer to this hypothesis as a theory, as a theory represents a well-tested and verified hypothesis that has withstood all currently possibly scientific scrutiny and inquiry.

Gregory Cochran, who has generated attention for his ideas in evolutionary medicine and genetic anthropology, and Paul Ewald, professor of biology at Amherst College, have advocated a number of pathogenic theories of disease, and conclude that this is a "feasible hypothesis". They do not assert that there is sufficient evidence to show that it is factually correct. As of 2005, no experiments or studies have yet been attempted. At present, it is a speculative hypothesis. (Crain, 1999)

Rationale—
Cochran points out that conditions which strongly affect the ability to reproduce fall into two categories - those that are very rare (affecting about 1 in 10,000 births or less), and those that result from genes which actually confer evolutionary advantage in certain situations, and disadvantage in others. (Such as sickle cell anemia.) Homosexuality is reportedly present in more than 1 in 100 people. Assuming it is not caused by a recent mutation, and that it does not fall into the selective advantage category, a reasonable explanation would be that it is caused by a germ or other environmental factor.

Cochran claims that theories of the cause of narcolepsy - that it is an auto-immune disease triggered by a virus - make the mechanism of selective brain modification plausible. He also claims that only humans and sheep exhibit homosexual behavior at population levels near 1% or greater. He says that given their physical proximity, it would be plausible to expect a pathogen that affected both species.

Proponents cite the cases of the bacterium Helicobacter pylori, which was recently discovered to contribute to most peptic ulcers; the bacterium Chlamydia pneumoniae, which may cause atherosclerosis; Nanobacter, which might cause kidney stones; and various viruses linked to cervical cancer and hepatocellular carcinoma (liver cancer). (Crain, 1999)
Of course there are those that are distressed by such an hypothesis, seeing it as “pathologizing homosexuality.” But really, MM, Carey, Tom, and Todd, let’s face it: Natural Selection is a bitch.