From the FYI file: infection by a common parasite, Toxoplasma gondii, can actually change your behavior. You may be more familiar with this critter as the cause of Toxoplasmosis, and the source of the old wives’ tale about pregnant women avoiding cats. (The parasite lays its eggs in the digestive system of cats, and contamination of food by cat feces can cause infection in humans.)
The ability of parasites to control the behavior of their hosts, although icky and weird, is hardly a new idea in the science biz. For example, the orb spider, Plesiometa argyra, is infected by a parasitic wasp that causes it to weave special, wasp-friendly webs before dying gruesomely. Additionally, the barnacle Sacculina will infect the nervous system of crabs, causing them to care for the barnacle’s eggs. If a male crab in infected, it will become protective and maternal towards the alien eggs. (These things and more can be found at Damn Interesting, which is, not surprisingly, damn interesting.)
…but back to our story. It turns out that while Toxoplasma lowers the IQ of men, making them more likely to take risks, be anti-social, jealous, and just generally more bastardly, the effect in women is completely different. Infection makes women more outgoing, friendly and promiscuous. The human results are similar to those observed in mice, and served to increase the chance that the parasite would be able to infect other mice. When infected mice were treated with medication, the behaviors ceased.
Makes you wonder if you mind is really your own, doesn’t it? Also, you can insert your own stupid Republican joke here. I trust you.