Now it is the parasite's fault:
It sounds like an absurdly grand claim, but toxoplasma, a protozoan, is such strange organism that it might not be entirely crazy. When the parasite infects the brains of rats and mice, it alters their behavior, making them more reckless than normal--reckless enough that they don't avoid cats the way good sense would dictate. As a result, they're devoured, at which point the micro-organisms are able to reproduce--something they can only do in felines. Then their eggs are excreted, and any mammal that eats something contaminated with the cat feces takes up the toxoplasma eggs. A rat, for example, who then begins to act reckless...and so on.
And because toxoplasma infection is actually quite common in humans, and varies from one region to another--about a third of Americans show antibodies to the parasite, but in Brazil the number rises to nearly 70%, while in South Korea it's under 5%. And those differences, suggests the study's author, could explain, at least in part, why people from different nationalities have developed differently along cultural lines. Lafferty acknowledges there are all sorts of factors that contribute to such traits, but argues that this tiny parasite could be one of them. And, he says, it's not necessarily a bad thing since, as he notes in the release, it adds to cultural diversity.
