Article headline is ridiculously overstated. How about: "Cat Parasite Has Some Odd Psychological Effects In People Who Are Infected By It, And So Probably Had Some Minor Influence On Cultural Evolution, Which Isn't Really All That Surprising, If You Think About It".
He meant that the 'people that have heard this' have no idea. I'm not sure whether his sentence can be properly interpreted as such, but even if it's grammatically dubious, the intention is clear (to me). He probably knows that the effect is vastly overstated in popular accounts, as other commenters have pointed out.
I think the labeling of it as a cat parasite is interesting but misses the mark a bit. By messing with rat brains it helps feed cats. From the cat's perspective, it can sound more like a symbiotic relationship.
The title of the article (not this post) is outrageous! "Cat Parasite Affects Everything We Feel and Do"
Even the content of the article itself disagrees with the title:
"He's not suggesting that it's a big player in cultural evolution. Lots of other things are more powerful, ranging from geography to weather to the availability of natural resources."
And that's the "popular account". Consider what the actual research paper probably said. Reminds me of this comic:
That's why I toned it down -- I still thought it was cool, though. Apparently the parasite evolved by convincing rats that cats smell like fun, because it needs to make it to a cat's stomach to reproduce.
