Half the human race has a brain parasite that changes your personaltiy and makes men sexier. UPDATED

This is a bigger story than climategate.  The parasite that causes toxoplasmosis  changes who you are and is found in the brains of half the human race. With it, testosterone and dopamine levels rise. So does anxiety and how each sex copes with it.  This isn’t breaking news and the documention is sound.

“How your cat is making you crazy”  McAuliffe’s stunning review in the Atlantic is a must read about Toxoplasma Gondii.   She references studies by Sapolsky, Vyas, Flegr, Webster and McCloskey.  Material below is adapted from that article.  It's a two page story. Read them both.  It's a cat story because parasite reproduction only happens inside the guts of a cat.

-"Men with cat litter disease are manlier".  (Caveat: They may not have got it from their cats.  h/t Instapundit.)

-"Infected women tended to be more meticulously attired, many showing up for the study in expensive, designer-brand clothing. Infected men tended to have fewer friends, while infected women tended to have more."

-Schizophrenia is more common among the infected and may run in families, not because of genes but because of pussy cats.

-Genes carried by the parasite promote dopamine production in their hosts.  Dopamine is a normal part of everyone’s brain chemistry.  It  influences pleasure centres and takes the edge off pain. 

-Infected men find the smell of cat pee relatively okay and infected women find cat pee smell particularly offensive. The result was absent when dog, horse, hyena and tiger urines were substituted in the sniff test.

-The response to anxiety and risk changes but differently in men and women.  This has been tracked at the level of “national character” and in small groups. Infected  men told to drink a mystery liquid raised strong objections while subject females who were carrying the parasite swallowed compliantly.

Though found in other mammals, T. Gondii reproduces in cat intestines and only there.   In our relatively sanitary country, people who handle cat litter are more likely to pick up the parasite, but it’s found worldwide.   Male rats who get it find that cat pee smells sexy to them.  Turned on, they fearlessly approach cats who dine on them  and pass on T. Gondii to sex heaven in the feline bowels.   The survivors are sexier than the rest. 75% of the infected females would rather spend time with an infected male.

And a teaser at the end of the Atlantic article: Flu shots have the same chemicals as live virus infections.  A single small study showed people given flu shots doubled their social contacts during the few days when the real flu would have been most infectious.  They got the idea it would be nice to go to a pub or have people over to visit at twice the rate of the days before and after.  Holy Hannah!  (It’s a single small study with 36 subjects.  If you do an internet search, the other stories seem to piggyback on the same underlying report.  That is not the case with the Toxoplasma Gondii  research.)  Then there's the example of animals infected with rabies that bite other animals to infect them just before dying themselves.

McAuliffe points out stomach ulcers had a similar story.  Until it was shown that treating  the bacteria made the disease go away, most people pooh-poohed the idea even twenty years ago.

From Proceedings of the Royal Society:  Can common brain parasite influence human culture.  (yes).

From the  Center for Disease Control.  Infection rates in the US.

UPDATE:  Wall Street Journal expands with "The Virus In Your Genes"   MS and a virus built into your personal genome.  Interesting.