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Of Mice and Macho Men | by jurvetson
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Of Mice and Macho Men

Went to go visit baby mama, the feral cat that spawned Keeper & Co., and she was very affectionate today. She casually knocked back a couple rodent poppers and then wanted some attention from the humans.


She rubbed up against my legs as I was reading New Scientist about the latest research on microbes that can hijack their hosts and turn them into zombies.


I knew of the ant-infecting fungus from Daniel Dennett’s TED talk on mental infections that coopt their hosts in deeply profound ways for purposes of propagating the parasite. He then drew the analogy to religion in humans, and I thought perhaps these brain infections happened only in the domain of mimetics, a cognitive snow crash of sorts.


Then I read about the cats:


Toxoplasma gondii is a parasitic protozoan that most commonly infects rodents, either via raw meat or cat faeces. Once inside its host, the parasite develops to maturity without causing any real harm, but to complete its life cycle it must find its way into the gut of a cat. To do this, it increases the dopamine levels in the host's amygdala, the region of the brain associated with fear. This seems to make danger pleasurable and, before long, the reckless rodent puts itself in harm's way and is eaten by a cat, placing the parasite exactly where it needs to be for its continued survival.

T. gondii can also infect humans. Over the past decade researchers have noticed that populations where many people are infected with the protozoan have different behavioural characteristics than those where toxoplasmosis is relatively rare.

For example, infected men tend to be more dogmatic, less trusting of others, less respectful of rules, more jealous and more wary than the non-infected. The effects are subtle and might not be apparent to an observer or even to infected individuals, says Kevin Lafferty at the University of California, Santa Barbara. Nevertheless, he has been exploring the possibility that they may explain some cultural differences between men from different parts of the world (Proceedings of the Royal Society B). "To say that toxoplasmosis makes men more macho may be oversimplifying it, but it is definitely associated with neurotic behaviour, which is related to strongly differentiated gender roles," he says.

This is intriguing, given how T. gondii makes rodents more reckless. Is the parasite also manipulating humans to its own ends - and if so to what benefit? Alongside intensifying gender roles, the protozoan causes infected individuals to have longer reaction times, leading to an increased risk of traffic accidents (BMC Infectious Diseases). Lafferty speculates that by impairing alertness, the parasite may once have made ancient humans easier prey for big cats, allowing it to complete its life cycle using humans, not rodents, as an intermediate host.”

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Taken on August 19, 2011