According to Science Daily recent research (to be published in Proceedings of the Royal Society, Biology) indicates that Toxoplasma gondii may have some interesting effects on human culture:
“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.”
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.
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.
H’mmm, I wonder what would happen if somebody got infected by a hairworm?
On a more serious note, this raises some interesting questions. Toxoplasma gondii changes a rats’ behavior (via altered neurtransmitter function) so that it is more likely to be eaten by a cat. In humans, Toxoplasma gondii has been implicated in a in a wide variety of disorders. Additionally, their is some other evidence that Toxoplasma gondii also affects the personality of the infected but I have never seen this applied in a context of culture change (from the Science Daily article):
“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.”
There’s a master’s or Ph. D. dissertion in studying the effects of parasites on culture change…
Added Later: That’s what I get for not paying attention. Carl Zimmer at the Loom has intersting posts on Toxoplasmosis and Ampulex compressa – a wasp that parasitizes cockroaches.